ill! Ill mmm il THE DIATOMACEAI. PRINTED BY W. E. BAXTER LIMITED, LF.WES AND LONDON. p / A TREATISE ON THE DIATOMACE^ containing Introductory Remarks on the Structure, Life History, Collection, Cultivation and Preparation of Diatoms, and A Description and Figure typical of every known Genus, as well as a Description and Figure of every Specils found in the North Sea and Countries bordering it, including Great Britain, Belgium, &c\ BY DR. HENRI VAN HEURCK, Piofcssor of Botany and Director at the Antwerp Botanical Gardens ; Hon. F.J?. M.S. and New York JAN.. and Author of the " Synopsis des Diatomdes de Belgique" &c. 'z: L/8ftAf?v)S, gHJu*trcttefc ln> about 2, GOO £ia.uve#. translated by WYNNE E. BAXTER, F.R.M.S., F.G.S. goufcem : William Wesley & Son, 28, Essex Street, Strand, W.C. 1896. &rd& (?5^, '^gf. <^>ea?c&if -Aetccac^ Author's Preface. The Synopsis, the last part of which was published in 1S85, had the good fortune to meet with so favourable a reception by diatom- philes that the work was promptly subscribed, and, in consequence, its selling price increased considerably. Its present enhanced value, and the fact that only a few copies are now available, prevents all but those with considerable means from acquiring it. Under these circumstances it has occurred to the Author that it would be useful to publish a work, in some respects more limited, and at such a price as to be within the reach of all persons of average means. The scope of the present Treatise includes all the information of which we can be certain concerning the Life History and Structure of Diatoms. It also comprises a description of every genus that can with reason be admitted at the present time, as well as of every species that has been hitherto found in the North Sea, and of those more commonly found in the countries abutting thereon, viz. : — Great Britain, the extreme north of France, Belgium, Holland, Denmark and Norway. Under these conditions it is hoped that the Work will be found useful, not only to those who merely devote themselves to a general and summary examination of diatoms, but also to those who desire to determine the species found within this area. It is essential that a book of this nature, to attain its object, should contain a large number of figures ; and, consequently, although as many Synopsis-figures as possible have been made use of, several hundred others have been added. The fact that all these have been reproduced on a moderate scale by the process of phototypography, has enabled greater clearness to be attained than in the Synopsis, whilst keeping the price within moderate limits. vi. author's preface. Every effort has been made that the work should present as faithful a conspectus as possible of all the forms found within the prescribed area; but, notwithstanding, it is greatly feared that a certain number of them has escaped the Author's notice. The Author requests the readers of this Volume to be good enough to inform him of any omissions they may discover, so as to enable him to insert them in the French Edition, which he hopes to publish shortly. Mr. Wynne E. Baxter, who is himself a skilful Diatomist, has been good enough to translate this work, and publish it for the benefit of English diatomphiles. He has performed this task with every possible care, and with his usual ability. Both amateurs and the Author owe a debt of gratitude to Mr. Baxter for the great sacrifice at which he has published the Work. H. V. H. Botanical Gardens, Antwerp, \gf/i September, 1896. Translator's Preface. The last general work on the Diatomaceae published in English is that by Mr. Rails as published in Pritchard's Infusoria in 1861, while that on the Diatomaceae ot Great Britain is the classical work of Professor Wm. Smith, which made its appearance more than 40 years ago. Under such circumstances, the publication of the present work appeared to be opportune, aiming as it does at a complete figured classification of genera, bearing the stamp of the authority of the Author's great experience, together with a description and illustrated synopsis of all species found in Great Britain and the neighbouring shores ; and this view has been corroborated in a most encouraging manner, by the fact that more than half the Edition has been subscribed previous to publication. The geographical distribution of species described have been largely noted from published lists ; and my own collection, amounting to upwards of 10,000 preparations (including the life-work of that versatile and indefatigable diatomist, the late Mr. Frederick Kitton), has enabled me to supplement the records of previous authors. The Index of species and genera, which contains references to the Analytical Contents, and to the figures in the plates and text, has been compiled so as to render reference to any particular species as easy as possible, and at the same time to prevent readers from being confused by synonyms. It was originally intended to have incorporated a full list of the Diatomaceous Deposits found in the British Isles, but the unexpected length of the Work has not only considerably delayed the date of publication, but has also rendered this object unattainable. My thanks, however, are due to many correspondents who have so readily assisted me in its compilation, and it is hoped that its publication is only deferred. Vlll. TRANSLATOR S PREFACE. In spite of the fact that most of the leisure hours of a somewhat busy life have, during the last three years, been devoted to this work and that every care has been exercised in testing the many references, it is feared that errors, both of translation and reference, will be found, to which it is hoped readers will extend their generous indulgence. The Author has referred to the Translator's work in terms of unjustifi- able eulogy. The latter, however, feels that no English amateur, with any enthusiasm, will be able to refrain from admitting that this admirable work, with its elaborate tables and carefully conceived diagnoses, modified to meet the requirements of the student of our country, places us all under great obligations to the great Belgian Diatomist. W. E. B. 170, Church Street, Stoke Newington, London, N. 1st October, 1896. CONTENTS. Frontispiece — Apparatus used for making Marine and INTRODUCTION. CHAPTER I. Structure and Life History of Diatoms i. Structure 2. Movement 3. Multiplication and Reproduction Study of Diatoms . Workroom Artificial Illumination Instruments — Microscope ,, Accessory Appjratus . Drawing and Determining Species Collecting Diatoms Collecting inland Marine and Pelagic Collections Collecting from Fossil Deposits „ Marine Deposits ,, Guano Deposits ,, Lacustrine Deposits . Cultivation of Diatoms Ordinary Cultivation of Fresh Water Diatoms Artificial Cultivation of Marine Diatoms Pure Cultivation of Diatoms Mr. C. Houghton Gill's Cultivations Results of Experiments with Cultivations Teratology of Diatoms Preparation of Diatoms Prof. H. L. Smith's Method Mr. Fredk. Kitton's Method Mr. J. Kinker's Method . Prof. Brun's Method Preparation with Styrax and Liquidambar Preparations in very Refractive Liquids CHAPTER II. Terminology and Classification of Diatoms Frustule Valves Raphe and Nodules Endochrome Table of the Pfitzer Petit Classification Classification adopted in this Work . Of Genus and Species Pelagic Gatherings. Page 1 1 9 13 24 24 24 25 28 28 29 29 39 42 42 42 43 43 46 47 48 5° 52 55 65 67 71 73 74 76 77 83 83 84 92 94 95 97 98 39544 Page . 104 . T04 . 1 10 . 111 • JI3 . 121 . 122 CONTENTS. CHAPTER III. Bibliography ..... General Bibliography .... Collections of Diatoms .... Collections used for this Work Special Bibliography of the British Isles Table of Names of Authors and Collectors cited Unit of Measurement .... DESCRIPTION OF GENERA AND SPECIES. Sub-Family I. — Raphidie^ • • .125 Tribe I. — Cym belled . . . . 125 Genus 1. Amphora Ehr., 1831 . . . -125 Okedenia Eul. in litt = Amphora inflcxa H. L. Sm. Genus 2. Cvmbella Ac, 1830, Char. Em. . . . 140 Cymbella Ag. . 1830 — frustules free. Cocconenia Ehr., 1829 — fruslules stipitate. Syncyclia Ehr., 1835 — frustules arranged in a circle. Genus 3. Encyonema (Ktz., 1833), H.V.H. Emend, 1885 . 148 Tribe II. — Navicule^; . . -152 Genus 4. Mastogloia Thwaites, 1848, Char. Em. . . 153 Genus 4a. Stigmophora Wallich, i860 . . -156 Genus 5. Dictyoneis Cleve, 1890 . . . . 157 Genus 6. Stauroneis Ehr., 1843, Char. Em. . . . 158 Staurogramma Rab. , 1853 — valves with decussating striae. Staurosigma Grun., i860 — valves with sigmoid raphe. Pleurostauron Rab., 1859 — frustules cohering in filament. Endostauron Grun. , 1868 — frustules enclosed in mucous tubes. Genus 7. Navicula Bory, 1822 .... 162 Alloieneis Schum., 1867 — striae of unequal length on the two sides of the valve. Anomneoneis Pfitz. , 1871 — corresponding with the group Sadptece of this work. Caloneis Cleve, 1891 — valves indistinctly punctate, with striae crossed by longitudinal lines. Craticula Grun., 1868 — valves anomalous, showing transverse costae. Diadesmis Ktz., 1844 — Navicula united in long bands. Dickieia Berk., 1844— scattered frustules in a plane frond Diploneis Ehr., 1840 — valves constricted at the median portion. Falcatella Rab., 1853 — a medley of forms with arcuate valves. Libellus Cleve, 1873 — frustules with connective membrane showing numerous plicae. Neidium Pfitzer, 1871— corresponding with the group Affines of this work. Pinnularia Ehr., 1840 — valves with beads confluent into costae and consequently showing continuous striae in the form of canililuli. Rhaphidodiscus Th. Christian, 1887 — genus founded either on the accidental superposition of a Navicula and Melosira or on certain disciform Navicula. Schizonema Ag., 1824 — Navicula enclosed in mucous tubes. Schizostauron Grun., 1867 — Navicula furnished with a pseudo- stauros, bifurcated in the form of a St. Andrew's Cross. Stauroptera Ehr., 1843— Navicula having a pseudo-stauros. Stictodesmis Grun., 1863, and Perizonium Cohn and John, 1862 — Navicula with craticular transverse costae. Trachyneis Cleve, 1893 — corresponding with the group Aspereceol this work. ? Cyclophora Castr. , 1878 — valve having a median (craticular?) annulus. CONTENTS. XI. Genus 8. Genus 9. Genus 10. Genus 1 1. Genus 12. Genus 13. Genus 14. Genus 15. Genus 16. Genus 1 7. Genus 18. Genus 19. Genus 20. Genus 21. Genus 22. Genus 23 Genus 24. Genus 25. Genus 26. Genus 27. Genus 28. Genus 29. Genus 30. Genus 31. Page Rhoiconeis Grun., 1863 .... 238 Cymatoneis Cleve, 1894 . . . 238 COLLETONEMA (BREB., 1849), H. VAN HEURCK, 1S85 . 238 Van Heurckia Breb., 1868, Char. Em. . . 239 Stenoneis Cleve, 1894 . . . .241 Cistula Cleve, 1894 , . .241 Amphipleura Ktz., 1844 .... 242 Reicheltia H. Van Heurck, 1895 . . . 243 Gomphopleura Reichelt, 1894. Brebissonia Grun., i860 .... 244 Rouxia J. Brun. & Herib., 1893 . . 244 Berkeleva (Grev., 1827), H. Van Heurck, T885 . 245 k.iphidoglcea Ktz., 1844= Berkeleya in a globular frond, frustules arranged in fusiform rows. Scoliopleura Grun, i860 .... 246 Scoliotropis Cleve, 1894. Toxonidea Donkin, 1858 .... 247 Donkinia Ralfs., i860 .... 248 Pleurosigma W. Sm., 1853 .... 249 Pleurosigma W. Sm. partim — stria? decussating. Gyrosigma Hassall, 1845 — strire rectangular. Rhoicosigma Grun., 1867, Em. Perag., 1891 . . 260 Amphiprora (Ehr.), 1843, Cleve, 1891 . . 261 Tropidoneis Cleve, 1891 . . . 263 1. Orthotropis Cleve, 1S91. . . . 263 2. Plagiotropis Pfitzer, 187 1 . . . 264 3. Amphoropsis Grun., 1883 . . . 266 Auricula Castr., 1873 .... 266 Tribe III. — Gomphono-me/E . . . 268 Gomphonema Ag., 1824, Char. Em. . . . 268 Sphenella Ktz., 1844 — frustules free. Gomphonema Ag., 1824 — frustules stipitate. Sphenosira Ehr. , 1843 — frustules united in filaments. Gomphonella Rab. , 1853 — frustules enclosed in an amorphous gelly. Gomphoneis Cleve, 1894 — valves furnished with costte alternating with beads. Rhoicosphenia Grun., i860 Tribe IV. — Achnanthe^ ACHNANTHIDIUM (KTZ.) GRUN., l88o . Achnanthes Bory., 1822 .... Achnanthidium Ktz., 1844 — frustules united in an amorphous gelly or free. Monogramma Ehr., 1843 — frustules with a transverse line on one of the valves. Cymbosira Ktz., 1844 — frustules united, end to end, in rows. Tribe V. — Cocconeide,e Orthoneis Grjn., 1868, Em. Grun., 1880 275 276 276 277 283 283 XII. CONTENTS. Genus 32. Anorthoneis Grun., 1868, Em. Cleve, 1893 Genus 33. Campvloneis Grun., 1863 . Genus 34. Cocconeis (Ehr., 1835) Grun., 186S . Sub-Family II. — Pseudo-Raphidie/e Page . 284 • 285 . 286 Cohort I. — FraylariinecE . Tribe VI. — Epithemie^e Genus 35. Epithemia Breb., 1838 Cystopleura Breb. , 1849. Rhopalodia Otto Muller, 1895. Genus 36. Eunotia Ehr., 1837, Char. Em. Himantidium Ehr., 1840 — frustules united in long bands. Amphicampa Ehr., 1849 — valve having its two margins dentate, fur- ther divided by Ehrenberg into : — ■ Ophidocampa Ehr. , 1869 — valves with indentations equal and alternate on the dorsum and venter. Heterocampa Ehr,, 1869 — valves inflated in the middle. Climacidium Ehr., 1869 — Eunotia with girdle face quadrangular, valves with dorsal margin dentate, truncate, and apices rounded. Desmogonium Ehr., 1848 — Eunotia elongated, apices generally inflated, arranged in bands or united in a long filament at the apices. Genus 37. Pseudo-Eunotia Grun., 1865 and 1882 Genus 38. Ceratoneis Ehr., 1840 . . . . Genus 39. Actinella Lewis, 1863 Desmogium Eul. Tribe VII. — Synedrea; Genus 40. Synedra, 1831, Char. Em. .... a. Eusynedra H.V. H., 1865 — valves with continuous striae, without sulci. b. Ardissonia De Not., 1870 — -strise interrupted by sulci. c. Toxarium Bail. , 1853 — valve very narrow, but much enlarged at the middle and apices ; without strice, but with irregular puncta. Genus 41. Campylostylus Shadb., 1849 Thalassionema Grun. in Synop., 1863 — frustules united in filament or stellate, valve bordered with coarse beads. ? Pseudo-synedra Leud.-Fort. — forms incompletely known: further examination necessary. Genus 42. Asterionella Hass., 1850 . Genus 43. Thalassiothrix Cleve & Grun, 1880 Tribe VIII. — Fragilarie^e Genus 44. Fragilaria Lyngbye, 1819, Char. Em. Grammonema Ag. , 1836 — frustules scarcely silicious. Staurosira Ehr. , 1841 — Pseudo-raphe broad, valve often inflated at ihe middle. Ralfsia O'Meara, 1875 — Valves hyaline. Genus 45. Cymatosira Grun., 1862 . Genus 46. Campylosira Grun., 1862 , 292 293 293 294 298 3°5 3°5 306 3°7 3°7 318 320 321 322 323 327 327 CONTENTS. Mil. Genus 47- Genus 48. Genus 49. Genus 5o. Genus 51- Genus 52. Genus 53- Genus 54- Genus 55- Genus 56. Genus 57- Genus ^ bis Genus 58. Genus 59- Genus 60. Genus 61 Genus 62 Genus 63 Genus 64 Genus 65. Genus Genus 66. 67. Tribe IX. — Raphoneide/e a. Symmetrical. Clavicula Pant., 18S6 Terebraria Grev., 1864 Raphoneis Ehr., 1844 Doryphora Ktz., 1844 — frustules stipitate. b. Asymmetrical (Tracliyspheniacece P. Pttit). Trachysphenia Paul Petit, 1877 sckptroneis ehr, 1 844 Grunoviella H. Van Heurck, 1892 . Peronia Breb. & Arn., 1868 Opephora Paul Petit, i 888 Tribe X. — Plagiogramme^:. Glyphodesmis Grev., 1862 . Omphalopsis Grev., 1863 . DlMEREGRAMMA RALFS., i860, CHAR. Em. Tubularia Brun., 1894 Plagiogramma Grev., 1859. Cohort II — Tabeltariinece Tribe XI. — Entopyle^e Eutopyla Ehr., 1841 Eupleuria Arnott, 1858 (synonymous). Gephyria W. Arnott, i860 Tribe XII. — Licmopherea: Licmophora Ac, 1827, Char. Em. Rhipidophora Ktz.. 1844— frustules stipitate, girdle face obovate lanceolate. Climacosphenia Ehr., 1843 Tribe XIII. — Meridione^e Meridion Ag., 1824 Tribe XIV. — Diatome^e Diatoma De Candolle, 1805, Char. Em. Odontidium Ktz., 1844 — frustules united in short bands, costse very robust. Ralfsia O'Meara, 1875 — valves hyaline, without costje = Fragilaria. Denticula Ktz., 1844, Char. Em. Tribe XV. — Tabellarie^e A. Only two jalse septa. DlATOMELLA GREV., 1 855 . . . . Grammatophora Ehr., 1839 Page ■ 328 328 • 329 329 33i JO '- 332 333 334 334 335 335 337 ■~* "> <-l JO/ 338 338 339 34° 34i 34i 345 347 347 348 348 35i 352 353 353 XIV. CONTENTS. B. More than two false septa. a. Fossil or fresh water forms. Genus 68. Tabellaria Ehr., 1839 .... Genus 69. Tetracyclus (Ralfs, 1843) Grun, 1862 Salacia Pant., 1889 — valves elliptic, lanceolate. Goniphogramma Braun, 1852 — valves elliptic, frustules united by twos or threes. Genus 70. Stylobiblium Ehr., 1845 b. Marine forms. Genus 71. Rhabdonema Ktz., 1844 .... Genus 72. Climacosira Grun., 1862 .... Genus 73. Striatella Ag., 1832 .... Hyalosira Ktz., 1844— septa appearing alternately interrupted at their apex. Tessella Ehr., 1838 — septa interrupted in the middle of their length. Genus 74. Lamella Brun., 1894 .... Cohort III. — Surirellineaz .... Tribe XVI. — Surirelle^e Genus 75. Podocystis Ktz., 1844, Char. Em. Euphyllodium Shadb. , 1853 — costas anastomosing. Genus 76. Hydro-silicon Brun., 1891 Genus 77. Cymatofleura W. Sm., 185 i Genus 78. Surirella Turpin, 1827 .... Stenopterobia Breb. in litt. — frustules narrow, elongated, sigmoid. Calodiscus Rab., 1853 — valves orbicular or sub-orbicular, without median line. Plagiodiscus Grun. and Eul., 1868 — valves reniform, with radiant costae (anomalous forms). Campylodiscus Ehr., 1841 Cohort IV. — Nitzschiinece . Tribe XVII. — Nitzschieve Hantzschia Grun., 1877 . Nitzschia (Hassall, 1845 5 ^ M- Smith) Char. Em., Grun., 1880 . . . . Bacillaria Gmel. , 1788 — frustules in tablets or in oblique rows. Tryblionella W. Sm., 1853 — valves undulate, septate, with carina indistinctly punctate. Pritchardia Rab., 1863 — carina with puncta prolonged into costas, striae alternately prolonged. Perrya Kitton, 1874 — carinal dots prolonged into long interrupted lines. Grunowia Rab., 1864 — dots prolonged into transverse or dimidiate costas. Nitzschiella Rab., 1864 — valves with apices very attenuated (flexed). Homoeocladia Ag., 1827 — frustules enclosed in mucous tubes. Genus 82. Gomphonitzschia Grun., i8c8 Tribe XVIII. — Cylindrothece^e Genus 83. Cylindrotheca Rab., 1859 Page 356 357 359 359 360 361 362 364 364 364 365 366 366 .168 Genus 79. Genus 80. Genus 81. 375 380 380 380 382 408 409 409 CONTENTS. XV. Genus 84. Sub-Family III. — Crypto- Raphidie/e • Tribe XIX. — Chtetocere.e I. (a) Rhizosoleniece. Rhizosolenia (Ehr. Brightwell) Per. Em. 1892 Henseniella Schutt, 1893 — frustules flexed. (b) Dactyliosolencce. .Genus 85. Dactyliosolen (Castr., 1886) Char. Em. Perag., 1892 Genus 86. Guinardia H. Perag., 1892 Genus 87. Lauderia Cleve, 1873 Dotonula Schutt, 1893 — spines absent on the surface of the disc. Genus 87^ Perag alloa Schuti-, 1895. (t) Altheyea. Genus 88. Attheya West, i860 1 1 . Eu- C/iietocerece. Genus 89. Ch/Etoceros Ehr. (1844) Char. Em.. Chcetoceros Auct. — valves with awns not arranged in a circle on the margin of the valves. Bacteriastrum Shadb. , i860 — valves plane, bearing a circlet of hori- zo ital awns Corethron Castr., 1886 valves convex, furnished with a corona of erect spines Ditylum Bailey, 1861 Syndetoneis Grun., 1888 . Pyrgodiscus Kitton, 1885. Dicladia Ehr., 1844 (spore of chcetoceros ?). Thaumatonema Grew, 1863. Syringidium Ehr., 1845 Syndendrium Ehr., 1845 (spore of chcetoceros?). Hercotheca Ehr., 1S44 . 95. Goniothecium Ehr., 1844 . Tribe XX. — Melosire^e Page . 410 . 412 4i3 416 4i7 418 419 420 420 Genus 90. Genus 91. Genus 92. Genus 93- Genus 94. Genus 9S- Genus 96. Pyxilla (Grev., 1864) H.V.H., 1893. Pyxilla Grev. — apiculus simple. Kenttodiscus Pant., 1889 — apiculus covered with sm spines. Pterotheca Grun., 1883 — apiculus laterally alate. Genus 97. Ktenodiscus Pant., 1889 . Genus 98. Peponia Grev., 1863 Genus 1,9. Strangulonema Grev., 1865 Genus 100. Syndetocystis Ralfs, 1864 Genus 101. Rutilaria (Grev., 1863) Grev., Em., 1866 Genus 102. Clavularia Grkv., 1865 . . ' scattered 422 423 424 425 426 427 427 428 429 43° 43° 43 < 431 432 433 433 XVI. CONTENTS. Page ■ 434 435 436 437 437 437 43§ Genus 103. Stephanopyxis Ehr., 1844, Char. Em. Cresswellia Grev. , 1857 (spines coronal). Trochosira Kitton, 1871 — central processes or spines not numerous. Genus 104. Muelleriella H. Van Heurck, 1894 Genus 105. Thalassiosira Cleve, 1892 Genus 106. Skeletonema Grev., 1865 Genus 107. Stephanogonia Ehr., 1844, Char. Em. Genus 108. Pantocsekia Grun., 1886 . Genus 109. Melosira Ac, 1824, Char. Em. Orthosira Thw. , 1848 — frustule with puncta surface plane, dentate. Aulacosira Thw., 1848 — joints cylindrical, bisulcate. Gaillonella Bory, 1823 — valves carinate. Paralia Heib. , 1863 — valve punctate and areolate. Liparogyra Ehr., 1844 — valves with internal thickenings. Genus iio. Endyctia Ehr., 1845 .... 445 Genus in. Cyclotella Ktz., 1833 . . 445 Genus 112. Podosira Ehr., 1840 . . . 447 Genus 113. Druridgea Donkin, 186 1 . . . . 448 Genus 114. Hyalodiscus Ehr., 1854 .... 448 Genus 115. Centroporus Pant., 1889 . . . 449 Tribe XXI. — Biddulphie/e. I. — Isthmiece. Genus 116. Isthmia Agardh, 1830 . . . . 451 II. — HemiaulidecB. Genus 117. Terpsinoe Ehr., 1843 .... 452 Pleurodesmium Ktz., 1846 — Frustules united by short processes, like feet. Tetragranima Ehr., 1843 — valve furnished with four costce. Genus 118. Hydro-sera Wallich, 1858 . . . 453 Genus 119. Anaulus (Ehr., 1844) Char. Emend. . . 454 Eunotogramma Weisse, 18154 — valve lunate. Genus 120. Helminthopsis H. Van. Heurck, 1892 . . 455 Genus 121. Hemiaulus (Ehr., 1844) H. L. Smith Em. . . 455 Corinna Heib., 1863 — valve cuneate, with two unequal processes. Trinacria Heib., 1863 — valve triangular, with three processes. Solium Heib., 1863— valve quadrangular, with four processes. Genus 122. Ploiaria Pant., 1889 .... 457 Genus 123. Graya Brun & Grove, 1892 . . . 458 Genus 124. Pseudo-Rutilaria Grove & Sturt, 1886 . . 459 Genus 125. Rutilariopsis H.V.H. 1894 . . 459 Genus 126. Baxteria H.V.H. , 1893 .... 460 III . — Euca?npie nil i J- G' C Fig. i. Ideal Section of a Navicula, \ l ) See Mr. Julien Deby's excellent paper : Ce que c'est qu'une Diatome'e in the Bulletins de la Socidte" Beige de Microscopie for the year 1877. HISTORY OF DIATOMS. varying thickness, which is generally considerable at the ends of those diatoms whose axis is prolonged. The cellular membrane is transparent and, as in all vegetable cells, is formed at the expense of the primi- tive protoplasmic mass. It does not adhere intimately to the valves because the use of even the weakest re-agents suffices to make it con- tract by forcing its contents towards the centre of the frustule. The endochrome (fig. i CC) is of a golden or brownish yellow and sometimes, but rarely, of a greenish colour, as in the case of Navicula cuspidata. The endochrome is arranged either in granules (as in the cylin- drical and discoid forms) or else in plates, which are now sometimes called chromatophores. The chromatophores do not always form continuous bands ; they are occasionally jagged and perforated in a most peculiar way, and this is the case with many marine diatoms. n a ex Ivc I 'CsVe°OS * /$3/ 7" 4o 3 S I \\ \II\ III JV J'Aj/axrant/iifie \ — \- ii I Or&n coloring matter OBQ Fig. 3- Spectra given by certain diatoms and by chlorophyl (after P. Petit. Copy Engraving belonging to R.M.S. ) I. Chlorophyl of higher plants. 3. Pxycoxanthin extracted from diatoms. 3. The green colouring matter (chlorophyl) of diatoms. 4. 5. °. 7. Spectra of the endochrome of various diatoms. HISTORY OF DIATOMS. 7 of alcohol at 900. Thus the two colouring elements are isolated, and it only remains to evaporate the solvents to obtain the elements in a solid state. The plate on the preceding page represents the spectra of various kinds of endochrome which have been obtained by Mr. Petit in a pure state, compared with the spectra of chlorophyl. Petit's researches are very important, but according to an anonymous critic, published in a note in the English Mechanic, they are incomplete. At the time when Petit published his work, says the critic, he was unacquainted with the long and important paper published by Sorby in 1873 on the colouring materials of the vegetable kingdom. U) It is shewn in Sorby's paper that certain colouring materials which had, till then, been considered simple, could be separated into many others. Thus the phycoxanthine of Petit, which is identical with the phy- coxanthine of Kraus, consists of the yellow xanthophyl of Sorby with the addition of chlorofuchsine, true fucoxanthine and lichnoxanthine, the whole being slightly stained by the presence of a little chlorophyl (which is itself a compound substance) (2) and of a very small quantity of phycoxanthine. We must refer the reader who desires to study these different substances to Sorby's paper, as this subject cannot here be exhaustively treated. It will be sufficient for the diatom student to know that diatomine is extremely analogous to the chlorophyl of higher plants, and that like it, it decomposes the carbonic acid of the air under the influence of solar light, rejecting the oxygen, and assimilating the carbon. It is in consequence of this action that diatoms are able to perform the impor- tant function of purifying water. The valves of diatoms assume every variety of shape and form ; they are, as a rule, mutually symmetrical, slightly convex on the outside and (') On Comparative Vegetable Chromatology, by H. C. Sorby. Proceedings of Royal Society, N. 146, June, 1873, pp. 442-483. (3) The green colouring matter of higher plants, according to Sorby (op. cit. ), is of very complex composition and that in leaves taken from the shade differs from that in those exposed to the sun. In the leaves of Aucuba Japonica, for example, Sorby found what he called "blue chlorophyl," "yellow chlorophyl," "orange chlorophyl," and "mixed chlorophyl,'' in which latter again he detects " yellow xanthophyl " and "lichnoxanthine." The latest researches of the French chemists, Messrs. Fremy and Arm. Gautier, have not pronounced it of so complex a composition ; Mr. Arm. Gautier has shewn that the chlorophyl is a distinct substance, crystallizing in intensely green flat needle-like crystals, which are slightly acid. By oxidizing or deoxidising the chlorophyl a variety of derivative salts of yellow, green, red, and brown colours can be formed. When digested in warm concentrated hydrochloric acid, it divides into two substances ; the one which is insoluble in this liquid, but forming a brown solution in warm alcohol or ether, is the phylloxanthine of Fremy ; while the other, which is of a bluish green hue, has acid properties and is the phyllocyanic acid (which he formerly called phyllocyanine) of the same author. 8 THE STRUCTURE AND LIFE concave on the inside. When examined with good objectives of sufficient resolving power and in media of high refractive index, all, or nearly all, appear ornamented with designs or stria? running in different directions. The best objectives, however, show that these stria? are illusory, and that in reality they are alveoles in the thickness of the valves (J), the regular arrangement of which gives the appearance of stria?. Many diatoms show an increase in the thickness of the valves, either at the centre of figure alone, or, in addition to this, at the two extremities; this increase of thickness is called a nodule (fig. 4). These nodules are often connected together by a longitudinal line called a raphe or median line. When the nodule in the centre is considerably enlarged so as to spread laterally over all or part of the valve, the name of stauros is substituted for that of nodule. The stria? do not always occupy the whole surface of the valve ; they are very often absent near the median rib, and also round the central nodule, where their absence may give rise to the semblance of a stauros ( pseudo-stauros) . The unstriated part of the valve is called by English diatomists the white or blank space, for which expressions Manoury has proposed to sub- stitute that of mcsorhabde. The mesorhabde, which is faint or absent in nuny diatoms, is highly developed in others, such as Navicula cardinalis, lata, &rc. In this work we have invariably used the terms zone or hyaline area when referring to this plain portion of the valve. The surface of the valves is called the valve or valvular face or side view of the frustule or simply the valve ; and the part of the frustule corresponding with the connecting zone is called the frontal face, frotit, girdle or zonal view or principal face. Some authors (Rabenhorst, &c.) have reversed the terms principal face and lateral face, and we should greatiy approve of their idea if it were not for the confusion which would necessarily result now that the previous terms having been used by such eminent authors as Kutzing, Smith, Gregory, Greville, &c, have been generally adopted. It is preferable to select the expressions valve face and girdle or zonal face, which can leave no doubt in the reader's mind. These words which we proposed in the third edition of our work on the Microscope have been generally adopted, and we shall continue to employ them. ( ' ) It was generally assumed, until recently, that the valves of diatoms were covered with hemi- spherical beads in relief. We shall show hereafter that these so-called beads are cells hollowed out of the thickness of the valve. We shall nevertheless continue to use the words beads, striae, and costae, after fixing their true meaning, as they have passed into common use, and to abandon them would introduce confusion in the descriptive part. HISTORY OF DIATOMS. 2. Movement of Diatoms. — A large number of diatoms, especially those which have a naviculoid form, are endowed with the power of locomotion, the cause of which is not yet ascer- tained, and which has exercised the imagination ot a large number of observers. Of the numberless hypotheses which have been put forward to explain the motion of diatoms, that which has been advanced most frequently is the supposition of the existence of cilia ; this is also the suggestion of Mr. Jacob D. Cox, of Cincinnati, one of the most learned diatomists of our age, in a small work (J) recently published by him. Mr. J. D. Cox believes that the raphe is the seat of a line of cilia, which act in the groove formed by the raphe, and which Prof. H. L. Smith declares to be a genuine cleft. The narrow line of epidermis at this spot being covered with active cilia, one can easily understand, says Mr. Cox, that the formation of silica on this line would be obstructed or hindered. Still more recently Mr. O. Biitschli, (2) Professor of Zoology at Heidelberg University, has revived the idea of a cilium or very fine flagellum, and thinks that by means of it the phenomenon under consideration can be explained. Unfortunately, up to the present no staining re-agent whatever has been discovered which will throw these filaments into relief so that their existence has never been demonstrated. Professor H. L. Smith has for a Ions; time studied the motion of diatoms with great care. We cite below a passage from a letter, in which this scientist describes some interesting phenomena which he was able to observe during the movement of certain diatoms. " If a living Finnularia is followed under the microscope after the field has been coloured blue by indigo, and when the valve side is in view, that is to say, with the median line turned towards the eye, small particles of indigo will be observed to move along the whole length of the median line, and then to accumulate near the centre in the form of a small ball or sphere. Fig. 4. Navicula viriais. A. Valve or valve face. B. Girdle or zonal face. (') Diatoms, their nutrition and locomotion, by Jacob D. Cox, in The Microscope, July, 1890. (2) Mittheilung iiber die Bewegung der Diatomeen. Heidelberg, 1892. IO THE STRUCTURE AND LIFE ™^y- ,.0 "If viewed on the girdle face (fig. 5) a ball is seen to form in the centre of -/"> I each valve at a and a', and c —»*" "'N^ it is remarkable that each **X- 5- of these small spheres spin round on its axis just as if a small jet of water was being whirled over it from a small opening situated at the central apex of the median line at the point c of figure 6. " When the balls have attained a certain volume they suddenly burst, and the particles of indigo move off, following the direction of e and c (fig. 5). Immediately after the rupture of the ball, a new one commences to form in the same place. The particles ■ follow the directions e, c (fig. 5), while the diatom itself moves in the opposite direction indicated by the arrow d. If the movement of the diatom be reversed, the particles of indigo follow a path opposite to that shewn in the figure. I have observed this curious phenomenon for hours together, and I can assure you that it is a glorious spectacle. I had in the field of the microscope some magnificent specimens of large Finnuiaria, and the phenomenon showed itself very distinctly when the free movement of the frustule was arrested by a grain of sand or other , obstacle. The colour used by me was an ordinary water colour, indigo blue paint, s' sufficient being used to make the water fairly dark. Another observation which I made at the same time established to my mind the existence of a hyaline gelatinous envelope, external to the frustule, which prevented the particles of indigo coming in contact with the silicious part. When the diatom moved, it pushed before it string of indigo particles which always remained at the same distance from the front portion of the frustule, as is indicated in figure 6 d, and which was pushed out of the way during the movements of the diatom. " A very slight application of red aniline (fuchsine) proved decisively the existence of this gelatinous and usually invisible envelope, for it coloured it distinctly, even before the tint had appeared in the field of the microscope. The aniline always instantly stopped all movement of the diatoms with which it came into contact." Mr. Otto Midler also has for a long time carefully studied the movement of diatoms. We are convinced that we can give no better idea of the opinions of Mr. Muller than by translating a short resume which our HISTORY OF DIATOMS. II learned and skilful correspondent has been good enough to draw up for this work. From his recent investigations on the mechanical causes of their motion Mr. Otto Miiller concludes that the movements of diatoms must be regarded as produced by the resultant of motive forces which are generated on the surface of protoplasmic currents. His theory contains the mechanical basis of these movements, and clearly brings out its essential particulars in the following manner: — Mr. O. Muller ( ' ) in the first place proves the existence of a very compli- cated system of c.maliculi and anastomosing fissures which run across the side of the valve of the largest species of Pinnularia, and must be regarded as designed to conduct a fluid medium from the interior towards the external side of the cell. The central and terminal nodules are sulcated by straight and curved canaliculi, which run towards the raphe and are lost in it. In addition to this Mr. Muller has shewn that the lithoplasm has a considerable internal pressure. According to him, in consequence of this pressure the living plasm starts out through the canaliculi of the central and terminal nodules, and runs into and courses down the whole length of the raphe against the external surface of the cellular wall, so as to return by the canaliculi of the terminal or central nodules into the interior of the cell. The re-action of the motive forces, at the surface of the living plasm, upon the surrounding medium is the cause of the movement of the frustules. At the surface of the Pinnularia are seen four courses of currents (two on each valve). Each of them is independent in this sense, that of itself the current can proceed from a terminal to the central nodule or inversely, or can even momentarily stop. This gives rise to a great variety of force combinations, and consequently of directions of movements since the dis- placement is produced in the direction of the resultant of all the motive forces which simultaneously act in the courses of the currents. The par- ticulars of their displacement, their backward and forward motion, their deviations from the straight line, &c, are easily explained by basing them on the preceding considerations. As a rule, a plasmatic current starts from each side of the polar cleft of the anterior terminal nodule (the notions of back and front being derived from the direction of the movement) moves towards the central nodule and returns by the anterior opening of the central nodule into the interior of the cell. Outside of the posterior opening of the central nodule, there starts on (') Otto Miiller: Durchbrechungen der Zellwand in ihren Beziehungen zur Ortsbewegung der Bacillariaceen. Berichte d. Deutsch. Bot. Gesellsch, 1889, Bd. VII., pp. 169 — 180. 12 THE STRUCTURE AND LIFE either side, a second current, which returns by the polar cleft of the posterior nodule. In this case the motive forces act in the same direction, and the cell moves forward in a direction opposite to the current. If, on the other hand, the currents issue at the same time from the polar clefts towards the openings of the central nodule, then the motive forces equilibrate and the frustule remains stationary. In this way an explanation is given of the extraordinary movements of foreign corpuscles down the length of the raphe, which movements have been described by Max Schultze ('). On the other hand O. Biitschli (2) and R. Lauterborn (3) explain the movement of the large Pinnularia {major, nobilis, viridis) by an abundant production of coleoderm. They placed the frustules in an emulsion of Chinese ink and observed a current of isolated corpuscles which were directed towards the central nodule down the whole length of an envelope of coleoderm. This envelope was interrupted near the central nodule, and there brought together the ink corpuscles which, as they came together, ended by forming a kind of filament which lengthened out backwards. They also assume that in this spot there is a filament of coleoderm projected, which, by its re-action against the moving water, brings it to a standstill. Mr. Otto Muller (4) (s) confirms, it is true, these observations but rejects the conclusions they would draw from it. Often, and notwithstanding a rapid movement, the presence of a filament cannot be demonstrated, so that for this reason the movement cannot be attributed to the projection of a filament. According to Mr. Muller, the filament is only formed by the momentary stopping of the protoplasm when animated by a backward movement in front of the aperture of the central nodule. Moreover, by introducing oxygen into his cultures those individuals which are without coleoderm can be made to move. Mr. Muller believes that the protoplasm of the three species of Pinnularia (namely, major, nobilis, viridis) secretes a glaireous matter, which is fairly consistent and vibratory, possessing analogous qualities to that of the jelly of the conjugatae described by Klebs. The minute and light granules of Chinese ink do not succeed in penetrating into the glaireous bed. Conse- (*) Max Schultze : Die Bewegung der Diatomeen. Archit. f. Mikrosk. Anatomie Bd. i, Sep. , p. 376, taf xxiii. Bonn, 1865. (2) O. Biitschli: Bewegung der Diatomeen Verh. d. Natur. Hist. Med. Ver. zu Heidelberg, N.F., Bd. iv., Heft 5. ( 3 ) Robert Lauterborn : Zur Frage nach der Ortsbewegung der Diatomeen Berichte d. Deutsch Botan. Gesellsch (1894) Bd. xii., p. 73. (4) Otto Muller: Die Ortsbewegung der Bacillariaceen betreffend. Berichte d. Deutsch. Bot. Gesellsch. (1893) xi., p. 571. (S ) Otto Muller : Die Ortsbewegung II. Berichte d. Deutsch Bot. Gesellsch (1894) xii., p. 136. HISTORY OF DIATOMS. 1 3 quently they are displaced the whole length of the perimeter of the protoplasmic current, which is enveloped in a glaireous bed so as finally to come together in front of the anterior opening of the central nodule. There they collect together so as to form a filament by the plasm, which is stopped from time to time, and this filament is drawn out by the plasm as it continues to ooze out. The smaller Pinnularia and other Navicula show no signs either of a glair or filament. Nevertheless, their movement acts in the same way as in the case of the three species enumerated above. And even their anatomical structure, the system of canaliculi and fissures, as well as the arrangement of the currents which are observed in them, are in all respects identical. Consequently one is forced to conclude that the emission of the gelatinous matter is the motive agent. Midler's theory of the mechanical causes of their motion explains the displacement of these smaller species in the same manner as that of the larger, with this unique and subsidiary difference only, that the plasm of the larger species generally secretes during its movement a glaireous matter, which is not the case with the smaller species. 3. Multiplication and Reproduction of Diatoms. — Diatoms multiply by self-division and are reproduced by conjugation. When multiplying by self-division the nucleus commences by splitting up, and the division of the internal membrane takes place at exactly the same period that this phenomenon does in the cells of higher plants ; the act of deduplication of the primordial utricle is brought about with very great rapidity. It commences to show itself at the Deduplication of the' primordial utricle of tW0 ends °f the frUStule at the P°intS a Pinnularia (H. L. Smith). a an(j £ (fig- 7) . the membrane there forms a fold which gradually lengthens so as to reach the nucleolated mass in the centre about six minutes after the commencement of the phenomenon. According to Mr. Robert Lauterborn the division of the nucleus is always caryokinetic. Dr. Miquel on his part has seen in some Nitzschia the single primitive nucleus dividing into two coloured areas, each spread out like a fan, together assuming the shape of a spindle. Consequently he admits that phenomena of caryokinesis are possible in the case of diatoms. According to Dr. Miquel the division of this primordial utricle would not be brought about in the way Professor H. L. Smith indicates, but that it only commences when the nucleus is completely deduplicated, and when the nuclei which are being formed are completely separated from one another. While this sub-division is proceeding the connecting zone is correspond- ingly enlarged, and the internal membrane afterwards secretes a new silicious 14 THE STRUCTURE AND LIFE valve over each divided surface ; in the place of the primitive original frustule we therefore now find two frustules, each composed of a new and an old valve. Fig. 8 r Fig. 8' Section of a diatom at the commencement of deduplication. A. Nucleus commen- cing to divide, showing distinct nucleoles. B. Protoplasm. B.' Primordial utricle. C. Endochrome. D. Central cavities. FF.' Valves. GG.' Connecting parts. pig. g — Section of a diatom in process of deduplication. AA.' New nucleus and nucleoles. BB.' Protoplasm. BB.', Double primordial utricles. CC. Divided endochrome. DD.' Central cavities. F.' External mother valve. F. Internal mother valve. ft".' New daughter valves. GG.' Connecting parts. (J. Deby). " While the new valves are being formed," writes Mr. Deby, " They thicken and are covered with the markings peculiar to the species, and rapidly take the form and appearance of the external valves ; this secretion appears to take place from the centre towards the periphery (fig. 9). These new valves inside the original frustule occupy a more or less central position in it and face one another. " We now see the diatom made up of four valves, of which two are external and old, and two internal, close together, new and attached to the entire inside circumference of the old connecting parts ; at this period the young valves are as yet without any connecting part. " Soon afterwards, sometimes in fact before the division of the primordial utricle, it may be noticed that the connecting parts become considerably enlarged and that at the same time the interior has slid into the exterior so as to cause a greater space between the two external valves and to increase the internal cavity of the frustule. The connecting parts of the young valves are only developed later, either before or after their liberation, according to the genera and species of the diatoms. A little later, in species whose frustules are solitary, the sliding of the connecting parts attains its maximum, and the narrower frustule liberates itself entirely from the other which before was acting as a sheath to it. " From what has just been stated it follows that in the same species of diatom, according to its stage of development, individuals may be met with possessing — HISTORY OF DIATOMS. *5 i. Two valves, a connecting part and a necleus " (fig- ") , , r early stage. 2. Two valves, two connecting parts and a necleus (fig- 0 J 3. Two valves, two connecting parts, and two nuclei ] (fig. 8) 1 More or less 4. Four valves, two connecting parts, and two nuclei (fig. 10) 5. Four valves, four connecting parts and two nuclei (fig- 9) J "The external connecting part of frustules is often caducous and detaches itself spontaneously ; this is a fact which must be taken into account. advanced stage of deduplica- tion. Fig. 10. Fig. 10. Diatom [Isthmia) formed of four valves and two connecting Fig. 11. The same with two valves and one connecting part. " It is well also to notice that the protoplasm of the primordial utricle generally travels into the interior of the silicious envelope both previously to the commencement of the sub-division of the utricle and again after the termination of the phenomenon, drawing along with it the endochrome ; and also that the migrations of the colouring matter vary in their nature according to the genera and families of diatoms. While a diatom divides by binary sub-division, the endochrome also separates into two parts in order to apportion half of it to each of the two new utricles. " Every diatom frustule, it will be noticed, consists of an old valve (fig. 1 F', fig. 8 F) from the original frustule and a younger valve (fig. 1 F and fig. 8 F') of subsequent creation, whose connecting part, when it is developed, slides in the inside of the connecting part of the old valve. It follows from this that in the large majority of diatom genera where the connecting parts are of the exact breadth of the valves and are even of smaller diameter to them, every sub-division must effect a diminution in the dimensions of the new frustule equivalent to double the thickness of the connecting part. The thickness of the latter being known, it can, even a priori, be determined what will be the size of any descendant after any given number of sub-divisions." The above opinion expressed by Mr. Deby is that held by Diatomphiles for a long time, but it does not completely account for all the facts. If the x6 THE STRUCTURE AND LIFE matter is as simple as Mr. Deby has made it out to be, sexual reproduction would be very frequently observed, which, however, is not the case. Some causes not yet known must therefore occur to retard sexual repro- duction. Otto Muller has tried to investigate what are the causes of this phenomenon being so rare, and for that purpose has attentively studied a filamentous diatom, Melosira arenaria, Moore. As the frustules in this species remain united, it is possible to verify how the decrease in size comes about. (l) The following is the result of his researches :— Considered singly, individual frustules (or individual cells, if preferred) which compose a filament of Melosira arenaria, Moore, have an unequal biological value. Beyond this fact it may be remarked that in many individuals the edge of one or both valves (to the edge of which the connect- ing membrane is attached) is thickened in a peculiar manner ; this thickening is absent in other individuals. The younger valve of each frustule, up to the moment when the division commences, is without any connecting membrane, and is surrounded by the connecting membrane of the older valve. The structure of the connecting membrane, differing from that of the membrane of the valve at the lateral limits of the filament, allows a certain microscopical distinction between the, free valve (older and not covered over by a connecting zone), and the younger valve covered by the connecting zone of the older valve of the same cell. The succession, relative position and anatomical structure before mentioned of the free valves and covered valves enables a distinction to be made in the filament between groups of twin and triplet cells arranged in regular order. It can be proved in the strictest manner that the cells, the enveloped valves of which have their rims thickened, are produced by their particular ancestors as larger daughter cells ; those, on the other hand, in which this thickness is absent, are produced as smaller daughter cells. As soon as the large cells and the smaller daughter cells can be dis- tinguished with certainty, by eliminating the elements of the last formation (of the covered valves), groups of twins and triplets can be traced to their ancestor cells of the (N-i)th or the (N-2)th divisional period, and their special anatomical arrangement, and their relative situation in the filament of each period, can be depicted. If in this manner the geneological tree of the filament be reconstructed, it is then found that the smallest daughter cells, which can be easily recognized morphologically by the absence of the thickness in the edge of the younger ( « ) Otto Muller : Die Zellhaut und des Gesetz der Zelltheilungs folge von Melosira arenaria Moore. Berlin, 1883, in 8vo, with 5 plates. HISTORY OF DIATOMS. 17 valves, exactly oversteps a divisional period (generation) ; ind in this way the duration of division is retarded. As a result of what has preceded, the following law can be formulated : — "The largest daughter cell divides during the (N + i)th consecutive divisional period ; the smallest daughter cell, on the other hand, first divides during the (N + 2)th period exactly." This law not only requires that there should be a considerable delay in multiplication by division, but it also arrests the constant diminution of the cells in a marked manner ; it follows from this that the diminution in size is not carried on simultaneously with the multiplication by division, and that this diminution is only produced in a limited degree. For as far as the birth of Auxospores can be attributed to the diminution of the size of the frustules, so can the rarity of their production be explained by the phenomenon just described. The effect of the law is comprehensive ; if, for example, the diminution of size after forty-three divisions in the cells of Melosira arenaria is such that the production of auxospores becomes necessary, as must be admitted in the face of known facts, then it follows from the law enunciated that a single auxospore will be produced in the present case ; while on the other hand, if the division is effected according to the generally received rule, and as enunciated above by Mr. Deby, 1,052,100,000,000 auxospores ought to have been brought into existence. The general application of Otto Muller's law can scarcely ever be verified in solitary species, and it can only be verified in filamentous species when the smallest daughter cells of twin groups are morphologically distinguishable from the larger daughter cells, as is the case with the Melosira we have been considering. In every case each species will probably follow its own peculiar law, which we shall probably never know, because the conditions under which they have to be studied are so unfavourable. For this reason then an exhaustive knowledge of the facts which prevent the too rapid diminution of size in any given species is of special importance, and Otto Muller has rendered a signal service to science in discovering and elucidating phenomena, the existence of which had not even been suspected. One of the principal originators of Bacteriological Science, Dr. P. Miquel, Director of the Microscopical Department of the City of Paris (Montsouris Observatory), has lately turned his attention to Diatoms. Dr. Miquel has introduced into the study of these Alga? the same methods of cultivation which he has employed with such marked success in the study c rS THE STRUCTURE AND LIFE of Bacteria. For the future much time will have to be devoted to these cultivations, though Dr. Miquel has also studied the return of the reduced frustule to its largest (Sporangial) form which he has been able to bring about artificially by successive special cultivations. Dr. Miquel presented to the Academy of Sciences of Paris (24th October, 1892) a paper on this subject, which, on account of its importance, is here reproduced in its entirety : — " It is ascertained that when a single frustule of a living diatom in a free state is propagated in a sterilised and suitably nutrient maceration the daughter cells produced from the mother cell vary greatly in size. In measuring frustules of a similar cultivation it is found that the figures which represent diatoms of the same size, are approximately related to one another as the terms of the binomial expansion (1 + i)n in which n denotes the number of generations which have occurred. By taking certain diatoms of medium size from a first cultivation and transferring them to a second maceration, a second cultivation is obtained in which the size of the medium cells differs in length from that of the same diatom from some tenths to several //, according to their species. By continually producing cultivations in this way, the diatoms are made to assume very reduced dimensions, and the phenomena which accompany the re-establishment of the so-called Sporangial form are quickly observed. If the silicious Pheophyceae are associated in chains of joints the filaments, as they become smaller and smaller, should be transferred into fresh sterilised macerations, and in the same way the formation of auxosporial cells is easily promoted. " I have myself followed the re-establishment of the maximum form in Melosira and Nitzschia. " In Melosira nummuloides the protoplasm of the joint which gives birth to the so-called Sporangial frustule increases in volume, forces back the cylindro-spherical valves which contain it, slowly abandons them, and forms on their exterior an almost spherical mass, the outer covering of which immediately silicifies. This newly-formed cell soon generates by division individuals like itself, and produces a string of joints of a diameter about double that of the cylindro-spherical generating frustule. ;'The cells of Melosira varians when they have reached a sufficiently reduced size, also produce a large number of spheres, but these have diameters more than double the size of those of the generating frustules. " When these large cells have reached maturity they free themselves from the filaments and are enveloped in a thick membrane, and then the vitality of the diatom is relaxed. To all appearances these spheres constitute the spores HISTORY OF DIATOMS. l9 or sporanges of Mdosira varians. Hitherto I have not been able to observe them during their evolution. " In the case of Cxclotella comta the protoplasm, whilst increasing in volume, separates the two cylindrical valves fitting into one another, and oozes out on to the exterior in the form of a fairly regular discoid mass, the axis of which is perpendicular to that of the small frustule. The membrane containing the protoplasm then silicifies, and after deduplicating several times the newly formed Cyclotella becomes perfectly circular. " Nitzschia palea is even more adapted than the preceding species for studying the re-establishment of the maximum form of diatoms. " When the naviculoid frustules of this species have decreased in size to from 28/x to 30//, the protoplasm which they enclose is considerably distended, especially in the neighbourhood of the nucleus ; under the action of this increase of volume the valves are forced open, nearly always at one end only, and the external thalle of the diatom is rent to make way for the contents of the cell, which increases in bulk and is lengthened in the direction of the major axis of the Nitzschia and on both sides opposite the nucleus (fig. 12). This yellowish body from 65/u, to 70/x in length, containing oil globules and possessing the endochrome plates of a Nitzschia, is very irregular in form ; it has the appearance of a cylinder rounded at the ends and inflated in the centre; it may be torous, constricted, arcuate, extremely sigmoid, etc., (fig. 13) but curiously enough it is animated, and from the time of its maturity (1 fl II (i K I i 1/ 8 10 Fig. 12. 20 THE STRUCTURE AND LIFE F'g- J3- ? ™ 7n A £ c £ Fig. 14 it moves about in the maceration, often drawing in its train the two small valves of the diatom which has given it birth. The outside covering of these newly-born, large-sized Nitzschia is very soon charged with silica and covered with the striae and carinate puncta which characterise this species ; lastly, the form of this more or less abnormal species is determined by its forming increasingly rectilinear septa and by bipartition (fig. 14). " In a cultivation which is 10 c.c. (2.81525 fl. drachms) in volume many millions of cells similar to those just mentioned may often be counted. "In short, the re-establishment of the maximum form of diatoms is HISTORY OF DIATOMS. 2 1 usually accomplished in the simplest manner ; the protoplasm of each cell of smallest size swells, forces open the frustule, and escapes to the exterior enveloped in a membrane of cellulose, the presence of which may be revealed at any stage by means of reagents. Frequently the cell thus formed presents but a remote likeness to the diatom which has given birth to it ; its envelope silicifies very rapidly and becomes ornamented with the designs which characterise the genus and species ; and then, by subsequently dividing, the frustules of maximum size are rectified and regain their regularity and elegance. " The phenomenon of the re-establishment of the maximum form does not appear to be preceded by any act of fecundation ; nor is it usually the effect of conjugation. If certain diatoms do produce spores, auxospores or sporanges, this is not the case universally, for the establishment of their maximum form is usually effected without their undergoing this special modification of vegetable growth. But after all the microscope does not enable us easily to distinguish this glutinous or gelatinous matter in the midst of which, according to certain observers, diatoms germinate. " The method of cultivation which I have just described gives observers the opportunity of obtaining diatoms in their re-established form at any time, and in as large a quantity as they desire, and of witnessing under the micro- scope the different phases which precede this re-establishment." Thanks to the kindness of Dr. Miquel, who has been good enough to send me a 13th cultivation of Nitzschia palea, I have been able to examine the auxospores described, and to follow in all their phases the curious phenomenon pointed out by him. We shall now examine the various methods of reproduction which have been described by different authors. They are four in number : — r. The reproduction takes place in a single frustule. The diatom secretes a mass of gelatinous matter with which it surrounds itself, the valves are pushed apart, the cellular contents assume a globular form and are hardened into a sporange, which itself gives birth to an auxospore. This auxospore is a body of variable form, and is enclosed in a silicious envelope ; it continues to increase and ultimately bursts the sporange and becomes free. Shortly afterwards fresh frustules, which differ slightly from ordinary frustules (particularly in their size), are observed to come into existence in the interior of this auxospore. These frustules, which are called sporangial, in their turn reproduce the primitive frustule by division. As regards this method of reproduction it is evident that authors have have either inaccurately observed or described their observations. What has been described as a method of reproduction is nothing more or less than the return to the primitive form as observed and described by Dr. Miquel. 22 THE STRUCTURE AND LIFE " I have never seen," writes this skilled observer (') " the gelatinous matter produced, nor the protoplasm form the spore any more than I have seen the protoplasm escape naked from the valves ; on the contrary I have always seen the protoplasm surrounded by an extremely thick and resisting membrane." In the following words he sums up in all its simplicity the phenomenon of the re-establishment of the form of diatoms as follows : — " The contents of the microfriistule hardens, and is surrounded by a strong membrane ; then without other visible phenomena this quasi-spore germinates and produces what is nothing less than the diatom of re-established form." Professor H. L. Smith has on his part observed the return to the sporohgial form in Cymbella euspidata, and describes and figures it (2) exactly as Dr. Miquel has done Nitzschia palea. 2. Two different frustules approach one another and pour out their cellular contents ; from this mixture is borne a single sporonge, which gives rise to the production of a sporongial frustule. Professor H. L. Smith has personally obseived this method of reproduction in Suiirella splendida. The union takes place at the narrow extremities of the two frustules, the cellular contents mix and soon there remains only an enormous sporange, which the free valves of the two original frustules enclose. The Rev. Wm. Smith has described something analogous in Himantidium, but a careful exami- nation of his plates shows that what he has seen is in reality merely the rejuvenescence or return to the maximum form without fecundation. 3. In the third method the conjugation of two frustules results in the production of two sporanges, of two auxospores, and of sporangial frustules (fig. 16). This is the most frequent and best known method of reproduction has been most carefully observed by a large number of diatomists : Smith, Pfitzer, H. L. Smith, Ad. Schmidt and myself, &c. It has been observed in Epithemia, Cocconema, Gomphonema, Encyonema, Colletonema, Navicula, &c. ( ' ) Le Diatomiste (1894) ii., p. 95. ( 2 ) Proceedings of Amer. Soc. of Microscopists, 1887. Fie. is- two It W. HISTORY OF DIATOMS. 23 4. Lastly the Rev. Wm. Smith has described a fourth method of re- production, in which a single frustule gives birth to two sporanges. This phenomenon has been recorded in Achnanthes and Rhabdonema, but as it has never been since observed it is thought that it must have been an error in observation on the part of the illustrious English diatomist. To sum up it seems probable that diatoms most frequently return to the sporangial form by an act of rejuvenescence without actual repro- duction, but that when it really does take place it is produced by the union of two frustules, which give birth sometimes to a single sporange, but generally to two sporanges. We shall here draw attention to a very remarkable idea ventilated by Dr. Ad. Schmidt. "I observed," said he, "in 187 1 the regeneration of Gomphonema mustella Ehr in thousands of cases, and what I have just said has not been invalidated by a single exception. When these Fig. 16. Fig. 16 Reproduction of I'an Heurckia rhom- boides Brcb. A. Two mother cells fusing their protoplasmic contents in order to form two sporanges. B. Two auxospores larger than the four empty valves, between which they are formed, arrived at their complete development and at the point where the terminal hoods detach them- selves to enable the sporangial frustules to pass. C. Sporangial frustules arrived at their com- plete development and still covered with the Gomphonema reproduce they have hoods which they have drawn along on leaving ... . . .... the auxospores. their stipes, and unite with their venters turned towards each other, but in an inverted position, that is to say, so that the anterior apex of one frustule rests against the posterior apex of the other." " This fact," he concluded, " in my opinion disposes of the vegetable nature of diatoms." (! ?) In concluding this section it may be noticed that, according to Kitton (') and Professor Samuel Lockwood, (2) diatoms may possess microspores so small that they can pass through filter papers. Lockwood appears to (') Kitton: On the Mysterious Appearance of a Diatom, J.Q.M.C, Ser. II., Vol. II. (1885), pp. 178-9; 206. J.R.M.S (1885), p. 1,041. ( - ) Lockwood, Prof. Samuel : Raising Diatoms in the Laboratory. Journal New York Mic. Soc. (1886) II., p. 153, two plates; J.R.M.S. (1887), p. 626. 24 STUDY OF DIATOMS. have undertaken his experiments with the most minute precautions, and the curious nature of the results which he has obtained render it advi- sable that diatomists should make fresh researches in this direction, more especially as Dr. Miquel asserts that his own experiments are not in accordance with Messrs. Lockwood and Kitton's opinions. § 2. Study of Diatoms. In my treatise on the microscope (') 1 have given all the necessary infor- mation about that instrument from the point of view of general micro- scopy. For any details which do not specially concern diatoms reference should be made to that work, and so I shall only give a few notes here specially intended to assist diatomists. Workroom. — The diatomist's workroom should not be very large ; the essential is that it should, as far as possible, be free from dust ; it will therefore be well not to encumber it with furniture or books in open shelves, but to furnish it with glazed cases, where books, instruments, and preparations may be kept. The study of diatoms sometimes requires the use of sunlight, and in that case the room should be facing east or west. Professor Harting recommends a southern situation. Although some authors condemn the latter direction, we have found it excellent, and use it almost exclusively, although we have windows with other aspects. The principal furniture of the workroom is the table. It should be heavy, massive, and of such a height as to render it possible to work conveniently when standing up. An easy position can be assumed with a high chair, but this should only be used exceptionally. In addition to the workroom, the diatomist should have a room or kind of laboratory where he can do all his dirty work, such as cleaning diatoms, boiling in acids (which latter is best effected in a glass stink- chamber, such as are used in chemical laboratories), developing photo- graphic plates, &c. Artificial Illumination. — In our climale the diatomist is frequently com- pelled to employ artificial light. Nothing surpasses incandescent electric light (-) which can be obtained at the present day in sufficient quantity for microscopical research without much trouble and at small cost. In ( ■ ) The Microscope : its Construction and Management, by Dr. Henri Van Heurck. English edition, translated by Wynne E. Baxter. London : Crosby Lockwood and Son, 1893. (2) See H. Van Heurck — L'Eclairage electrique applique' aux recherches de la micrographie, 2nd Edition in Pelletan's Journal de Micrographie ; Van Heurck's Microscope English Edition, pp. 109-117. STUDY OF DIATOMS. 25 default of this, a mineral oil lamp can be used. An excellent little lamp of this kind is supplied by Messrs. Watson and Sons for 16s. Instruments. — Microscope. — Excellent instruments are made in England, Germany, France, and the United States ; but all these instruments are not equally convenient for diatom work. An instrument will not be suitable unless it is furnished with an excellent condenser, enabling us to change from axial to ultra-oblique illumination instantly and without difficulty. We know of two condensers which perfectly fulfil these conditions, viz., Abbe's condenser and Powell and Lealand's oil condenser. The first of these apparatus is in more general use than the second, and satisfies all the requirements of the microscopist ; the second, made specially for examining diatoms, enables the diatomist to work more rapidly and with greater exactness ; the light having previously been arranged a lever has only to be pressed in order to change immediately from axial to any degree of oblique illumination. For some years Powell and Lealand have constructed an optical system, the lower lens of which has the middle part stopped, and the whole can be substituted for the ordinary optical system. It is used to obtain extreme obliquity, and is useful, for instance, for resolving the longitudinal striae of an Amphipleura. Achromatic condensers, especially for photo-micrography, are to be preferred to those that are not achromatised. Of achromatic condensers Powell and Lealand's apochromatic oil condenser is the best for resolving diatoms, on account of the largeness of its aperture, which is nearly as much as 1.4 N.A. The microscope of a diatomist who wishes to exhaustively investigate the organisms which form the subject of this work should be a first-class one ; it should be quite firm and its coarse and fine adjust- ments as perfect as possible. A sliding movement, used as a coarse adjustment, would prevent the correct centering of the condenser to be maintained ; the adjustment must therefore be effected with a rack and pinion. It is an advantage for the stage of the microscope to be fitted with a mechanical stage, by which diatoms can be easily found again and the entire preparation easily examined with the certainty that nothing has been lost sight of. The large and medium sized microscopes of Zeiss are excellent, when furnished with Abbe condensers ; but we always prefer to use the large English forms made by Ross and Powell and Lealand. The Van Heurck microscope, which is constructed by Messrs. Watson and Sons according to our specifications, realizes all that a diatomist can desire, for both the purposes of observation and photo-micrography. It is constructed 26 STUDY OF DIATOMS. Fig. 17. — The Van Heurck Microscope. STUDY OF DIATOMS. 27 either with the continental foot or a tripod ; the former is more adapted for photographing difficult objects in a nearly vertical position, the latter is more suitable and stable in the inclined position in which finished preparations have to be examined. The stereoscopic binocular microscope, almost unknown on the con- tinent and so important in histological research, is not indispensable for observing diatoms. With high powers the Wenham Prism and High-p9wer Prism are of no use, so also Abbe's stereoscopic apparatus, though fine detail can still be seen with high-power objectives, fails nevertheless to give a sharp image, which thus renders details less visible than with a monocular microscope. The ordinary binocular, giving a moderate magnification {i.e.. 200 diameters at least), is however remarkably useful for resolving the often complicated structure of Crypto-raphideas, and I venture to assert that it is impossible to form so good an idea of a diatom as when it is observed through a binocular microscope. The objectives which a diatomist requires are not numerous. Every difficulty can be met with four objectives of graduated power. In order to avoid any loss of time it is best that these objectives should be attached to a well-constructed nose-piece permanently fitted to the micro- scope. However the piece of apparatus invented by Dr. R. Zeiss called a " Sliding objective changer," is even preferable, because it enables each separate objective to be perfectly centered. The objectives which I now use for ordinary research are all apochro- matic. They are the 8mm. (r-3rd inch), 3mm. dry (i-8th inch), and 2'5mm. (i-ioth inch) N.A. 1.25 water immersion. When they are insufficient, e.g., for observing certain minute details, I have recourse to the 3-o or 2-o mm. (i-Sth or i-i2th inch) homogeneous. But these cases are rare, for they never occur when making ordinary observations for determining species, but only when elucidating structure, when all the resources of optics have to be utilised, and even Zeiss' famous objective of N.A. 1 *6 is by no means too much. Nine-tenths of the observations for determining species can be made with an 8mm. objective in combination with a series of compensating eye-pieces, particularly No. 8 and 18. We consider that this objective is the best that modern optics have produced for all kinds of ordinary work. An experienced eye can easily, with its aid, detect the bacillus tuberculosis. My work on the Microscope (x) affords all necessary information on the subject. (T) English Edition, London, 1893, pp. 101-102, 44-57, etc. 28 DRAWING AND DETERMINING THE SPECIES OF DIATOMS. Accessory Apparatus. — There is little that need be said about accessory apparatus, as it is such as is generally employed by microscopists. A heliostat is sometimes useful for observation in monochromatic light and for photo-micrography. Reference will hereafter be made to the camera lucida and also to microscopical preparations. § 3. Drawing and Determining the Species of Diatoms. A careful determination of any diatom is impossible without previously making a good drawing of it. It is only by comparing this drawing with those published by various authors that any given form can be studied. The diatomist therefore ought to have at all times the camera lucida ready at his side. I have tried every apparatus of this kind, but for working with ease I know of none which can compare with the camera lucida for an inclined microscope as constructed some years ago by Mr. A. Nachet ('). This apparatus resolves the most delicate details without any part becoming deformed, but the plane of the paper on which the drawing is made should be parallel to the surface of the prism to which the eye is applied. In drawing diatoms, hard pencils (such as Gilbert's No. 5) should be used, and they should be very finely pointed, otherwise it would be quite impossible to represent very close striae sufficiently near to one another without confusion. It is essential that all drawings should be of the same magnification, which should be sufficiently large to reproduce delicate details. All the drawings in the Atlas to my Synopsis des Diatomees de Bel^ique were drawn to 900 diameters and reduced by photography to 600. This magnification was not chosen at random. I fixed upon it in order that my drawings should bear comparison with those of previous good authors, such as William Smith, Greville, Gregory, &c, whose figures were made at 400 diameters ; mine are therefore half as large again as the figures of W. Smith and the other authors previously mentioned. It is to be regretted that Dr. Adolph Schmidt has used so arbitrary a magnification as 660 for his Diatom Atlas. In the present state of the science a magnification of 400 diameters is no longer sufficient for an original drawing, and as far as possible all drawings should be 900 diameters, while certain details even require double that amplification. In the present work the drawings of Genera have been made at 900 diameters, and wherever possible have been reduced to 600. With regard (') The Microscope: English Edition, London, 1893, pp. 92-93. COLLECTIXO DIATOMS. 20 to the drawing of Species the original designs have in the same way been made at 900 diameters, and have been reduced by phototype to 400 diameters in order to diminish the expense and so render the work available for a very large number of observers. The figures of this work will therefore often be improved by the use of a magnifying glass. § 4. Collecting Diatoms. A. — Collecting Inland. Diatoms are to be found distributed everywhere ; whatever water- course may be explored our researches are almost certain to be rewarded ; the smallest ditch, the smallest pool, provided the water is not stagnant, contains diatoms in greater or less numbers. Moreover they accumulate in prodigious manner. It is by reason of this fact that at different times I have found the bottom of the immense harbour basin of Blankenberge entirely covered over with a thick deposit of diatoms, principally consisting of Pleurosigvui. When starting in search of diatoms, certain necessary collecting instru- ments and appropriate vessels to contain the gatherings must naturally be got ready. The following is a list of the articles which a diatomist may take with advantage on his excursions : — The principal article is a leather bag fitted with a strap; this is carried over the shoulder and under the arm. The bag should con- tain a sufficient number of pockets to carry a dozen wide necked bottles of say 20Z. capacity, a smaller leather case containing six large phials with wide necks, holding about 1 oz. a piece, each phial fitting into a pocket ; in the country this case is carried in the pocket of the overcoat. Next comes a box containing some small tubes and a camel's hair pencil for painting off pure gatherings, or avoiding the inconvenience of bringing home a larger quantity of material. In addition to the bottles and the tubes, some pieces of gutta-percha paper or waterproof macintosh cloth, nine inches square, are very useful to wrap up algae, masses of confervae, and other diatom-yielding plants ; these are made up into bundles, after slightly pressing out part of the water. These bundles are kept from unfolding by an elastic ring, and are put at once into the bag. For scraping the surface of mud, such as alluvia, the sides of jetties, &c, the writer uses a copper spoon with a screw clamp to fasten to the end of a walking-stick when used. On one side of the neck of the spoon is rivetted a small knife blade, which forms a convenient means of cutting away portions of aquatic plants covered with diatoms and lifting them out of the water. 30 COLLECTING DIATOMS. The only lens necessary to a diatomist when out collecting is a Coddington, but the writer has found a small compound hand micro- scope very useful occasionally. This, with some slips of glass, are carried in a separate compartment in the leather sachel. For some time past we have used with advantage a small pocket microscope, sold by E. Thum, of Leipzig, and which he has named an Algensucher. This instrument is in the form of a tube, 5 or 6 centimetres (2 inches) in length by 3 centimetres broad. This tube carries at the upper end the magnifying apparatus, which consists of a doublet, under which can be placed two glass slips sliding in a groove and held in position by a spiral spring. The diatoms are placed on one of the slips and can be covered over by the other. This little apparatus, which is very convenient, can be furnished with interchangeable doublets, so as to give different magnifications varying from 50 to 200 diameters. Now that we are equipped and ready to start, the question arises, where shall we go in search of diatoms ? In 1872 there was published in the Lens of Chicago (') an article copied from the Intellecttial Observer, (2) entitled " Where to search for Diatoms." This article gives very valuable information to the young diatomist, and we believe that we cannot do better than reproduce the greater part of it :— " A knowledge of the most likely places to look for Diatomaceas is only to be gained after some experience, and it is the wish of the writer to give the result of his experience in the matter, which has induced him to pen these lines. In mentioning the various species of Diatomaceas in connection with given habitats and localities, it may be as well to say that the writer has, in most cases, found the species named in such localities ; not necessarily in one particular district, but at various times and in different parts of the country. " We will now suppose the collectors are commencing their imaginary collecting tour, and, before leaving the town, let us take a stroll round the docks, for here we may meet with material in places where such might be the least expected. For instance, let us examine the logs of Baltic or American timber as they come from the vessels. If the (V) The Lens (1872), i., pp. 106-116. ( 2) Intellectual Observer (1872), i., pp. 190-199. COLLECTING DIATOMS. 3 1 timber has remained for any length of time afloat before shipping, the logs are almost sure to have traces of Confervas, either fresh water or marine, growing on them, and these, on being carefully scraped off, will, in all probability, yield diatoms to reward the collector. Some of the logs from the St. Lawrence or the Ottawa will yield us American forms, while logs from Dantzig will give us interesting gatherings from the Vistula and the interior of Poland. "Should a vessel be unloading " Kaurie spars" from New Zealand, or some of those gigantic " sticks " which have lately been imported from Vancouver's Island, we may probably be rewarded by finding beautiful Antipodean forms of Diatomaceae on the former, and the exquisite Arachnoidiscus or Triceratiuin IViikesii from the latter — perhaps even Aulacodiscus Oregonus. " Let us not go past these mahogany logs landing from Mexico or Honduras, as the case may be, without casting an eye over them, for these may have been rafted for some time in the sea before ship- ment, or may have brought down new or little known forms from the interior of Central America. Here, on the first log we examine, is a copious incrustation of a form either identical with or closely allied to Melosira nummuloides, abundant likewise in our docks. The gathering is so copious that it fairly glistens in the sun. "Let us also scrape away some of the shelly incrustation of Ba/anus, which completely covers some of the logs, for possibly among this we may find that exquisite American form Terpsinoe musiea, so called, I suppose, from the costal appearing like so many musical notes. " Here are some fishermen just coming in. Let us examine their nets, for these men are trawlers, and have been fishing in deep water, and the meshes of their nets may still have diatom-bearing Algae attached to them. On such Algae we may probably find Rhabdonema arcuamm or Adriaticum, Grammatophora serpentina and marina, with species of parasitic Synedras ; possibly the singular Synedra undulata may reward our search. " Some of the oyster shells from deep water are worth examin- ing for marine Algae, or, what is even better, the greenish, leathery- looking ascidians attached to them. The ascidians are regular feeders on diatoms, and their stomach contents often yield a rich harvest of deep-water forms difficult to obtain in any other way. Perhaps we may be securing the rare Biddulphia regina, at any rate Biddulphia Baileyii and aurita. We will take some for future examination, for the curious Rhizosolenia styliformis is almost sure to be there. 32 COLLECTING DIATOMS. " Let us step into a boat and examine that ship's bottom and sides, which look so brown with a growth of conferva and barnacles. Here the spoon becomes of use. Scrape very gently where the deposit is the darkest in color, and let us see what we have got — Achnanthes longipes and brevipes in abundance. These are common enough elsewhere in the timber ponds, so we will only secure the little thing in zigzag filaments, for this is probably Diatoma hyaltnum, or, perhaps, the rare Hyalosira delicatula. "Is it not singular that such delicate filaments, hanging together by the angles of the frustules, should be able to withstand the rushing of the vessel through the water during the long voyage she has just com- pleted ? " The ballast-heap must not be passed without examining. Here are stones densely covered with marine Algae and Corallines, which we will scrape off and store away for after-examination. Biddulphia pulche/la, Aniphitetras, Grammatophara serpentina, or possibly some of the beautiful foreign species of Aulacodiscus, may reward our trouble, for this ballast is brought from all parts of the world. The only matter of regret is the difficulty in ascertaining the exact localities. " Let us now take some of the Zostera which is being landed on the quay in large bales ; it is extensively imported from the Baltic as Ulva marina, for stuffing chairs and mattresses. Cocconeis scutettum and diaphana, with Epilhemia and a medley of other forms, are generally found parasitic on the Zostera, and may be easily separated by macera- tion in weak acid. " But what are those brown bundles landing from the steamer? These are " Dutch rushes," for coopers' purposes and chair-bottoms, and are well worth examining, for, growing as they do in brackish water in Holland, the sheath at the base is often completely coated with diatoms, Coscinodiscus subtilis, for instance, with other good things, such as Enpodiscus argus and Triceratium favus. '• Nor must we pass these cargoes of bones discharging into lighters. See, some of the larger bones have evidently been lying in the water some time, for they are covered with a green incrustation. Let us scrape away the incrustation, for we may find among it the fine Synedra crystallina or undulata, together with valves of Coscinodiscus and Eupodiscus. Many good gatherings have been procured from this source, especially from cargoes coming from Constantinople, Smyrna, and the Black Sea. "Ask this sailor if he has any foreign shells still in the rough state; if he has any for sale, they are certainly worth securing for the small COLLECTING DIATOMS. 33 Algse and Corallines found growing on them. These, on being cleaned, often yield splendid results. Many of the most beautiful and rare species of Campylodiscus have been obtained from this source. The Californian Haliotus shell is almost certain to yield the fine Aulacodiscus Oregonus, Arachnoidiscus, Hyalodiscus cervinus, and Biddulphia Roper i; while the Haliotus from New Zealand will probably furnish the rare Aulacodiscus Beeverice and Macraeatius. " The West Indian Strombus shells invariably yield beautiful forms, such as Campylodiscus eccltsianus, ambiguus and imperialis. " Vessels with guano are worth visiting. The Peruvian guano, when properly prepared, yields the magnificent Astcrolampras and Aulacodiscus scaber ; while the Bolivian is even richer in fine things, such as the superb Aulacodiscus formosus and Comberi. Californian guano yields, among an infinite variety of forms, many of great beauty and rarity, such as Aulacodiscus margaritaceus and Biddulphia Tuomeyii. Algoa Bay is frequently rich in Aulacodiscus Petersii ' ; and finally, the Ichaboe guano, Eupodiscus Ehrenbergii, and other good things. " The old mooring anchors and cables, which are now lying on the quay, are covered with a marine incrustation, which, on examination, will be found deserving of notice. "We will now take a stroll towards the timber ponds, where the timber often remains afloat for years. Here we see ample traces of the objects of our search. The sides of the logs seem quite covered with a tangled mass of the filamentous forms ; but before we bottle up any of them, let us collect with the spoon some of the brown pellicle which covers the surface of the water. This proves to be a very pure gathering of Amphiprora constrida. Then let us collect some of the green Ulva and Enteromorpha, growing on the sides of the timber, which seems so brown and furry. With the Coddington lens we find the brown tint is owing to a dense parasitic growth of Achnanthes longipes and brcvipes. The long brown filaments are principally Melosira nummuloides and Borren'i, with Schizonema crucigerum and Dillwynii, mixed with Bacillaria paradoxa, shooting into long filaments, then suddenly retreating until the filament is closed again, one frustule sliding past the other in a most marvellous manner. By the way, this species will live, and even thrive, quite well in perfectly fresh water. Mixed with the Bacillaria, we find Nitzschia Sigma, and other free forms. "The wooden piers running out into the river are brown, with a covering of Homceocladia siqmcidia, Pinnularia /o/insonii, and Navicula D . :\ R ' 34 COLLECTING DIATOMS. ellipsis. On another wooden breakwater we find Pleurosigma scalprum and Navicula mutica. " Leaving the immediate vicinity of the docks, we come to a maze of ditches, to which the salt water has access during spring tides, and these ditches are often very rich in Diatomaceag. Let us commence operations here by collecting this brown covering from the mud. Here we have Pleurosigma angulation, fasciola, Slrigilis, Hippocampus, Nitzschia sigma, and Surirella gemma. Such gatherings may afterwards be entirely cleaned from the mud by covering the outside of the bottle with black cloth, and letting it stand for some days in the sun. The diatoms by this time will have worked themselves to the surface, and the thick brown layer will be found quite free from impurities. This plan, if carefully carried out, rarely fails. The brown floating scum must by no means be neglected, for on bottling some we find we have secured a good gathering of Pleurosigma fasciola, macrum, and delicatulum, with, perhaps, Navicula ambigua, and other good things. " Proceeding to another ditch, we will take a dip from the mass of brownish stuff which coats the weeds. Well, here indeed is a capital haul, for we have Nitschia bilobata, Brebissonii, vivax, with Tryblionella gracilis, Navicula a/nphisbcena, Pinnularia peregrina, and Cyprinus. " Further on we pull out some of the weeds which are covered with brown furriness, and we have a gathering of Synedra fulgens and Amphipleura Danica ; while on the mud we obtain a copious one of Stauroneis salvia, Nitzschia dubia /3, with Navicula minulula. "But what can this brown hairlike mass be, growing parasitically on the reeds and floating pieces of stick? On examination it will prove to be pure Melosira Borrerii, which we will bottle up with great satisfaction. " Further on we come to a large lagoon, and find therein some plants very promising in appearance, and well worth gathering. These yield us afterwards a fine mass of Amphiprora alata and paludosa, Pleurosigma strigilis, Amphora salina with Surirella Brighttvellii. " Mind how you step over this boggy ground, with the ink-black mud, smelling so unpleasantly of sulphuretted hydrogen. In spite of the smell, we shall probably get something to reward us. Collect carefully the brown covering from the mud, and you may find Navicula elegans, lumens, Nitzschia dubia, Epithemia musculus, Amphora affinis, with Pinnularia Cyprinus and peregrina. " We now approach the banks of a canal, into which the brackish water sometimes gains access. Let us hook out some of the COLLECTING DIATOMS. 35 Potamogeton and other weeds. Well done ! we have here something that will reward us for our fatigue. Examine it with the Coddington ; the circular discs are valves of the rare Cydotella punctata. Mixed with these we find Campylodiscus cribrosus, Bacillaria paradoxa, with a host of other both fresh and salt-water forms. " With the tweezers let us now carefully pull off some of the brown tufts growing on the clay banks of the river. This looks like some stunted Conferva. On examination with the lens, the filaments are found crowded with rows of little sigmoid things, for all the world like miniature specimens of Pleurosigma Balticum. This is a prize again, being no other than the rare Colletonema cximium. " Leaving this locality, let us proceed a few miles down the river towards its embouchure, and where the water is Salter. Being low tide, we see for miles the mud is colored of a dark chocolate-brown tint, owing to the presence of millions of Naviada Je?inerii. In the large lagoon formed by the salt water getting over the embankment during spring tides, we shall probably find an abundance of good things ; among these many of the filamentous Schizonemas, Rhipidiphoras, and Podosphenias, and even Lianophora flabellata. Proceeding even further down the river, the mud gradually disappears, sand takes its place, and afterwards we come to the open sea where the coast is in places guarded by rocks. Here is a fine field for the purely marine forms. Let us gather some of the wiry green tufts of CladopJiora rupestris, one of the best of the diatom-bearing Alga?. The tips of the CladopJiora are quite brown with a parasitic growth of Grammatophora marina and macilenta, together with Rhabdonema arcuatum, Cocconeis scutellum, and Gomphonema marina. On the other Algae, growing among the rocks, we find masses of Podosp/ienia, and perhaps the easily-overlooked Hyalo- sira delicatula. The brown hairlike mass floating about, but attached to the stones, is Fragilaria striatuJa, and some of the filamentous Schizo- nemas. " In the rocky pools left by the tide are some masses of Coralina officinalis, growing in dense tufts. This Alga is an excellent diatom-trap, collecting the floating frustules among its tangled branches. We must, therefore, select a good stock of the Coralline, lifting it out of the water with as little violence as possible, for fear of washing off the diatoms. " Washing afterwards in acidulated water will liberate the frustules, and then we have probably a fine gathering of the beautiful Eupodiscus Ralfsii, with Eupodiscus subiilis ; perhaps also Amphiprora lepidoptera, and other nood forms. 36 COLLECTING DIATOMS. " The sand in sheltered places, you will observe, is brown in the hollows of the ripple-marks. This is caused by millions of diatomaceous frustules, and we must by all means take home a good store of the brown sand, which by washing easily yields up its riches. " Having spent so much time on the marine and brackish-water gatherings, let us turn inland and proceed where the tide ceases to have any influence. To make sure of this, we will take the rails and go to the rocky hills some ten miles distant. Having arrived there, let us examine, in the first place, this rocky streamlet, for I see traces of a brownish covering on the stones, and also some pretty long streamers. Lift the filaments out gently, or you will get little into the bottle. On examination at home you will probably detect Odontidium mesodon, Himantidium undulatum and Anus, with Tabellaria fenestrata and flocculosa. " Proceeding a little further, we come to a little water-fall trickling down the surface of the rock and gradually finding its way to the stream. The brown, velvety covering on the stones looks very promising for our purpose, and, if I mistake not, we shall be well rewarded for our trouble in carefully collecting a bottleful of the material, for we have a good gathering of the beautiful Gomphonema geminatum and ventrico- sum mixed with the minute Acnanthidium linearc. The brown mass completely covering the stones in the bed of the stream is Coaonema lanceolatum, not often found so pure. "Let us see what causes the green colour on the surface of the mud in the roadside puddle. Ah, this is indeed a treasure ! for it is seldom that Navicula cuspidata occurs as perfectly free from mixtures. The green colour is also remarkable, being so different from the usual brown endochrome of most diatoms. "Here is another roadside puddle left by the recent rain; and see what a brown coating has grown at the bottom in so short a time. At any rate, we have here Diawmacece in abundance, though small in size, probably Nitzschia palea and Pinnularia pygmcea. "Proceeding further inland, we are supposed to be passing a water- mill ; and, as the mill-race is covered with confervoid growths, let us examine some of the coating from the wooden aqueduct. The brown streamers are in all probability Diatoma vulgare and elongatum, and the beautiful stellate form is the local Asterionclla formosa, which, by the way, seems to select its habitat always in some out-of-the-way place> such as the present one in the mill aqueduct, water tanks and reservoirs. " Having climbed up some distance on the hillsides, let us collect some of the weeds from the sides of the boggy pool, for in such COLLECTING DIATOMS. 37 localities we may expect to find some of the rarer alpine forms, Navi- cula rhomboides, obtusa, Pinnularia divergens, lata, and Alpina, for instance. The pale-green flocculent mass growing in quantities like a conferva is well worth collecting, for it is a pure gathering of Tabellaria ftocculosa and jenestrata. " In tramping over this quaking bog, it is well to roll up a bundle of the Sphagnum, for on afterwards squeezing out the water we may be rewarded by finding some of the rarer species of Pinnularia such as hemiptera and Alpina. " Before leaving this rocky part of the country for the flat country below, let us scrape some of the brown mucus from the face of the dripping rocks, for it will probably yield such forms as Epithemia, Cocconeis Thwaitsii, Navicula truudis, Denticula sinuata, &c. "The weather being warm, we will quench our thirst at the little spring in the cavern-like hollow in the rocky roadside. Observe, the roof of the little cavern is quite covered with a chocolate-brown mass, which feels rough and gritty to the fingers. Here is a splendid and pure gathering of Orthosira arenaria, and I recommend you to take a good store of it away with you, for it is seldom one finds this fine form so pure and unmixed. " Proceeding towards the low country, let us take a scrape from the side of this horse-trough, for it is quite brown. It is well we have done so, for it is a nice pure gathering of Cyclotella operculata and Pinnularia pygmaa. " Passing a little further on, we come to a clump of ash trees, with a crop of moss growing on their trunks. Perhaps you may smile when I proceed to peel off this moss and store it away in a bundle in my satchel. On washing the moss afterwards, however, I may be rewarded with some of our most local and rare species, viz., Orthosira mirabilis, mixed with Navicula tumida, Pinnularia borealis, and Ortho- sira spinosa. "Having secured a bundle of moss from the tree-trunks, we will take another from the roof of this old thatched cottage, the north side of which is quite carpeted with beautilul green moss. This will pro- bably yield Nitzschia Amphioxys and Pinnularia borealis. " The white-colored stratum of earth exposed in the cutting on the roadside must now be examined, for it is probably a deposit of fossil diatomaceous earth ; in which case a large piece must be secured. "These fossil deposits are generally composed of a compact mass of Diatomaceae of recent as well as extinct species. The deposit we are 38 COLLECTING DIATOMS. at present examining is several feet thick, and has at some remote period formed the bed of a lake, the diatoms accumulating at the bottom until the present thickness was attained. You will observe that the endochrome has been removed by long rotting, and the entire mass is now composed of the pure white siliceous valves. Pray also observe that this richness in silex suits the cereal crops growing over it, but does not seem to furnish much nutriment to the potatoes and turnips. " The adjacent peat-beds may also be examined, for frequently rare Diatomacea^ are found in the turf which is cut for fuel. "The dark, hairlike mass growing on the wood-work of this sluice- gate is a nice pure gathering of Schizonema neglectum, the frustules arranged in regular rows in the interior of the long filaments. " Before leaving this pond, let us pull out a mass of the Myrio- phyllum, which seems rusty in color. Well ! here is a medley of forms, but the gathering is worth bottling up, owing to the abundance of Amphipleura pellucida. " The clear ditch by the roadside is a likely place for such forms as Pleurosigma attenuation, Spencerii, and lacustre, Nitzschia linearis and tenuis, Surirella ovata, Navicula elliplica and Cymbeila maculata. " The yellow mass attached to plants a little further on is Cydotella operculata, Amphora ovalis, and Nitzschia sigmoidea, while the brown covering on the Anacharis is GompJionema tenellum, dichotomum, and curvaium. The stones in the running beck, issuing from the clear spring close by, are covered with long, yellowish-brown streamers, which are well worth collecting. Take them out very gently, for they are very fragile, and likely to drop again into the water. The species is the beautiful Meridion circulare, with Melosira varians. At the bubbling spring itself, which forms the head of the streamlet, the sand, which is tossed and heaved about by the ascending water, seems tinted of a brown color. Let us secure some of the sand, when we shall find the brown color is caused by a dense parasitic growth of Odoniidium Harrisonii quite pure. " Farther on the dark brown streamers must be collected, for here are two species of Fragilaria, capueina and virescens mixed with Dia- toma elongatum. The stones and aquatic plants are likewise covered with a dense brown coating of Synedra radians and ulna, species found in almost every clear water ditch. " The boggy place where the plants are coated with a yellow coat- ing of the oxide of iron, is not to be passed without collecting a little COLLECTING DIATOMS. 39 of this light flocculent surface mud. This will be almost sure to 3 ield some fine diatoms, such as Campylodiscus spiralis, Pinnularia nobilis Stanroneis Phcenicenteron, Surirella splendida, and Cymatopleura solea. " Here we must finish our day's work, having arrived at the railway station, from whence we proceed home with our treasures. The work of collecting has been finished, yet much remains to be done before the material is cleansed and mounted on slides for microscopical investigation. " Let us hope our fatigue has not been in vain, but that the store of riches we have collected together will furnish us with ample material for much interesting study and instruction." B. — Marine and Pelagic Collections. To obtain an exhaustive knowledge of diatoms, it will not be sufficient to study those forms only which are met with in streams, on the banks of rivers, and on the sea shore, for in that case our knowledge of them would be very incomplete indeed ; but we must also examine all fossil deposits as well as marine and pelagic diatoms. It is in fact, just as important to obtain forms which are found at the bottom of the sea as those which float just under water or on the surface of the ocean and the mouths of large rivers. It is only of late years that it has been discovered how numerous are these floating forms to which the name Pelagic diatoms (x) has been given, and how much they vary according to the seasons and under the influence of currents and other causes which have not yet been completely ascertained. For the last eight years I have specially devoted myself to the study of marine and pelagic forms, and have made hundreds of gatherings of them, and for this purpose I have used my steam yachts " Nautilus " and " Suzon." The former is specially constructed for exploring the upper Scheldt ; it is a flat-bottomed paddle-boat, and by reason of its small draught and the special form of its keel it can navigate shallow water with impunity. I have used this yacht most frequently in making gatherings in the upper Scheldt between Ghent and Saftingen, while the "Suzon" (2) has been used for the lower part of the river and the North Sea. ( « ) It would be better to describe these diatoms as Floating, or Wandering. The Germans use the word " Plankton " (from -rrXayKrog — wandering, roaming) to denote all living organisms which are displaced in this way under the influence of currents, &c. (") The "Suzon" comes from the shipyard of Messrs. Watkins and Co., of London, who are considered among the most skilful yacht-builders in England. The " Suzon " is con- structed entirely of teak wood, having a draught of 6ft. Its length is 60ft. , and breadth njft. Being very narrow and fitted with powerful machinery it can, when running with the tide, make nearly n knots, and can carry coal to last eight days. 40 COLLECTING DIATOMS. Special apparatus is required for collecting marine and pelagic forms. My own is very simple, but in spite of its extreme simplicity it has, nevertheless, proved hitherto sufficient in all my expeditions, and I do not think that anything further is necessary. My apparatus consists essentially of a grapnel hook and a series of nets (Frontispiece, figs. A — E). The hook has three barbed ends, and is attached to a long cord. This is used to secure or draw in any alga? which may be seen floating about, or which may be found on the banks of rivers or shallow bottoms. It is also trailed behind the boat, and so drags along the algoe and other bodies which it happens to catch hold of at the bottom of the sea or river. The nets are of four kinds : — i. A bottom net or drag (Frontispiece, fig. B). — The net is attached to a heavy ring of tinned iron ; its weight is sufficient to make it scrape the bottom, so that it collects the sand and other bodies over which it trails. 2. A subsurface net (Frontispiece, fig. C). — In this the ring of tinned iron is rather lighter, and is, moreover, sustained by a piece of cork on either side; the whole is balanced so as to be suspended at about ift. to 2 ft. below the surface of the water. 3. A surface net (Frontispiece, fig. D). — The upper end of the net consists of a wooden frame of square section, which is very long. This frame as it is drawn along by the launch floats just at the surface, so as to collect any diatoms which may happen to be there. This kind of net, as a rule, gathers the most interesting kinds of diatoms. To the framework of each of these nets is attached a cylindrical bag made of very stout cloth, to which again is attached the real net, which should be made of silk gauze of the best quality, such as is used for making fine silk strainers. 4. An ordinary fishing net. — This net is square and rather large, with fairly close meshes, and is useful for collecting alga? and shells at the bottom of the sea, which are so frequently covered with interesting diatoms. All the nets, except the surface one, should have long stout cords attached to them, so that they may work well and overcome a fair amount of resistance. It need scarcely be pointed out that all gatherings should be made against the current, and with the engines eased down to the minimum, i.e., so as only just to counteract the current and so remain stationary, or, COLLECTING DIATOMS. 4 1 at all events, only make the slightest headway. Any attempt to go quicker is useless, for it will be quite impossible to obtain gatherings, owing to the fact that there would not be time for the water to filter through the net, and there is also a risk of tearing or even of altogether losing the net by the cords getting broken. From time to time the nets are drawn in on to the deck of the vessel, and are carefully washed in a pail of water, which is left standing for a considerable time. After decanting the supernatant liquid, the sediment in the bucket is put into bottles, which are then carefully labelled, to avoid any subsequent confusion. From pelagic gatherings many very rare forms may often be obtained in great abundance which are only met with exceptionally in shore mud. The following is a list of diatoms found in a pelagic gathering made at Hansweert, a maritime partion of the Scheldt, about 31 miles from Antwerp, on the 22nd May, 1892 : — Rhizosolenia setigera. „ Shrubsolii. Plagiogramma Van Heurckii. Synedra nitzschioides. Eucampia Zodiacus. Chsetoceros Wighamii. Ditylum Brightwellii. Biddulphia Isevis. Coscinodiscus Oculus Iridis. „ concinnus. Lithodesmium undulatum. Actinoptychus (Secondary valve = Debya insignis). Triceratium Favus. Campylosira cymbelliformis. Skeletonema (Melosira) costatum (Grev.), Grun. Up to the present time we have only incomplete data as to the origin, the rapidity of propagation, and the direction which these masses of float- ing diatoms take on our coasts. It will depend upon the littoral currents, of which we have no information, and on the sea currents which give rise to the "flow"('), a current which sets out from the English Channel coast along the Belgian shore, bearing E.N.E. to N.E., and the ebb tide (reflux or descending sea), which comes down from N.N.E., and takes a (r) Etude sur les courants de la Mer du Nord par. M. Petit, Directeur du service de 1 hydrographie de Belgique. Anvers. Tessaro. 1892. 42 COLLECTING DIATOMS. S.W.iW. or S.S.W.|W. direction, and which is in part dependent on the sea wave coming from the north, and in part on waters of the English Channel returning again. (') The pelagic gathering mentioned above, made during the flowing tide, also shows its southern origin by the diatoms of which it is composed. C. — Collecting from Fossil Deposits. Fossil deposits may be divided into marine and fluvial deposits. Marine deposits. — " Gather all earths," writes our friend Dr. Arthur M. Edwards, "of light colour, varying from a pure white, through different shades of grey, cream, and fawn to an iron-rust tint. The texture is often friable, and then looks somewhat like clay, especially when it is wet ; at other times it is of a hard and stony character, although always more or less porous, and when soft, of little weight. Collect enough to make up three or four pounds weight, or, say, a block six or eight inches square, and, if possible, at various depths, because often these deposits vary in character according to the depths at which the gatherings are made. Every- thing that can be ascertained with regard to their position and their relation to other beds should be noted. Also any fossils contained in them or in the strata above or below them ; if they are not known they should be taken in order to fix their species later. All specimens should be kept carefully separate (not even permitting them to come in contact) by wrapping each one in paper, placing within a label having written upon it in ink the exact locality, date of collection, and name of collector. It is also desirable that note should be made of the depth from the surface at which the specimen was taken, together with any other infor- mation that may be deemed of interest, as supposed extent of stratum, slope-upwards towards north, south, east, or west, and thickness." Guanos. — In conjunction with marine diatoms we ought here to mention guanos which (as is well known) consist of the excrements of web- footed birds found in warm regions of the globe, especially Peru, the Chincha Island, Bolivia, &c. The birds which produce guano feed on fish and various marine products, all of which contain diatoms or have them on their surface, and consequently diatoms may often be found in these guanos in large quantities ; by properly treating such guanos, many rare forms can be obtained, which would elsewhere be sought for in vain. Unfortunately, the best guano deposits are rare, or becoming so, and commercial guanos are so often adulterated. (') Petit, op. cit., p. 54. CULTIVATION OF DIATOMS. 43 Lacustrine Deposits. — These deposits are produced in lakes, ponds, and rivers. Strictly speaking, they are not fossils but rather recent deposits, since the greater part of the diatom forms contained in them are identical with living species. They, however, sometimes belong to the tertiary and also quaternary periods. These deposits are pulverulent, and when dry they are remarkably light. They are either quite white or grey, according to the quantity of organic matter which they contain, and have been said to resemble powdered starch. Their dampness when fresh usually deepens their colour which becomes lighter as they dry. These should be gathered in exactly the same way as marine deposits. As these beds are seldom of any great extent (they often become soon obliterated or covered up) it will be well to secure a good supply of the material whenever the opportunity presents itself. If any shell, wood, or other organic remains be found dispersed through the deposit, or overlying or beneath it, they should also be collected, and their position recorded on the label. Deposits of fossil diatoms are numerous, and are found in very various localities. The most ancient is that found in 1878 by Mr. Shrubsole, of Sheerness-on-Sea, in the London clay, which belongs to the Lower Eocene (Tertiary period). Some of the diatoms found by Mr. Shrubsole are encrusted with pyrites, and some have even been transformed into pyrites. The number of species found is rather large, the most common being Coscinodiscus perforatus (?) and Coscinodiscus minor. (?) (') § 5. Cultivation of Diatoms. Every diatomist has at some time or another made diatom cultiva- tions, that is to say, has tried to keep alive the species which he has collected on his excursions, or which may have been accidentally developed in the jars or aquariums of his laboratory. But the attempt to keep any species alive for a protracted period rarely succeeds, and then only under certain circumstances, which cannot be fully ascertained. The longest cultivation, we believe, which has hitherto succeeded is one which we have in our own laboratory, dating back to 1886, since which time some Navicula didyma and Amphora duplex have continued to multiply. (J)The Diatoms of the London clay, by W. H. Shrubsole, F.G.S., with a list of species and remarks by F. Kitton, Hon. F.R.M.S., J.R.M.S. (1881), p. 381. 44 CULTIVATION OF DIATOMS. Dr. Macchiati published a note ( ' ) on the cultivation of diatoms on the 22nd March, 1892, but this little work only contained theoretical data, and gave no precise directions which couid guide the worker. On the other hand, Dr. P. Miquel, whose papers on the repro- duction of the sporangial form have been previously mentioned, has published in Le Diatomiste and in the Amiales de Micrographie, a series of articles in which all the questions relating to the cultivation of diatoms are examined in detail. The manuscript of the former of his articles was sent to Le Dialomiste on the 30th January, 1892. The French observer may therefore just claim priority in producing artificial cultivations of diatoms, which are destined to play so important a part in the iuture study of diatoms. Dr. Miquel has laid before the Academy of Paris a paper in which he lays down general directions for cultivating diatoms (2). We shall now proceed to reproduce this paper, and then make a summary of the various publications by Dr. Miquel, on the subject under consideration : — ■ "The silicious phaeophyceae of the family of Diatomacese," says Dr. Miquel, "which hitherto have never been artificially cultivated, can nevertheless be cultivated in laboratories just like other microscopical plants. "From a careful chemical analysis of the fluid media, in which these algae are usually found growing in nature, I have drawn up a few instructions which have been invaluable in enabling me to ascertain the composition of the nutritive macerations which favour the multi- plication of diatoms. " Ordinary water when placed in glass jars, containing pieces of stalks of grass, husks of wheat, barley, oats, &c, and fragments of mosses, is rendered very favourable to the reproduction and multiplication of fresh water diatoms. The excrement of rodents and ruminants may also be used for the same purpose, but the latter are more inclined to favour the development of Chlorophycege than of Phaeophyceae. Fleshy muscle, washed and cooked, may also be used to charge the macera- tions with organic matter, but with much less success. The effect of adding to the cultivating media, soluble hydrates of carbon, albuminoid substances, white of egg, blood serum, gums, gelatines, &c, is either negative or else harmful, since a certain number of fungi are sown with the diatoms. ( * ) Dr. L. Macchiati : Communicazione preventiva sulla cultura della Diatomee. Extratto dagli atti della Societa dei naturisti di Modena. Ser. III., Vol. XL, 1892. (a) De la culture artificielle des Diatom^es par M. P. Miquel, 28th March, 1892. CULTIVATION OF DIATOMS. 45 "Among the mineral elements whose fecundating action on diatoms is very remarkable, I shall quote the following salts of sodium, potassium, and calcium, viz. : — the chlorides, bromides, iodide, phosphates, and sulphates (i to 5 parts dissolved in 1,000 parts of water, or more concentrated for certain frustular species). Sodium silicate (t in 1,000) would seem to have no effect on these alga?, as they appear to more easily assimilate the silica, contained in vegetable matter and liberated by slow and progressive decomposition, than that of the silica contained in soluble chemical combinations. Lastly, a compara- tively weak solution of the salts of ammonium, particularly the nitrate, impedes the growth of diatoms, but the phosphate of ammonium is an exception and favours it. "There is no greater difficulty in producing cultivation of marine than of fresh water diatoms. Artificial salt water which has been obtained by adding to every litre of ordinary water 25 grammes of sodium chloride, 1 gr. of magnesium sulphate, 5 gr. of calcium chloride, and -i to -2 gr. of potassium or sodium, bromide and iodide produces a mineral medium which is found to be very suited to the cultivation of marine Algae, if a few straws and some fragments of Fucus and wrack be added. " To obtain absolutely pure cultivations of diatoms the maceration should be prepared without applying heat 8 to 15 days before using and filtered with a Pasteur-Chamberland filter before planting. " In the case of ordinary cultivations the planting may be done at once, but the entire maceration must have been previously sterilised at a tempera- ture of 7o°c, at which almost all microphytes except Bacteria are destroyed. " Diatoms introduced into these various media produce at the end of eight days healthy cultivations consisting of magnificent deposits of a colour varying from golden yellow to dark brownish red and formed almost exclusively of the planted species. " By varying the mineral and organic composition of these media, by increasing or diminishing their nutritive power any particular species can be made to predominate. As diatoms are unequally affected by heat and the toxic qualities of antisceptics it is easy by means of this physical and these chemical agents to separate the Algae from one another by making use of a system of diluting. "As diatoms cannot withstand the heat of direct solar rays, diatom- cultivations should be placed in a northern aspect either in the open air or behind windows of transparent glass. The light diffused from the sky is always sufficiently powerful to ensure the development of diatoms. Inside poorly-lighted rooms the cultivations are arrested ; but 46 CULTIVATION OF DIATOMS. even then three months after planting, these still unfertilised cultivations need only be exposed to the full light of day to spring into visible activity and to become a flourishing colony. From o° (c.) to io° (c.) the diatoms show perceptible signs of multiplying; from 50 to io° the cultivations proceed slowly ; from io° to 200 they become luxuriant ; and then at 45 ° the diatoms are utterly destroyed. " Diatoms can be cultivated in a volume of liquid varying from several litres down to 1 c.c. or 2 c.c. ; I have made use of this property to follow the development of these Algae under the microscope and to witness various phases of their generation and multiplication which I shall describe in a future note." Dr. Miquel draws a distinction between Ordinary Cultivations in which one or more species are cultivated together lor the purpose of having them constantly at his disposal for any kind of research and Pure Cultivations where a single species is made to pass through all the phases of its existence in order to follow every modification which it would spontaneously undergo, or which can be artificially produced or again in order to cultivate them in such a manner as to be able to make a number of durable microscopical preparations. The cultivations are again divided into Cultivations of Fresh Water Diatoms and Cultivations of Marine Diatoms. Formula for Solution A. A. — Ordinary Cultivations of Fresh Water Diatoms. Diatoms are cultivated in water containing saline and organic nutriments. The saline nutriments are prepared in two solutions, A and B. Formula for Solution B W Sodium Phosphate ... ... 4 gr. Calcium Chloride (dry) ... 4 „ Pure Hydrochloric acid at 220 (c) ... 2 c.c. Hydrous Ferric Chloride at 45° (c) 2 » Water 80 „ Magnesium Sulphate Sodium Chloride ... Sodium Sulphate ... Ammonium Nitrate Potassium Nitrate Sodium Nitrate Potassium Bromide Potassium Iodide ... Water 10 gr. 10 „ 5 » 1 „ 2 „ 2 „ 0-2 „ o-i „ IOO „ (T) The preparation of Solution A presents no difficulty; Solution B should be made up as follows : To the sodium phosphate dissolved in 40 c.c. of Water are added first the 2 c.c. of hydrochloric acid, then the 2 c.c. of hydrous ferric chloride and then the 4 gr. of calcium chloride dissolved in 40 c.c. of water, taking care to shake the mixture which I call Phospho-ferro-calcic solution. The addition of this last solution to the maceration throws down a slight brownish flocculent precipitate, formed for the most part of ferric oxide, which should be carefully separated from the liquid used for cultivations. CULTIVATION OF DIATOMS. 47 These solutions are kept separately; for use add 40 drops of A and 20 drops of B to a litre of ordinary water, in which has been previously placed 5 centigrs. of bran, 1 decigram of straw and a little quantity of ground moss previously washed in boiling water. When made in small quantities the cultivations are prepared in wide-necked flasks, stoppered with a plug of loose cotton wool. Large cultivations are made in crystallizing pans, &x. We have successfully employed square vessels which had been previously used as electric accumulators. It is well to take the precaution of sterilising all liquids by heating them in a water bath for a quarter of an hour, at a temperature of about 700 (a), so as to destroy any spores or fragments of Algae or even foreign diatoms, which those liquids may happen to contain. The cultivating liquid being ready it is fertilised by introducing into it a few healthy frustules. The cultivations should be kept screened from the direct rays of the sun. The best results are obtained by exposing the flasks to a northern illumination, and keeping them at a temperature of io° to 300 (c). When green Algas are produced their growth can be stayed by diminishing the light. Diatoms will also flourish in artificial light, such as gaslight, &c. Every 10 or 15 days fresh sterilised water, such as has been previously mentioned, should be supplied in the place of any water which has evaporated. If the cultivations "drag" (i.e.) develop slowly, this can often be remedied by adding a few drops of solutions A and B in the before- mentioned proportions. B. — Artificial Cultivation of Marine Diatoms. The Cultivation of Marine diatoms may be favourably effected in natural sea water. If this cannot be conveniently obtained, artificial water should be used and this can be made by dissolving : — Sea salt ... ... ... 250 grammes. Magnesium Sulphate ... 20 „ ,, Chloride ... 40 „ which should be dissolved in a sufficient quantity of water to make up one litre of solution. The liquid thus obtained is subsequently mixed with 9 litres of water immediately before using. The sea water is added to solutions A and B just as in the case of the fresh water, and similarly sterilised at a temperature of 7o°c. 48 CULTIVATION OF DIATOMS. A short filament of Zostera is added to it for organic nutriment. The water which has evaporated should of course be made up by adding sterilised distilled or rain water. Many diatoms, both marine and fresh water, require a special cultiva- tion. It is evident that in this summary we are unable to enter into these details and we therefore refer the reader to the original papers by Dr. Miquel, published both in Le Diatomiste and in the Annalcs de Micrographie. C. — Pure Cultivation of Diatoms. These cultivations are much more difficult than the preceding. In the first place a thoroughly healthy and fresh diatom should be isolated, which may be effected either by isolating it in the medium in which it is found by various artifices (capillary tube, pipette, hog's bristle, &c), or by breaking up the said medium after the fashion of Bacteriologists. As a rule it is by this last method, which is unfortunately rather lengthy, that an ordinary gathering can be turned to the best account. It is well known that this breaking up (J) is effected by mixing for example one drop of diatomiferous liquid with iooc.c. of nutrient liquid and by again diluting i c.c. of the resulting liquid in 09 c.c. of fresh liquid. This last-mentioned liquid is then apportioned for example in 10 Frendenreich flasks and submitted to cultivation. If the last liquid thus obtained be still too rich (i.e., contains many kinds of diatoms) it should be diluted a third and, if necessary, a lourth time. In this way cultivations in which not more than a single form occurs and from which subsequent cultivations can be made will eventually be obtained. These cultivations which we shall call Research Cuitira/ions, can be made in various ways. One of the most interesting is cell cultivation originated by Dr. Miquel, and described by him in " L'Annuaire de l'Observatoire de Montsouris," 1892-1893. The cells of Dr. Miquel are constructed as follows : — " A cell is cemented, without solution of continuity, to a glass slip, near the upper edge of which is bored an aperture about 2mm. in diameter, and over this cell is similarly cemented a thin circular cover- glass. In this way an entirely new kind of cell is produced, having ( r ) See Manuel d'analyse bact£riologique des eaux par le Dr. P. Miquel. Paris, Gauthier Villars, 1892. CULTIVATION OF DIATOMS. 49 an aperture near its margin ; it can be kept in a vertical position for the purposes of observation, and in a horizontal position during cultivation, f^~:,..,,:,.. ,'.;:;•;;•; ;:;,;:;;;l-: ■{■ :-f -■■■■■■* .i , ^--rn.r,,-, , , -^ m,, o £ gag 2 __ rrra n n Fig. 18.— The Miquel Cell. i. Tranverse section of the Miquel cell. LL. Glass slip. D. Aperture of 2 mm. cc. Cell. MM. Thin cover-glass. E. Liquid of cultivation. 2. I.ongtitudinal section. LL. Glass slip. O. Aperture. MM. Thin cover-glass. EE. Interior of cell. 3. Cell as seen on the stage of the Microscope. LL. Glass slip. EE. Cell. in which latter case it is then laid flat on the surface of the thin cover- glass. Thus the deposits, instead of being formed on the bottom of the ring, rest and become incrusted on the thin cover-glass; the diatoms, that are planted in these little cells, grow and multiply on the inner surface of the cover-glass, which enables their evolution to be followed for many months with the most powerful immersion objectives. I have some cultivations of this kind which are eight months old, and which still exhibit healthy and vigorous frustular species. " To replace the water which slowly evaporates through the apertures of the cells, the volume of liquid is made up to its original amount every eight days with a delicately-tapered pipette, filled with sterile distilled water. " By means of this apparatus various re-agents can also be made to act on the Algae by introducing them through the above-mentioned apertures without in any way deranging the position of the cultivation while under the microscope." I have myself experimented with these cell cultivations and can testify to the good results obtainable. I will only add, that if the results obtained by Dr. Miquel's arrangements are excellent, still better ones can be obtained by using Mr. Nachet's large inverted microscope, as I am doing at present. By employing this instrument the cell can be left in position during an entire observation without the diatoms being E 50 CULTIVATION OF DIATOMS. deranged, and they can be observed with any kind of objective, pro- vided that it has a correction sufficient for this length. As the instrument is admirably adapted for photography ('), photographs of high magnification can also be effected at any given moment. I have for several years used with this instrument a glass shade which covers up every optical part excepting the ocular ; the culture cells can then rest in position, and the instrument be always ready for examina- tion without any need of moving the shade. ZA— Mr, C. Haughton Gill's Cultivations. Dr. Miquel has found in Mr. C. Haughton Gill (whose other in- genious researches I shall describe hereafter) a worthy rival in producing his cultivations. In short, this skilful chemist, who died of heart disease while still at his work and at an age when he might fairly have looked forward to many more years of life, commenced his cultivations in 1891, but he had not at that time discovered the best way of proceeding ; moreover with the modesty which characterised the man, he attributed to Dr. Miquel all the success of his cultivations. "I have wasted," he wrote me, "half my time in preliminary researches and experiments, so that Dr. Miquel is in every way entitled to claim priority." I shall here summarily extract from his correspondence with me the information I possess concerning Mr. Gill's cultivations. I consider that I am only discharging a debt of honour by publishing this information, which my friend was prevented from giving to the world himself by his sudden death. The liquid which appeared to Mr. Gill to be the best for culti- vation was composed as follows : — A. Sodium chloride ... Sodium sulphate ... Potassium nitrate Acid Potassium phosphate Water B. Filtered spring water Solution A 10 parts by weight. 5 >» " 2-5 »> >> 2'5 5> >> 100 „ „ 100 parts by volume. °'5 » » To this solution he added a sufficient quantity of slaked lime to neutralise the acidity of the liquid and a small quantity of well-washed precipitated silica. Then subsequently he also added a small quantity of either a sterilised infusion of grass or " Diatom-soup," which he obtained by boiling a large quantity of fresh diatoms for a long time in water. ( ' ) See " The Microscope," by Dr. H. Van Heurck, English Edition, London, 1893, pp. 255, 256. CULTIVATION OF DIATOMS. 5 1 After filtration, this "soup" was preserved in sealed tubes. Later on again, he added to his solution some bone gratings, which he said dissolved rapidly in the liquid. At other times he added some well-washed grass roots. Although the Gill-solution contains considerably less ingredients than that of Dr. Miquel, and more especially as the salts of magnesium and iron are absent from it, Mr. Gill found that it was quite as favourable to the growth of diatoms as that of the learned French bacteriologist. Still later on however, Mr. Gill, who made his cultivations on a very large scale, modified his liquids and made them more like the Miquel-solution. The liquid which he employed during the last year of his life was made up of a mixture of four distinct solutions, as follows : — Solution i. — Crystallised Sodium phosphate (chemically pure) 2 Calcium chloride ( ,, ,, ) 4 Syrup of Iron chloride ( ,, „ ) 0-5 Strong solution of Hydro- chloric acid ( ,, ,, ) i"o Water ... ... ... ... ... ... 100 Solution 2. — Crystallised Magnesium sulphate (chemically pure) 4 „ Sodium sulphate ( ,, ,, ) 4 „ Potassium nitrate ( ,, ,, ) 4 Commercial salt (Sodium chloride) ... ... 8 Potassium bromide ... ... ... ... o-2 ,, iodide ... ... ... ... ... o-2 Water ... ... ... ... ... ... 100 Solution 3. — Crystallised Sodium carbonate (chemically pure) 4 Water ... ... ... ... ... ... 100 Solution 4. — Well-washed precipitated Calcium silicate ... 25 Water 75 Three cubic centimetres of these liquids are taken and a litre of drinking water or sea water (according to the circumstances of the case) is added to them ; the mixture is well shaken and is portioned out in conical flasks (Erlenmayer's vessels) of ico to 200 c.c, which are filled to a height of about three centimetres. The flasks, stoppered with cotton wool, are sterilised either in the oven or by making the liquid boil. The flasks should be allowed to rest for a week at least before planting them with diatoms. Solution No. 3 has a double action ; in the first place, it destroys the acidity of the liquid and then precipitates half of the calcium in the form of useful carbonate, for Mr. Gill considered that it was advisable that the diatoms should have at their disposal some solid matter on which they could live and subsist. 52 CULTIVATION OF DIATOMS. The purity of the products employed in the solution is, according to Mr. Gill, essential. If one wishes to succeed, too much care cannot be taken to ensure the absence of every trace of arsenic, mercury or silver. The presence of arsenic which is so often found in ferric chloride, in consequence of its being frequently manufactured with impure hydro- chloric acid, is one of the commonest causes of failure. As Dr. Miquel also points out, Mr. Gill discovered that the direct rays of sunlight are absolutely harmful to the greater part of the cultivation. He exposed his flasks to the direct sunlight on a board close to some glass windows which were situated N.N.W., at the same time inter- posing between the glass and the flasks a plate of pale green glass of the height of the flask and a wooden board slightly higher than the liquid. All the cultivations had been planted with one or more frustules, transferred with a capillary tube. "This," said he, "is the simplest and quickest method and also ensures absolute certainty that there is no other diatom in the final drop which is to be used for the purpose of planting the flask. The experiments of Mr. Gill were tried on a sufficiently large number of forms, among which we may mention PL Angulatum, Cymatopkura solea and Ellipiica, various Nitzschia, Cymbella and Navicula. All these forms were made the subject of numerous successive cultivations, and he had about ioo in his possession at the time of his decease. Some of these cultivations are unfortunately dead, perhaps from want of assimilable matter or for other unknown causes ; but a considerable number of them are still living. All of these, with voluminous notes by Mr. Gill, are in my possession. I hope to be able to follow these cultivations through a number of generations, and if the opportunity occur I intend to publish the results obtained from them. E. — Results of Experiments with Cultivations. Dr. Miquel has published in " Le Diatomiste " the technical methods of treating cultivations, and his experimental researches in the physiology, mor- phology, and the teratology of diatoms, which have resulted from the before- mentioned cultivations, have been published in the " Annales de Micrographie." We shall in a few words summarise the results obtained by the learned observer, but we refer the reader who desires a detailed account to the above-mentioned publication in which the experiments are fully and minutely described. i. Effect of Temperature. — A. Damp heat. — Diatoms flourish at a temperature between 150 and 300 C. CULTIVATION OF DIATOMS. 53 At 350 C. many species, especially the large forms, are considerably affected ; after having been subjected to this temperature for two hours, free diatoms no longer move, and in the greater part of them the endochrome can be seen contracted, and showing signs of a large number of air- globules. At the end of 15 days to 2 months most species, if planted in a new maceration, are restored to life. At 380 many species are absolutely destroyed. At 400 life becomes extinct in the greater part of the diatoms belonging to our temperate climate. After being submitted to this tempera- ture for two hours the protoplasm becomes perfectly glanular. At the end however of a few days Navicula, Mclosira, Fragilaria, as well as Surirella ovata, and Nitzschia thermalis are restored to life, while large Synedra, Nitzschia, &c, are absolutely destroyed. Between 400 and 45 ° all species are irrevocably destroyed. Observations show that, in proportion as the temperature increases, the endochrome contracts from the walls of the valves and throws off a number of oil globules ; if the temperature is further increased the protoplasm becomes green and then granular, and is detached from the wall of the valves, which is a sure sign of the death of the frustule. B. Cold. — When the diatoms are submitted to a temperature of o° C, to all appearances they scarcely appear to suffer at all, so long as the medium remains liquid, but should it happen to freeze the diatoms with very few exceptions succumb. 2. Effect of Dessication. — Experiments have shown that diatoms keep alive as long as they remain humid, but they die directly they are quite dessicated. 3. Effect of Light. — The rays which most favour the cultivation of fresh water diatoms are the yellow, blue, and green, arranged in order of merit. White rays are much less favourable. Semi-darkness is pre- ferable to a flood of light, though the latter favours the prolific growth of green algae. 4. Effect of Heat. — Cold considerably suspends or retards the progress of cultivations ; at a temperature between 50 and io° C. it takes from 10 to 12 days before the planted macerations show any well-pronounced traces of cultivation; between io° and 150 C. it only requires eight days, and between 150 and 20° C. merely four to five days. 5. Effect of Chemical Reagents. — Chemical reagents may be nutri- tive, indifferent, or toxic. By a toxic reagent Dr. Miquel means every chemical body which, when added to the maceration in a less proportion than one part to 1,000 parts by weight of the total quantity of cultivation 54 CULTIVATION OF DIATOMS liquid, suspends or checks the development of the diatoms. Chemical reagents have not the same toxic effect on all forms of diatoms. The following are the results which have been obtained by Dr. Miquel. Mercury chloride kills diatoms in doses between i in 30,000 and 1 in 40,000. Cupric sulphate acts like the former. Zinc sulphate in a dose of 1 in 40,000 considerably impedes the de- velopment of diatoms. Iron introduced in the form of ferric solutions is rapidly decomposed, and is thrown down as a fiocculent precipitate of yellow hydrated ferric oxide, the presence of which obstructs the development of diatoms if too much is added; in a very weak dose (see solution B.) it may assist the growth of diatoms. Arsenious acid acts very toxically on diatoms. It kills most of them even in so weak a dose as 1 in 30.000. The Mineral acids in doses strong enough to produce a sensible reaction produce a very harmful effect. Iodine produces the same toxic effect as zinc salts. Boric acid and Carbolic acid are not prejudicial if weaker than 1 in 10,000. Essential oils are opposed to the development of diatoms. 6. Effect of Anesthetics. — Chloroform has a powerful toxic effect on diatoms ; the vapours of Bromoform and Iodine also produce very harmful effects on them, but act more slowly. Lastly, the vapours of sulphuric ether and iodoform are less harmful, and carbolic acid has only a temporary effect. 7. Effect of Indifferent and Nutrient Substances.— Dr. Miquel has not yet published his experiments with these substances. 8. Forced Production of Auxospores in Cultivations. — Dr. Miquel, who has studied this phenomenon in connection with Melosira varians and Nitzschia palea has summarised his observations on this subject as follows : " 1st. — It is now unnecessary to rely on chance observations to observe the formation of auxospores in diatoms ; the experimentalist, by means of successive artificial cultivations of these algce in a pure condition, can most easily produce for himself millions of sporangial frustules of both filamentous and free diatoms. " 2ndly. — The size of diatoms is as a general rule established indepen- dently of the production of the spores or sporanges. The protoplasm of micro-frustules when near their size-limit increases in volume, escapes from TERATOLOGY OF DIATOMS. 55 the valves, and surrounded by a membrane which is primarily cellulose, passes out into the cultivations, usually assuming a very irregular form, but at the same time continuing to approach to that of normal mega- frustules. Many of these bodies, however, only complete their ultimate form when they begin to move. " 3rdly. — The primordial mega-frustules of bizarre and unsymmetrical shape acquire their elegant regularity by deduplication, a process to which they immediately submit. " 4thly. — Protoplasm which escapes from micro-frustules is not usually rendered effective in the glutinous or gelatinous substance, as recorded by various authors, and further, it is probable, as I have frequently observed, that the double auxospores placed side by side are due to the simultaneous germination of two micro-frustules on the point of dividing, the internal valves of which still adhere to another at certain points. "5thly. — It is still uncertain whether micro-frustules before their germina- tion are the subject of a special fecundation, the phenomena of conjugation therefore must be for the present withdrawn as the correct explanation of the cause of the re-establishment of form, in the case of the five or six species on which I have been able to make observations." § 6. Teratology of Diatoms. Dr. Miquel in his articles on cultivations published in " Le Diatomiste" expresses himself as follows : — "In addition to normal cultivations others can be produced, in which the predominence of certain physical and chemical elements can be in- tentionally exaggerated; then when the diatoms are able to grow in these media they acquire bizarre forms, which has induced me to call these cultivations Teratological. I have been able to follow these strange variations of form through three generations in certain Nitzschia and Cydotella. Nothing is more curious than observing these original diatoms getting embossed, asymmetrically attenuated and becoming absolutely un- recognizable ; in the case of Cydotella, which are ordinarily in the shape of a regular box, the valvular surfaces are seen to lose their circular form become oval, triangular, quadrate, or assume the appearance of unangular but very irregular closed curves ; at the same time the plane surfaces of the discs are warped and become undulated, the edges of the upper and lower surfaces of the cylinder begins, as it were, to form hills and valleys, while the markings of the Cydotella are nevertheless persistent and manifest themselves with these marvellous modifications superadded ; on the girdle face the alterations of shape which I record are very 56 TERATOLOGY OF DIATOMS. appreciable, and not unfrequently these box-shaped diatoms look some- what like flexible accordions which are in the act of being pressed in.- This bizarre morphology does not prevent these cell monstrosities from living and having a perfect endochrome. " The results obtained with teratological cultivations strike me as very remarkable. They explain, in the first place, how it comes about that diatoms of abnormal form are met with in nature ; it would seem that if only the growth of diatoms could be successfully arrested when they assumed the peculiar forms already indicated, not only could an infinite number of hybrid varieties cf the same species be created, but perhaps also the series of modifications could be followed, which slowly give rise to the transference from one species to another. So far I only feel con- fident on this one point, viz., that it is possible to produce very great deformities in the silicious carapaces of diatoms by means of cultivation." Every diatomist has occasionally come across deformed or modified valves and many of them have collected curious forms. The collection of Mr. E. Weissflog includes a large number of them. Amongst the most curious are the three figured below. •/ Fig. 19. — Deformed Diatoms. No. i represents a Navicula permagna, the half of the raphe of which is wanting, whilst in the same part of the valve the striae are radiant ; No. 2 is a figure of an abnormal Navicula maculata in which the raphe is present only for a short distance, while the striae become still more radiant and the valve assumes an almost oval outline. Lastly, in No. 3 the two raphes TERATOLOGY OF DIATOMS. 57 are placed nearly at right angles, and the puncta follow the same direction as the raphe. I have found other valves in the same collection, which are all quite as peculiar and show that neither striation nor outline are invariable. A few examples will bear out these remarks : — • Navicula lyra affords us a series of monstrosities : the margin is excised or the outline becomes sub-hexagonal ; the lyre is normal on one side of the raphe and infiexed towards the latter on the other side ; in another example it is undefined and indistinct ; on the two sides of the raphe the striae are duplicated close to the central nodule ; in another example there is a straight hyaline line, in addition to the lyre and between it and the margin ; lastly, in a further example, quite close to the central nodule there is a kind of round spurious nodule surrounded by a short radiant striation. Navicula Johnsoniana shows on the valve, spaces without striae and placed asymmetrically on the two sides of the raphe. In a Cocconeis scutellum the striation is regular on the lower portion of the valve, while it is undefined and takes all kinds of directions on the upper portion. In a Campylodiscus dypeus the valve is broadly excised on one side and the costae follow the outline of the excision. This does not always form a void space, the excision being filled up by a fine membrane showing an indefinite punctuation. In a Pyrgodiscus armalus all the large spines, with one exception, are wanting. A Mastogloia rhombica shows a sinuous raphe. In a Triceraiiuvi Favus one of the margins is strongly concave, and a hexagonal Triceratium dubium has its six sides very concave. In another Triceratium dubium there are only five angles, one of which is more acute than the others. An Auliscus punctatus has two false ocelli, while an Auliscus ccelatus has three equal and well-developed ocelli. A Biddulphia pukhella displays a cuneiform frustule. In conclusion, for space does not permit me to enumerate all the monstrosities in my possession, I will only mention further an Aulacodiscus Comberi having only three appendices, an oval Eupodiscus radialus, and an almost perfectly triangular Eupodiscus yonesianus. All these modifications of form, these monstrosities of excess and defect will exemplify what has been above described. The Honourable Jacob D. Cox, of Cincinnati, has made a special 58 TERATOLOGY OF DIATOMS. Deformed Diatoms. 700. This plate is traced from photographs and reduced one half, and the numbers of the figures correspond with the numbers of the paragraphs, all but No. 19 being in the first Class. TERATOLOGY OF DIATOMS. 59 study of deformed diatom valves, and has published an excellent pamphlet (') on this subject, a considerable portion of which I will proceed to give : — " I have," says the eminent American Diatomist, " provisionally arranged them in three classes : i. Those having indented or deformed outlines ; 2. Those having a double or multiple centre in the scheme of marking ;' 3. Those having the marking unsymmetrically varied. [Fig. 20.] I. — Indented or Deformed Outlines. 1. Navicula lyra E. — Santa Monica, Cal. ; fossil. One side boldly indented in a large, easy curve. 2. Triceratium favus, E. — Maranham Island, Pacific Ocean ; recent. One angle is wanting, two sides being joined by a curve, making one diameter, one-fourth less than the others. The process is present at the deformed angles, but is unsymmetrically placed. 3. Same species, from same gathering. A similar deformity carried further. The form almost semi-lunar, but the curve is not regular. The third process is wanting. 4. Triceratium robust um, Grev. = T. Sculpt um Shadbolt ? — Calvert Co., Maryland ; fossil. One of the angles is replaced by two smaller ones, giving an irregular trapezoidal form to the shell. 5. Triceratium jormosum, Brtghtwell, var pentagonalis, Grun. — Samoa Islands, Pacific Ocean ; recent. One of the indentations between the points of the star is nearly obliterated, and the two points connected by an irregular curve. 6. Same species and variety, from same gathering, similar deformity, but the line connecting two points of the star is more nearly straight, showing a tendency to revert to the triangular form of the type. 7. Same species and variety, from same gathering. The deformity here consists of a large umbonate protruberance in the centre of the shell, its surface covered by the irregular marking. 8. Same species, typical. — San Luis Obispo, Cal.; fossil. A typical triangular form, but with the central protruberance noted in No. 7. 9. Biddulphia rhombus, W. Sm. — Cuxhaven, North Sea ; recent. One side deformed by a large, irregular indentation. 10. Same species, same gathering. Similar deformity, but less pronounced. ( « ) Deformed Diatoms by Jacob D. Cox in Proceedings of the American Society of Microscopists for 1890. 60 TERATOLOGY OF DIATOMS. ii. Same species, triangular form — Triceratium striolatum, E. — A group of three specimens, of which two are the triangular forms, with regular and moderately convex sides ; the other specimen has one such side, but the other two curving into each other in a similar way to No. 2 above. The third process is wanting, but in its place are two spines, such as appear on the sides of the regular Biddulphia lorm. Variation in this species is so common that it would be easy to make a series of photographs showing the gradual passage of the Biddulphia into the triangular form. 12. Eunotia diadema, E. — Charleston, S.C. ; recent. The concave side irregularly curved, making the width of the shell much less in one place than elsewhere. The convex side is regularly eight-toothed. 13. Eimolia monodon, E. — Eoka Deposit, Sweden; fossil. A deep irregular indentation on concave side near one end, making the shell roughly comma-shaped. 14. Eunotia arcus, E. — Dolgelly Earth, Ireland (') ; fossil. A similar (but less marked) irregularity. In a recent gathering at Cincinnati, Ohio, these Eutwtias are found with so irregular reversed curves as to resemble wriggling earth-worms in outline. A specific distinction has been improperly based on this peculiarity. 15. Licmophora ovata, E. — Santa Monica, Cal. ; fossil. A large, shallow indentation on one side, giving a gracefully varied outline. 16. Rhaphoneis amphiccros, .Zs.-— Savannah, Ga. ; recent. One side of the shell a regular curve, the others very irregular. 17. Cymaiopleura clhpiica, Bred. — France; recent. The outline of the shell on one side irregularly wavy. 18. Grannnalophora marina, Kg. — Algoa Bay, Africa ; recent. One side wavy, unsymmetrical. II. — Double or multiple centre in the scheme of marking. 19. Mastogonia actinoptychus, Ehr.- — Richmond, Va. ; fossil. Elliptical form, with two distinct central spaces from which the costae radiate. 20. Stictodiscus Cahfornicus, Grev. — San Luis, Obispo, Cal. ; fossil. A fine circular specimen with two centres, the radiating costse approxi- mately regular on the outer limbs, but anastomosing in the space between the two centres. 21. Navicula Samoensis, Grun. ( = Nav. palpebralis, Gteg.l). — Samoa Islands, Pacific Ocean ; recent. In one half the shell, longitudinally, (') Wales.— W.E.B. TERATOLOGY OF DIATOMS. 6l a second medium nodule appears, with stria; radiating from it in all directions. 22. Biddulphia balcena, Ehr. = Triceratium formosum, BrighlweV. — Spitzbergen, Arctic Sea ; recent. A large Biddulphia form, in which the delicate marking radiates from four or more distinct points as centres. Ill Marking unsymmetrically varied. 23. Coscinodiscus robustus, Gnv. — Pabellon de Pica, S.A. ; guano. The areolation is so irregular as to have lost all hexagonal form. Its strong margin, robust habit, and its occurrence among typical specimens of similar size, etc., fix the specific relation. A similar example in same species was found in the Santa Monica deposit. 24. Arachnoidiscus Ehrenbergii, Bailey. — Santa Monica, Cal. ; fossil. The radiating costae, irregularly wavy, and anastomosing near the centre, where they also become fainter and hardly traceable. 25. Adinoptychus Heliopelta, Grun. — Nottingham, Maryland ; fossil. A specimen with five elevated rays. These are plainly distinguished at the central zone, but the undulations flatten out soon, and the outer part of the shell is quite flat and evenly areolated. The rim, with its irregularly scattered spines, is typical. 26. Triceratium affine, Grun. — Samoa Islands, Pacific Ocean ; recent. The areolation is so irregular as to lose entirely its hexagonal character ; this is the case all over the shell. Its size and outline, and its occurrence among numerous typical specimens show its relations. A second example has been noted on another slide from same locality. 27. Amphitetras antediluviana , Ehr. — Kiel, Baltic Sea ; recent. The central part of the shell is irregularly areolate, with a tendency to two centres. The typical forms, common in same gathering, have the central areolation evenly concentric. 28. Naviada elliptica, Kg. — Crane Pond, Mass ; recent.' The striation is irregularly wavy, especially at the ends. 29. E/if hernia turgida, Kg. — Berlin, Germany ; fossil. The costs? and areolation are so irregular as to destroy all pattern in one-half the shell and nearly so in the other. 30. Nitzschia scalaris Ehr. — Sodertelge, Sweden ; recent. In one part of the shell the keel is distorted, and instead of it appear two nodules on the face of the shell with irregularly radiating striae. " Whenever I speak of striation I mean to be understood that it is resolvable into dots, similar in character to those of the typical forms of same species, 62 TERATOLOGY OF DIATOMS. " In the examples which I have placed in Class II. and III. above, we see the distortion occurring by the miscarriage or interruption of the vital force which tends to produce the symmetrical sculpture of the shell of the diatom. In Class I. the cause of the irregularity would seem to be external and mechanical. It results, apparently, from the conditions of growth within a strong silicious box. When fission occurs the envelope of the new cells is at first flexible, and is often found very slightly silicified, but it acquires rigidity as the deposition of the silex goes on (') " Under these conditions, if we suppose that the diatom is better supplied with nutriment than common, and its circumstances are such as to make more vigorous growth, the valves of the new cell may tend to grow larger than the parent in all directions, and being con- fined by the strongly silicified coat of the mother cell, its own more flexible wall may fold upon itself and make a wavy irregularity of outline, such as is shown in some of the examples above noted. " The example of irregular wavy outline suggest also the conclusion that if, in the circumstances last supposed, the diatom were one whose shell presented alternate strong and weak points in its circumference, the indentations resulting would also be regular, and we should have a crenulate form of a shell normally smooth in outline. My own obser- vations have led me to think it probable that crenulated forms are thus originated. Once produced, further fissiparous division would tend to perpetuate the peculiarity, since the growing force in the new cells would force the flexible walls outward to fill the matrix. " It would not be till the process of conjugation is reached that the resumption of the normal type could reasonably be expected ; conse- quently it would be permature to conclude that the crenulation is a specific distinction, or even the mark of a lasting variety, until it is proven that after conjugation the new series of diatoms retains that form. " Considerations of this sort may assist us in reducing the enormous catalogue of species in the Diatomacece, a consummation devoutly to be wished." But not only may the valve undergo modifications and alterations, but the living frustule is liable to be attacked by certain diseases, which are only at present known to us by the alterations that can be observed in the endochrome, and it may moreover be attacked by parasites both externally and internally. (J) See Study of Isthmia nervosa by the Author, in Am. Journal of Microscopy, Vol. III., p. 97 (1878). TERATOLOGY OF DIATOMS. *3 It thus happens that on certain diatoms very singular filamentous parasites are occasionally found, which are thought to be algae. The Nitzschia especially are frequently attacked in this way, and in the Atlas to my Synopsis (pi. 7, fig. 22) will be found a representation of a Nitzschia a?ignstata infested in this way. Recently Mr. Grenfell (') has noticed various disciform diatoms having radiant filamentous appendices, which are very long, excessively thin, and fairly numerous. Every specimen of his gathering was in this condition (fig. 21). I have also personally established the existence of similar radiant appendices on the Coscinodiscus excentricus from a gathering made at Sheerness-on-Sea. Fig. 2i. — Diatoms with filamentous appendices. The important question in all these cases is whether the appendices are true parasites or whether they are actually produced by the frustule ; it is to be hoped that this problem will be solved by sub- sequent research. It is advisable in every case to draw attention to these appendices, as they are only to be seen with difficulty, and can only be seen to advantage when the living frustules are placed upon a slide and there allowed to dry of their own accord, the drop of liquid not being covered over with a cover-glass. It would be well to try the effect of analine stains on gatherings in a living state to see whether these productions are not more frequent than is at present believed. (') On the occurrence of pseudopodia in the Diatomaceous genera Melosira and Cyclotella, by J. G. Grenfell, Q.J.M.S., 1891. 64 TERATOLOGY OF DIATOMS. But not only the exterior of the diatom frustule suffers from the attacks of parasites ; Dr. W. Zopf has described under the name of Ectrogdla Bacillariacearum, a fungus which lives in the interior of living diatoms and specially attacks Synedra and Pinnularia. Its presence is manifested in the first place by an alteration in the shape and position of the chromatophores. The latter recede from the walls, contract in the direction of their length, and conclude by being closely applied to the parasites. At the same time the nucleus is dissolved, and the protoplasm contracts. Later on, in consequence of the growth of the parasite, and of the pressure which it exercises on the valves, the latter open, and the parasite can emit its spores exteriorly. At a meeting in London of the Royal Microscopical Society on the 19th October, 1892, Mr. C. Haughton Gill exhibited frustules of Pleurosigma, Nitzschia, and Cymbella, infested with a fungus. Mr. Gill was good enough to forward me photographs of the parasite and of his preparations, showing the latter in various stages of growth. In the letter, which accom- panies the packet, our kind and learned correspondent expresses himself thus : — " The fungus, if not directly identical with, appears to bear a consider- able resemblance to Zopfs Edrogella bacillariacearum (Nov. act. der Kol. and Leop-Carol Deutschet Akad. xlvii. p. 145). In some respects it resembles even more closely the Olpidiopsis described by Cornu (Ann. des Sc. Nat. series 5, xv.) as infesting Saprolegnia;. The sporangia, which first make their appearance (in Pleurosigma attenuatum) at about the beginning of November, are at first of a plain sausage-shaped outline, and their contents are nearly homogeneous. As they arrive at maturity, granules appear in the interior, and shortly afterwards the thick wall of cellulose becomes tumid at one point, and a beak or tube of ejection is put forth — you will find more than one spore sac at this very stage (on the slide tinged with black) detached from the shell of the diatom. "After some time the beak or tube bursts at its extremity and the zoospores issue rapidly into the surrounding water. I have not yet traced the further history of these zoospores. "A very curious point, which greatly needs confirmation by other observers, is this — this parasite appears in Pleurosigma attenuatum in November, December, and January. I have been hitherto quite unable to find it either before or after those months in this particular diatom, and during those months I have found it in no other species, though Nitzschia, Cocconemct, Pinnularia, etc., were abundant and were kept observed under identical conditions (in the same dish of water). About March the Nitzschia and Bacillaria became infested, while the Pleurosigma remained healthy PREPARATION OF DIATOMS. 65 If these facts are not accidental, but are confirmed by repeated and independent observations, they will need a good deal of explanation. Fig. 22. — Parasite infesting PI. Anqulatum. We give here (fig. 22) a representation of the parasite infesting the Pkurosigma attenuation in three different phases of its evolution. This figure is copied from the photograph sent us by Air. Gill. § 7. Preparation of Diatoms. After a gathering of diatoms has been made, they must be separated from the mud which often accompanies them, then deprived of their endochrome, and subsequently prepared either in balsam or dry. To isolate diatoms from mud, the entire mass is placed in a plate, a quantity of water just sufficient to cover them is then poured on to it, and the whole is exposed to the light in a well-illumined spot. After an interval, sometimes of a few hours, at others of a day or two, the diatoms may be seen to have come out of the mud and to be coating the surface of the water. The water surrounding them is then carefully drawn off and the diatoms thus exposed can be removed by means of a camel's hair pencil if the stratum is thin, or by means of a scraper or blade if the bed is thick. Thus obtained, the diatoms (') are placed in small tubes which are filled up with alcohol, and they can then be either prepared at once by a process of calcination on a cover-glass, which we shall afterwards describe, or they may be previously treated with acid. Fresh water ( r ) It is assumed that fresh water diatoms are being dealt with. In the case of marine diatoms it would be necessary to wash them two or three times in distilled water, so as to rid them of every trace of sodium chloride. 66 PREPARATION OF DIATOMS. diatoms are generally very silicious and are uninjured by being treated with acid. This, however, is not the case with many marine diatoms, which are very frequently only feebly silicious, and can only be sub- mitted, therefore, to a moderate calcination at the utmost. In treating diatoms with acid a small quantity is placed in a test tube, and covered over with one or two drops of nitric acid and the whole boiled for a (ew seconds (or sometimes for one or two minutes) in the flame of a spirit lamp, taking care that the dangerous vapours emitted do not injure the lungs or any instruments of precision. This operation should therefore be carried out in the open air or in the fume chamber of a laboratory. When the tube has cooled, it is filled with distilled water and left to rest. Some time afterwards the diatoms will be found collected at the bottom of the tube, the supernatant liquid is then carefully decanted or drained off and replaced by a fresh quantity of distilled water, and so on until the water shows no trace of acid. Then the water is decanted for the last time and the diatoms are finally covered over with a small quantity of liquid ammonia, which, after the lapse of some hours is in its turn decanted, and any traces of it that may then remain are got rid of by successive washings with distilled water. After this last operation the diatoms are perfectly cleaned and they are then placed in alcohol as previously stated. The mud of marine estuaries may be treated in the same manner, but great care must be taken to use only distilled water for washing. It has, in fact, the property of holding the clay in suspension, which can then be easily removed by decanting. If calcareous or saline water be used for the washings, the mud is precipitated with the diatoms. However, it sometimes happens that the diatoms are mixed with so much organic matter (as is the case with guanos amongst others) that the treatment above-mentioned is not sufficient. In such a case the mass must be submitted to a more complicated treatment. This is carried out in the following manner : — The material is treated with nitric acid as above described, especially when, as frequently occurs, the presence of calcium carbonate is suspected. It is then carefully washed and dried. Witnout this preliminary opera- tion the final product will contain a large quantity of calcium sulphate crystals, which it would be almost impossible to get rid of. The material, having then been treated as above, is placed in a deep porcelain evaporating dish ; a small quantity of concentrated sulphuric acid is poured over it so as entirely to cover the diatoms, and the whole is boiled for two or three minutes, PREPARATION OF DIATOMS. 67 By this operation the mass greatly increases in volume and the organic matter becomes carbonized. The spirit lamp (or Bunsen burner), which is being used, is then withdrawn, and, while the mass is still near boiling point, a saturated solution of potassium chlorate is added drop by drop to the water. As each drop is added a brisk effervescence is produced and the liquid is stirred with a glass tube. When a certain number of drops of potassium chlorate solution has been added — the quantity of which should be about half the volume of the sulphuric acid used — the liquid becomes quite clear ; the diatoms are then washed as in the operation first described. It may sometimes happen that after this operation, the diatoms are still not quite clean ; in this case the whole operation will have to be repeated. It is evident that very fragile diatoms and those but slightly silicified could not stand so energetic a treatment ; it should therefore only be used when the cleaning can be done in no other way. It should be again remarked that the last operation should only be carried out in the open air or in a fume chamber on account ot the chlorinated vapours, which are very dangerous to breathe, and moreover because the solution of potassium chlorate can only be added drop by drop without running the risk of a dangerous explosion and the projec- tion of the matter out of the tube. The diatoms having been cleaned in this manner, it is then necessary to prepare them. Various methods may be followed, but that which gives the best results consists in burning the diatoms on a plate of mica or a cover-glass. I have adopted this method ever since I was first informed of it by the late Mr. De Brebisson, more than 25 years ago. This process, together with the preliminary and subsequent opera- tions, has been described at full length by my friend Professor H. L. Smith, the learned American, so well known by his many excellent works on diatoms. I quote the article which he published on this subject in "The Lens," the journal of the State Microscopical Society of Illinois. (') Preparation of Diatoms according to Prof. H. L. Smith. — -The follow- ing article, in the words of Prof. Smith, deals with the rapid method of preparing from crude material and with a mode of mounting invariably on the cover of the slide : — t; The gatherings should not be dried, but kept moist, in phials with a little creosote to prevent mould. I very much prefer to examine whole frustules, with both valves adherent, or if filamentous, still ( « ) The Lens (1873), ii., pp. 209-212. 68 PREPARATION OF DIATOMS. cohering. And I have many bottles of preparations for mounting, which are nearly as clean as though they had been treated with acids. And many of the most interesting preparations which I have were never boiled in acids. Of course, very much depends upon the skill and carefulness of the gatherer, and a little patience and judgment will enable any one to obtain the crude material tolerably pure. Only a few days ago I made a gathering of JVitzschia, in which I have the frustules almost as free from foreign matter as though they had passed through the most elaborate acid and chlorate of potassa treatment. " Supposing, then, that one has before him a phial which will hold a considerable quantity of water compared with the sediment in it, the latter composed more or less of diatoms. We proceed thus, and if it has stood for some days, perfectly undisturbed, so much the better. The bottle is twirled rapidly, and the lighter material rising up in the axis will soon diffuse itself throughout the water. " Allowing it to settle for two or three seconds, until to the eye the grosser portions have just been deposited, all that remains floating is now poured off into another phial, and it is from this stock that we are to separate the diatoms and sand from the clay and organic matter. The material poured into this second bottle is allowed to settle until the water simply appears milky or cloudy ; the time will vary according to the minuteness of the diatoms, and can only be judged of from experience, say one minute, when all that remains floating must be poured off, and thrown away, unless there are very minute forms which it may be desirable to separate. The phial is again to be filled with rain, or distilled, water, (hard or lime water should be strictly eschewed) and again shaken up. As soon as the heaviest deposit touches the bottom, the rest should be poured off into a third phial, leaving say about one-fourth the amount behind in the second phial. This third phial will now consist mainly of sand and diatoms, with lighter organic matter and pure clay; the last two can be removed by elutriation ; for this purpose, fill the phial No. 3 with water, and after well shaking allow it to settle two to five minutes, pour off and throw away the slightly milky water, and repeat the operation, allowing it to settle a somewhat longer time ; the operation may be repeated a third time, when particles, suspended after an interval of eight or ten minutes, may be poured off. Often, after the first settling of bottle No. 2, the diatoms will rise more pure in the mass by twirling the bottle than by shaking it up. "A little practice and care will enable anyone to separate certain diatoms according to size. I had a gathering of Plcurosigma Spencerii from Scioto PREPARATION OF DIATOMS. 69 River, O., sent to me, but although it had been chlorated, still, when a mounting was made, not more than one or two frustules would be in the field of view, the great mass being either smaller forms, or fine frag- ments of silex ; by careful watching and testing the time when the different sizes would remain suspended, I have made from this a pre- paration, which will show hundreds where before were scarcely any, and which would never be recognised as the same gathering. Supposing now a trial shows us the diatoms tolerably abundant, the trial being made by heating in the manner presently to be described ; the phial is filled with alcohol and water, half and half. Some samples of alcohol leave behind a scum after evaporation, especially noticeable after burning in the mode presently to be described, and water which will leave crystals, or any scum, must be avoided. The beauty of the preparation will largely depend upon being particular in this matter. " For mounting diatoms I invariably place a drop of the fluid con- taining them upon the cover, never on the slide. The alcohol and water will spread out on the slide, but will remain heaped up on the round cover, like a plane convex lens. I prepare a little stand, of quite fine wire (so as not to conduct off too much heat), bent at right angles and inserted into a base ; the free end is bent into a ring, and upon this ring is placed a square plate of very thin iron, (') (such as is used for the so-called "tin-types" in photography, with the Japan burned off), held in place by bending the corners of the square over the ring, loosely, to allow expansion, without bending when heated ; upon this plate the cleaned cover is placed, and then, by means of a pipette, a drop of the alcoholic liquid with the diatoms is placed upon it, and the spirit lamp applied below. The alcohol takes fire and is allowed to burn out ; the flame of the lamp is then placed beneath, and the rest gently boiled, the remaining alcohol escaping during this ebullition causes the diatoms, by this very act, to distribute themselves very evenly over the cover, and all matting is effectually prevented. It is better, after one perceives that this even distribution has taken place, not to push the heat so as to make large bubbles again, but to slowly evaporate until dry, after which the full power of the flame must be applied until the iron plate and the glass cover are red hot ; at first the mass of diatoms, etc., will become black, but as the organic contents and debris burn away there will finally remain only the silex nearly white. I invariably burn in this manner on the cover; even the specimens which have been prepared with acids, ( ' ) I prefer to use a small square piece of platinum foil, with the corners folded back, and held tightly with a pair of forceps.— H.V.H. 70 PREPARATION OF DIATOMS. for the diatoms thus treated when mounted appear much sharper and cleaner. (') The amount of heat, if the diatoms are rigidly silicious, as most of them are, may be the full power of an ordinary alcohol flame continued for some time, but if they are imperfectly silicious, care must be exercised in the burning. " I invariably use old balsam for mounting, just as bought from the shops, especially if I wish to have a specimen which will bear immediate handling, or be ready to be sent off as soon as mounted. Allowing then the cover to cool, while the slide is being cleaned to receive it, I place a drop of the balsam, which must not be fluid, only viscous, on the middle of the slide, and now with this pick up the cover from the little stand where it has been heated. The diatoms will be so fastened by the heating, that but few will flow out from under the cover, if any, in the subsequent treatment. I now hold the slide over the flame of the lamp (which should be much smaller than when used for the burning) until not only all under the cover is a mass of small bubbles, but until very large bubbles, balsam steam, appear ; the flame is removed so soon as the bubbles are observed all running to one edge. I press down the cover at this place by a mounted pin, and start them in the opposite direction. This may seem unnecessary, but long experience shows that this is the better way to get rid of them ; during this the slide is held somewhat obliquely, the cover is kept from slipping by the pin, and if all the bubbles do not disappear, then, with a very small flame, heat is applied just beneath the obstinate ones, the slide being held slanting, and that part upwards where the bubbles are nearest the edge of the cover. The description is longer than the actual process, and the slide, when cool, is ready for immediate use. Perhaps I am wedded to old ways, but after trial of fluid balsams, without heat, I have always come back to the old way ; still, for selected diatoms, some of these preparations of balsam are good. If the diatoms are to be mounted dry, always the best way, if lor real study, I make a ring of the zinc white in balsam (2) (sold by the opticians) and which in a moment or two is sufficiently hard to receive the cover, and (') I entirely agree with Professor Smith in his opinion. — H.V.H. ( - ) This cement is made as follows : — Some white of zinc boiled in oil is taken and all the oil removed from it by means of repeated washings in benzine. The white paste is slowly dried on a filter paper and then added to a thick solution of Dammar balsam dissolved in benzine. Generally speaking diatoms should be mounted dry as rarely as possible, for it is usually impossible to keep dry preparations without deterioration. They all ultimately become invaded by a mould arising from the varnish. There is, I believe, but one varnish which is suitable for mounting diatoms dry, and which will usually prevent the formation of this mould ; viz., a thick alcoholic solution of gum-lac. — H.V.H. PREPARATION OF DIATOMS. 7 I never runs in ; after standing an hour or two I give a finishing ring of same, or the usual black varnish on the outside. I think anyone who will adopt the mode of mounting on the cover, and subsequent heating, as above described, whatever may be the rest of the pro- cedure, will never consent to give up this part, since it effects so even a distribution and such destruction of residual organic matter, and gives such increased brilliancy to the preparations ; sometimes, if the acid has not been thoroughly washed out of acid-treated speci- mens, snappy explosions will occur when the alcoholic mixture is heated ; of course, the remedy is to pour off, and replace with pure water and alcohol." Mr. Fred Kittoris method. — -The learned English diatomist, Mr. Fredk. Kitton, has been good enough to send me a manuscript note of the method which he adopts in preparing diatoms. The reader will find in it much important information. " When cleaning diatoms," says Mr. Kitton, " I prefer to add at the end of the operation some small crystals of potassium chlorate, which I find easier to use than the aqueous solution of that salt, for if you add the latter rather too abruptly it produces such a brisk effervescence that the contents of the tube are liable to be projected. When the mass has been bleached and all acid got rid of by washings with pure water, I drain off the latter and pour 30 to 40 drops of concentrated liquid ammonia into the test tube which I stopper with a cork. The tubes which I use are 15 centimeters long and two centimeters in diameter. I leave the ammonia to react from half-an- hour to six hours. I then add 15 grammes of distilled water, and I give the tube a good shaking. When the diatoms have fallen to the bottom of the tube I draw off the supernatant water, which is often very thick, I add a fresh quantity of water and give it another shaking. I proceed in this way until every trace of ammonia has disappeared. Guanos, marine soundings, and certain fossil deposits require a different treatment. " When every trace of acid has disappeared, I boil the gathering for three or four minutes in about 30 grammes of water, to which I add a piece of soap the size of a pea. When the diatoms have fallen to the bottom of the flask I remove the soapy water and boil the gathering in pure water. If these methods have been thoroughly carried out the residue will only consist of sand and diatoms. Should the gathering contain any large or heavy forms which I wish to secure for selection I allow the liquid to rest for 20 or 30 seconds, to allow them to 72 PREPARATION OF DIATOMS. fall to the bottom ; then I decant the liquid which will contain fine sand and small diatoms. To separate the sand from the latter I have successfully pursued the following method : — " I take two glass slips A and B. On A I place a drop of distilled water and on B a small quantity of the liquid to be treated. I give B a slight rotatory movement, keeping it in a horizontal position, which accumulates the sand in the centre of the liquid, and I then incline the slip towards one of its corners ; the diatoms are drained off and fall into the drop of distilled water on slip A. This water is then spread on cover-glasses. By this method some gatherings which seem to be quite worthless furnish very good preparations, although it is often necessary to add several drops of B to the slip A. I recom- mended this method of working to one of my friends who complained of the trouble which a gathering of the mud from a rice plantation was causing him. In thanking me shortly afterwards he expressed his astonishment at the number of different forms he had obtained from this gathering, which at first appeared to be valueless. "The preparation of deposits of marine origin is generally very diffi- cult in consequence of the diatoms being apparently united together by a silicious cement which it is very difficult to get rid of without destroying the diatoms. I succeeded completely however by proceeding as follows : — -A small portion of the material to be treated having been placed in a test tube I add some nitric acid, I boil it and wash to get rid of all lime. I then treat it with sulphuric acid and decolourise the mass which has generally turned brown under the action of the potassium chlorate. After a careful washing, the mass is boiled again for a minute in a small quantity of water, to which a little sodium carbonate has been added. After a subsequent washing the mass is returned to the test tube and shaken until it disintegrates. If this result is not obtained it should be boiled again in a solution of caustic potass, and just as it falls to pieces it should be poured into water to which some hydrochloric acid has previously been added. " When a gathering of living diatoms has to be dealt with, and especially forms which develop in chains, a portion of the gathering is treated with acid which is added to the other portion which has not been used. In this way preparations are obtained in which the two faces of the frustule and its mode of development can be studied at the same time. " I have often tried to use the method recommended by Professor H. L. Smith, but I have never been so successful as when I have PREPARATION OF DIATOMS. 73 previously got rid of all alcohol by washings. I prefer to allow the diatom iferous liquid to dry slowly without burning which has always lurnished me with preparations containing some diatoms united in groups and in bands. " Nor have I been more successful when I have put the balsam immediately on the diatoms, more particularly when I have been pre- paring large and convex forms such as the Coscinodiscus or Aulacodiscus ; the balsam does not penetrate into the interior. In these cases I previously put a drop of oil of turpentine on the diatoms and when this has thoroughly penetrated the valves I add the balsam and let the whole rest in order that the balsam may slowly take the place of the oil, which is volatile. " I have found this necessary sometimes even when using styrax, although this is more fluid than Canada Balsam. " Mounting diatoms dry is the easiest process of all, but to prevent as far as possible the diatoms spoiling, which often happens after a short interval, in the first place ihe diatoms must be perfectly washed in distilled water, then the black varnish used for making the cell should not contain any oily matter, as is often the case, and this varnish should be thoroughly dry before applying the cover-glass, which is made to adhere by heating the glass-slip. The black varnish may be advantageously replaced by hard Canada Balsam dissolved in benzine (I)." Mr. / Kinker1 s Method. — My friend, Mr. J. Kinker, is the skilful and learned diatomist, of Amsterdam, who has produced many very remarkable type-slides made after Moller's method. He has shown me in his own laboratory the method which he employs for cleaning diatoms, and we can testify to the advantage of his mode of operation from personal experience. He begins by getting rid of the sand by successive washings, and of the lime by treating for a day in hydrochloric acid. Then he washes thoroughly and boils the deposit for fifteen minutes in sulphuric acid, to which has been added a few drops of nitric acid, the fifteen minutes being reckoned from the moment Mr. Kinker lights the gas. The boiling is effected in a small glass flask or retort, fitted with a glass stopper, terminating in a long curved tube, which is plunged into an alkaline solution to absorb the acid vapours. The flask is placed in a sand bath. 1 ) See our previous footnote on gum-lac varnish, p. 70. — H. V.H. 74 PREPARATION OF DIATOMS. The liquid having cooled, the diatoms are washed and then boiled in a solution of sodium carbonate of a strength depending upon the circumstances of the case. This operation, which is carried out in a porcelain dish, is carried on for ten minutes. After again cooling, the liquid is decanted and water, containing a certain quantity of nitric or hydrochloric acid, is added. After again decanting and washing, the deposit is poured into a long narrow flask, so as to fill only a third of it and the whole is thoroughly shaken for one or two minutes. The shaking separates the material ; water is then added, after which it is allowed to rest for a tew minutes. The clear portion is then decanted by means of a pipette and the deposit is again shaken and the subsequent operations repeated, and so on as long as they continue to give a good result, i.e., enable fresh diatoms to be separated. The mass which is ultimately obtained from these successive operations is separated by decantation, if necessary, from any sand which may have been left behind, and placed in a large flat-bottomed measure glass which is filled up to the top and decanted into a measure No. 2 at the end of a minute, this is again decanted into a measure No. 3 at the end of three minutes, then again after five and ten minutes. The operation is performed six times in succession, and timed by a watch, then the diatoms will be sufficiently well separated according to their size. The diatoms are then placed in a small test tube, and as much water as possible is drained off, which should be replaced by pure alcohol. This alcohol is then drained off again and twice replaced by isobutylic alcohol. The diatoms, intended to be used for type-slides, are preserved permanently in this isobutylic alcohol. When preparations are made the diatomiferous liquid is placed, by means of a pipette, upon cover-glasses, which may then be used either for immediate mounting or for the purpose of selection. The isobutylic alcohol cannot be mixed with water ; it has the advan- tage of drying very slowly — taking at least several hours — and of avoiding the accumulation of the diatoms during evaporation : the valves remain absolutely in the same position in which they are placed at the moment when the drop falls, but they do not stick to the cover-glass as is the case with ordinary alcohol. Professor Brntis method of preparation. — Professor Brun, the enthusiastic diatomist of Geneva, described in 1887 a method of preparing diatoms, which, according to experiments I have made, gives excellent results. He has thus described his operations : — " A large number of recent microscopical writers," says Mr. Brun " have devoted their attention to pelagic gatherings, to those from lacustrine PREPARATION OF DIATOMS. 75 and marine muds and to fossil deposits. In such are found Polycystins, Radiolaria, Globigerina, Foraminifera, Sponges, Diatoms, and many other infinitely small and very varied organisms. In the marine muds of soundings only dead and mummified species are found. It is only at the surface of seas and lakes that living examples exist, where both air and light are abundant, and if in the deep muds a few specimens are occasionally met with in good condition, it is only due to the fact that they have dropped from the surface and that they have but lately ceased to live. "A naturalist often experiences great difficulty in separating these organisms from the pulverulent or crystalline mass {silicious, argillaceous or calcareous), of which the greater portion of soundings consist. These substances, often mixed for centuries with organic detritus form usually a pasty or plastic mass, which may sometimes be even like tar, and is very troublesome and difficult to separate. A large quantity of volcanic ashes may also be frequently found mixed up with them. Sometimes the sounding only consists of mineral material without any trace of organisms. " In order to study organisms having silicious shells, e.g., Polycystins, some Radiolaria, and especially Diatoms, it is indispensable to entirely destroy this bulky organic matter. In guanos excrementary detritus are abundant. They resist to an extraordinary degree the process of putrefaction and even dissolvents, hydrochloric and nitric acid and chlorine. All these organic detritus are equally incapable of being levigated by reason of their varying specific gravity, and more particularly because mineral particles so persistently adhere to them. "The following process effects the complete destruction of all this organic matter, and as it does not give off any acid vapours it has the advantage of not necessitating the use of a special laboratory or a strong up draft current during cleaning. It also gives results superior to any treatment with potassium chlorate or permanganate, or with nitric acid, the chemicals usually employed, since all these give off acid and corrosive vapours. "The desiccated mass (which may be pulverulent or compact) is treated in a phial with diluted hydrochloric acid to remove the calcareous matter. The phial should be sufficiently large to hold all the viscous scum which the calcareous matter produces when it is thus intimately mixed up with organic matter in a state of decomposition. When these salts have been completely dissolved the liquid and the mud are placed on a filter paper, on which the insoluble deposit is washed, and then dried on the same filter paper. 76 PREPARATION OF DIATOMS. " This dry deposit is then put into a phial and twice its volume of concentrated sulphuric acid poured on it. This is allowed to act for several hours, during which it is frequently shaken. The mass will grow black. Guanos require from five to six times their volume of sulphuric acid. This acid is the only efficient solvent of excrementary debris, and even then most of it can be removed by decanting three-fourths of the sulphuric liquid after leaving it to rest for a sufficient time. On this thick gruel-like and blackened matter some coarsely-powdered potassium bichromate is then added. It should be added by small successive doses, giving it a good shake each time. The mass becomes heated and oxygen is often given off. It should be stopped as soon as its colour has changed from black to red, or when crystals of chromic acid have been formed. In this treatment the organic matter is carbonized by the sulphuric acid, and the nascent chromic acid effects its combustion. The preliminary washing with hydrochloric acid is made so as to avoid the formation of lime sulphate. " To the above liquid is added water little by little. The mass again becomes heated. An abundant supply of water is then added. The colour of the resulting deposit is now comparatively white. It is then carefully washed by decanting. The last decantings are made with dis- tilled water. It is then ready for use. For this purpose it is diluted with distilled water, and the mixture dropped on to large cover-glasses, on which it is dried. From these cover-glasses the selection of species is made." Preparations with Styrax and Liquidambar. — Towards the middle of the year 1883 I disclosed a new method of preparation, which I had myself practised for some considerable time. I have given up Canada Balsam and I use Styrax instead, which, while being easier to manage, has a considerably greater index of refraction and shows the details of diatoms much more clearly. Since I introduced this medium to the public I have had the satisfaction of seeing it adopted by the most competent diatomists. I will therefore shortly explain the method of preparing and using Styrax. Styrax is a natural balsam which exudes from the Styrax Orientalis Miller, a native of Asia Minor. It must be bought in the raw state as sold commercially, when it appears in the form of a soft, greyish mass. A thin layer of it should be spread on a plate and exposed to the air and light until it becomes sufficiently hard and has lost all the water which it contained. This is then dissolved in a mixture of equal parts of alcohol and PREPARATION OF DIATOMS. 77 benzine (not to be confused with petroleum benzine) or, if preferred, in a mixture of sulphuric ether and absolute alcohol, and filtered through a filter paper. The following is the way in which I use the solution thus obtained, whilst I also give a description of the mode in which I have made my preparations for the last ten years or more — -the mode indeed in which all my type collections of the Synopsis were prepared : — I begin by placing the cover-glasses on a large plate of glass, or on a thick piece of cardboard, and on each of the former, by means of a pipette, I put a large drop of distilled water, on which I carefully let fall a small quantity of diatomiferous liquid. (') The diatoms disperse in the drop of distilled water, which is consequently slightly agitated. The cover -glasses are then covered over with a bell glass and left to evaporate of their own accord. When this is completed the cover-glasses are taken one by one and heated to red heat on a plate of platinum and put back on the large plate of glass where, after having received a drop of very fluid solution of styrax, they are again left under the glass bell to evaporate. In a few moments the layer turns white, but this phenomenon need not cause anxiety (it does not occur with the solution in chloroform), and at the end of 24 hours the benzine is completely evaporated. The cover-glass is then turned over and placed on a glass slip and heated gently, preferably with a Marie bath (hot water bath). Having got rid of the air bubbles, if there be any, by means of a clip, it only remains to remove any superfluous styrax from it, when cold. Liquidambar is preferable to Styrax. This balsam, which is obtained from the Liquidambar S'yraciflua is not met with commercially in Europe, but it can now be purchased from Messrs. Paul Rousseau & Co., 1 7, Rue Soufflot, Paris, purified and hardened according to our method, or in solution (when it is made up either with chloroform or benzine, and is preferable for mounting diatoms). Liquidambar is more easily managed than Styrax and has a little higher index of refraction. Preparations in very refractive liquids. — Various substances possessing a high index of refraction have been proposed for preparing diatoms in, e.g., Monobromide of Naphthalin, Sulphur and Phosphorus dissolved in carbon bisulphide, &c. All these substances are very troublesome to use, and the last two do not keep. They can therefore only be employed tempor- arily and in those cases in which very indistinct details have to be studied. (T) I preserve my diatoms in alcohol, which I decant before using, and substitute distilled water. 78 PREPARATION OF DIATOMS. However, Prof. H. L. Smith has invented a medium which possesses an exceedingly high index of refraction, viz. : 2-25 to 2-4. We have given a detailed description of the way in which this medium is pre- pared in the last English Edition of our Treatise on the Microscope, and we refer to this work for the details on this subject ('). Systematic preparations of Type Slides and selected d'atoms. — Every microscopist is aquainted with the admirable type slides which were first introduced by Mr. J. D. Moller of Wedel, in 1867. I have a most vivid recollection of the appearance of the first slides (many of which are in my possession) and the seniation which they produced in the microscopical world. Mr. Moller employs a specially constructed microscope to make his type slides, and he adopts his own particular methods, which he has hitherto disclosed to but three or four persons, of whom I am fortunately one. I have now known it for a long time but am under an obligation not to reveal anything in connection with the subject. Other professional preparers and enthusiastic amateurs have applied themselves in the same direction, and if their results are not as per- fect as Mr. Moller's — a fact which anyone who has been initiated into his secret must recognise — they at least approach very closely to per- fection ; the type slides of Thum of Leipzig for example are deserving of all praise. Type slides proper have not hitherto, so far as we know, been made other than by Moller and two enthusiastic and skilful amateurs, Mr. J. Kinker, of Amsterdam, and Mr. E. Weissflog, of Dresden, both of whom use Moller's process, and have produced genuine works of arts. Mr. E. Weissflog, especially, has made himself quite master of the art, and has produced most important type slides, as for instance that of Santa Monica, which contains about 600 forms. Such work requires long and difficult application. In connection with type slides we must not omit to mention the prepara- tion of selected diatoms, i.e., preparations containing one or more isolated diatoms. These preparations are very valuable, and every diatomist ought to know how to make them. The methods moreover are very simple, and have been fully described by Mr. H. Peragallo, the eminent French diatomist, in his work on " Les Diatom'ees de la Bate de Villefranche" (2) and I shall now quote all the passages in which our learned correspondent describes them : — " I ( « ) The Microscope, London, 1893, p. 305. (2) Paris, Librairie BaillieYe, 1888, ^0oos -*• P- 394- Dillwyn (L. W.). — Britijh Confervas. London, 4to, 1809. [See hereon Mr. F. Kitton's Notes on the genera and species, J.Q.M.C. (1S83), i., ser. 2, p. 166; Journ. Microg., Paris (1SS3), viii.; also Grossbrittanniens Conferven Nach. Dillwyn, fiir deutsche Botaniker bearbeitet, by Dr. F. M. Weber. Gottingen, 1809]. BIBLIOGRAPHY. I I 5 Donkin (Arthur Scott). — On the marine Diatomaceae of North- umberland, with a description of iS new species. T.M.S. (1858), vi., pp. 12-34, 3 plates; Q.J. M.S. (1861), i., pp. 1-15. See also thereon Walker Arnott, Q.J.M.S. (1858), vi., pp. 164-5, and in reply Q.J. M.S. (1859), vii., pp. 5-9. The Natural History of British Diatomaceae, illustrated with plates by Tuffen West. Parts 1-3 (all published), 12 plates; 105 figures of Navicula ; 8vo. London, 1871-72. Review of the same in Q.J.M.S., Vol. XIV., p. 93. On a species of filamentous diatom new to Britain, Q.J.M.S. (1858), vi., pp. 11-12. On several new and rare species of fresh water Diatomaceae discovered in Northumberland, Q.J.M.S. (1869), ix., pp. 287-296, 1 pi. Notes on certain fresh water species of Diatomaceae. Q.J.M.S. (1869), ix., PP- 397-400. Drummotid (James L.). — On a fossil infusoria found in the County Down, Ireland. London Mag. Nat. Hist. (1839), hi., n.s , pp. 353-359. Ehrenberg (C. G.). — Mikrogeologie, pi. 28, writing chalk, Gravesend. PL 15, Mourne Mountains. Leipzig, 1854. Fossile Infusorien aus England. Ueber Lager fossiler Infusorien in Ireland., Berl., Bericht (1842), pp. 335-339 Firth (William A.) and Swanston (Wm.). — References to the diatomaceous deposits at Lough Mourne and in the Mourne mountains. Proc. Belfast Nat. Field Ci. (1888), hi., ser. 2, pp. 62-64 (with list of species by Mr. Lawrence Hardman). Gregory (W., M.D.). — Notice of a diatomaceous earth found in the Isle of Mull. T.M.S. (1853), i., pp. 92-99. Additional observations on the Diatomaceous Deposit of Mull. Q.J.M.S., (1854), ii., pp. 24-28. Notice of the new forms and varieties of known forms occurring in the diatomaceous earth of Mull, with remarks on the classification of the Diatomaceae. Q.J.M.S. (1854), ii., pp. 90-100, pi. IV.; Edin. Royal Soc. Proc. (1857), hi., pp. 176-177, 204-207. On a remarkable group of diatomaceous forms, with remarks on shape or outline on a specific character in the Diatomaceae. T.M.S. (1854), hi., pp. 10-15, PL II . On a post tertiary lacustrine sand, containing Diatomaceous exuviae from Glenshira, near Inverary (1855), hi., pp. 30-43, pi. IV. On some new species of British fresh water diatomaceae, with remarks on the value of certain specific characters. Edin. Bot. Soc. Proc. (1855), pp. 38-41. [l6 BIBLIOGRAPHY. On the presence of Diatomaceae Phytolitharia and sponge spicules in soils which support vegetation. Rdin. Bot. Soc. Proc. (1855), pp. 69-72. Report on the Diatomaceae collected during a botanical excursion to Falkland and the Lomond Hills. Edin. Bot. Soc. Proc. (1855), P- 74- On the post tertiary Diatomaceous Sand of Glenshira, pt. II., con- taining an account of a number of additional undescribed species, illustrated by numerous figures drawn from nature. T.M.S. (1856), iv., n.s., pp. 35-48 pi. V.; (1857), v., pp. 67-88, pi. 1; Edin. Roy. Soc. Proc. (1857), hi., pp. 358-366- Notice of some new species of British fresh water diatomaceae. Q.J. M.S. (1856), iv., pp. 1-14, pi. 1 ; Edin. Roy. Soc. Proc. (1857), hi., pp. 306-308. On new forms of marine Diatomaceae found in the Firth of Clyde and in Loch Fyne, illustrated by numerous figures drawn by R. K. Greville. Ed. Roy. Soc. Trans. (1857), xxi., part IV., 6 plates, 4to. Edinburgh, 1857 ; extract therefrom, QJ.M.S. (1859), vii., pp. 60-64; Edin. Bot. Soc. Proc. (1858), v., pp. 144-146. On new forms of Diatomaceae from the Firth of Clyde. British Ass. Report (1S56), pt. 2, pp. 83-84. Greville (R. K.). — Scottish Cryptogamic Flora, 6 Vols., col. pi., 8vo. Edinburgh, 1823-1828. The English Flora of Sir J. E. Smith (Diatomaceae by Dr. Greville, Vol. V., part 1, pp. 401-415). London, 1833. Report on a collection of Diatomaceae made in the District of Braemar by Prof. Balfour and Mr. G Lawson. 1 plate. Edinb. Bot. Soc. Journ. (1855), pp. 7-9, A. and M.N.H. (1855), xv., Ser. 2., pp. 252-261. Descriptions of new species of British Diatomaceae chiefly observed by the late Prof. Gregory. Q.J. M.S. (1859), vii., pp. 79-86 Grove (Edmund). — List of Diatomaceae observed in a gathering from the River Lea. J.Q.M.C. (1894), v., ser. 2, p. 344 ; references thereto by G. C. Karop. J.Q.M.C. (1894), v., ser. 2, p. 366. Le Diatomiste (1894), ii., pp. 104, 132 ; La Nuovo Notarisia (1895), p. 54. Harkness (Robert). — Diatomaceae found in a sub-fossil state in Dumfriesshire. Edin. Bot. Soc. Proc. (1855), p. 54-58; Edin. New Phil. Journ. (1855), ii., pp. 54-56. Harvey (W. H., M.D.).— A manual of the British Algae, 8vo. London, 1841. Hassall (Arthur H.). — A history of the British Freshwater Algae (including descriptions of the Diatomaceae and Desmidiaceae), with upwards nil'.LIOGRAPHV. 117 of 150 plates, illustrating the various species. Vol. I., Text. Vol. II., Plates, 8vo. London, 1S44. A microscopic examination of the water supplied to the Inhabitants of London, 8vo. London, 1850. Hausler (Rudolf). — Die Diatomeen des London clay. Bot. Zeit. Leipzig (1881), xxxiv. col. 720-723. Hodgson (Miss E.). — On a deposit containing Diatomaceae, &c, in the iron-ore mines near Ulverstone, 8vo. Geol. Soc. Jour. (1863), xix., pp. 19-31. Hutton (Captain F. W.). — On the discovery of Arachnoidiscus ornatus and A. Ekienbergii at Malahide, Co. Dublin, 3 figs. Dubl. Mic. CI. lourn. Proc. (1865), i., p. 4; Q.J.M.S. (1865), v., p. 132. Jeffreys (John Gwyn). —Report on a dredging among the Hebrides. A. and M.N. H. (1866), xviii., Ser. 3, p. 393. Jenner (Edward).— Flora of Tunbridge Wells, 8vo. London, 1845. Karop (G. C.) and Morland (H.). — The Loch Kinnord and Skye Diatomaceous deposits, with hints on cleaning refractory material. J.Q.M.C. (1877), Ser. 2, hi., pp. 92-3. Kitton (Fred.). — Fauna and flora of Norfolk, Pt. VII. Diatomacese being a list of the Diatomaceae occurring at Norfolk. Norf. and Norw. Nat. Hist. Soc, Tr. (1875), »"•» PP- 33<>354- Discovery of Diatoms in the London clay ; references thereto by Grunow. Bot. Centralbl. (1880), i., p. 353. Fauna and flora of Norfolk Diatomaceae. Norf. and Norw. Nat. Hist. Soc, Tr. (1884), iii., pp. 754-770. Asteromphalus living on the Teignmouth coast. J.R.M.S. (1885), p. 3S0. Lankester (Dr. Edwin). — On a white incrustation on stones, from the bed of the River Annan. Linn. Soc, Proc. (1840), pp. 81-S2 ; M.J. (1841), i., pp. 40-41. Lankester (Dr. Edwin) and Redfern (Dr. Peter). — Report made to the Directors of the London (Watford) Spring Water Company on the results of microscopical examinations of the organic matters and solid contents of waters supplied from the Thames and other sources, 8vo. London, 1852. Macadam (Prof. William Ivison). — On Diatomaceous deposits in Scotland. Mineral Mag. (1884), vi., pp. 87-9; J.R.M.S. (1885), p. 287. Note on the presence of certain diatoms in a towi water supply. Edin. Roy. Phys. Soc Proc. (1S85), pp. 483-5 ; J.R.M.S. (c886), p. 291. [l8 BIBLIOGRAPHY. On the analysis of a sample of a white deposit from the peat of Aberdeen- shire. Edin. Geol. Soc. Tr. (1803), pp. 207-216. On the results of the Analyses of Diatomaceous deposits from the peat of Kinnord, Ordie, Drum and Blackmoss, Aberdeenshire. Edin. Geol. Soc. Trans. (1883), iv., pi. 3, pp. 277-2S3. On some new localities for the mineral diatomite, with notes on the chemical composition of the specimens exhibited. Mineral Mag. and Jr. Min. Soc. (1886), vii., pp. 30-34. Marquand (Ernest D.). — Desmids and diatoms of West Cornwall. Penzance Nat. Hist. Soc. Tr., No. 272, 8vo. Plymouth, 1882-3. Norman (George). — List of Diatomacea? occurring in the neighbour- hood of Hull. T.M.S. (i860), viii., pp. 59-71, 156-168. List of Diatomace?e occurring in the neighbourhood of Hull. Ed. 2nd, 8vo. Hull, 1865. Nowell (B. J.). — On the Menai Straits as a locality for the collection of Diatomacece. Q.J. M.S. (1858), vi., p. 122. Okeden (Fitzmaurice). — On the deep Diatomaceous deposits of the mud of Milford Haven and other localities. Q.J. M.S. (1855), hi., p. 26. On the Diatomacere of South Wales. T.M.S., (1859) vi., p. 87. O'Meara (Rev. Eugene). — Contributions to a catalogue of Diatomacea? of County Dublin, species from Malahide and Portsmouth. London, 1858. On the occurrence of recent diatoms in the lower territories of Hampshire. Dublin Geol. Soc. Trans. (1857-60), viii., pp. 105-6; Nat. Hist. Review, London (1859), vi. (Proc), pp. 68-9. Diatoms from the surface of a lake near Seaforde, Co. Down. May, 1865. Q.J.M.S. (1866), vi., p. 273. On Diatoms gathered at Rostrevor, Co. Down. Q.J.M.S. (1867), vii., p. 85. On Diatoms dredged by Dr. Wright off the Arran Islands. Q.J.M.S. (1857), vii., p. 113. On some new and rare Diatomaceae from the West Coast of Ireland. Q.J.M.S. (1867), vii, p. 113. New diatoms discovered by Dr. E. Percival Wright, off Arran Islands. Q.J.M.S. (1867), vii., p. 232. Notice of Plychodiscus Hneatus, a new genus and species of Diatoms from Arran, QJ.M.S. (1867), vii., p. 233. BIBLIOGRAPHY. 119 On new forms of Diatomaceae from dredgings off the Arran Islands, Co. Galway. Two series, i plate. Q.J. M.S. (1867), vii., p. 245 ; ser. III. QJ.M.S. (1869), ix., p. 15c, pi. XII. Notice of a new Tricer'aHum from Arran and a 5-sided form of Amfihitetras antedihiviana. QJ.M.S. (1867), vii., p. 298. Notice of a new Pinnularia from Arran. QJ.M.S. (1867), vii., p. 298. Report of the Irish Diatomaceae, pt. I. (all published), 9 plates. Roy. Ir. Ac. Sci. Proc, Dublin (1876), ii., Sec. 2, and thereon, F. Kitton, Sci. Gos. (1S76), xii. List of Diatomaceae found in the Counties of Dublin and Wicklow. Roy. Ir. Ac. Sci. Proc, Dublin (1878), i., p. 259. Parsons (Frederick A.). — List of objects (including diatoms) found on the excursion to the gardens of the Royal Botanical Society of London. J.Q.M.C. (1886), iii., Ser. 2, p. 31. Pearcey (Frederick G.).— Investigations on the food of the herring, with additions to the marine fauna of the Shetland Islands, with some re- marks on diatoms. Roy. Phys. Soc, Edin., Proc. (1874-85), viii., pi. II. , pp. 391-400. Petit (Paul). — Decouverte des Diatome'es dans l'argile de Londres. Brebissonia (1880), ii., p. 195. Phillips (John). — On the remains of microscopic animals in the rocks of Yorkshire. West Riding, York, Geol. and Polytech. Soc. (1842- 1846), ii., pp. 274-284. Pooley (Charles). ■ — The Diatomaceae of Weston-super-Mare. London, 1863. R. (J. M.), of Islington. — List of Diatoms found in fresh water and brackish ditches in the parish of Milton-next-Gravesend, and on the north side of the Serpentine, Hyde Park. QJ.M.S. (1853), i., P- 3°5- The same from the New River near the City Road, and from Trafalgar Square. QJ.M.S. (1853), i., p. 231. Ralfs (John). — On the Diatomaceae. Ann. Nat. Hist. (1843), xi., pp. 447-457; xii-, PP. 104-111. On the British Diatomaceae. Ann. Nat. Hist. (1843), xii., pp. 270-276, 346-352 ; (!845)> xvi-> PP-, 109-112. On the British species of Grammonema and Eunotia. Ann. Nat. Hist. (1844), xiii., pp. 457-461. 120 BIBLIOGRAPHY. On the British species of Achnanthes. Ann. Nat. Hist. (1844), xiii., pp. 489-493. On the British species of Meridion and Gomphonema, 1 plate. Edin. Bot. Soc. Tr., (1846), ii., p. 47. On some British Diatomaceae, 2 plates. Edin. Bot. Soc. Tr., (1S4.6), ii., p. 171. Ransom (Francis). — Diatoms, their nature and habits. Trans. Herts Nat. Hist. Soc. (1884), III., p. 197-206. Rattray (John). — A Diatomaceous deposit from North Tolstoa, Lewis, 1 plate. Edin. Ry. Soc. Trans. (1888), xxiii., p. 419. Robinson (Isaac). — The diatomaceae, with special reference to species found in the neighbourhood of Hertford. Hert. Nat. Hist. Soc. Tr. (1884), hi., p. 1. Observations on Diatomaceae from the neighbourhood of Hertford. Hert. Nat. Hist. Soc. Trans. (1887), iv., p. 196-200. Roper (F. C. S.).— Some observations on the Diatomaceae of the Thames. T.M.S. (1854), ii., n.s., pi. VI., pp. 67-80. On three new British Species of Diatomaceae. Q.J. M.S. (1854) ii., pp. 283-4. Notes on some new species and varieties of British Marine Diatomaceae. Q.J. M.S. (1858), vi., pi. III., pp. 17-26. List of Diatomaceae found near Eastbourne in Nat. Hist, of East- bourne, publ. by the Eastbourne Nat. Hist. Soc, p. 21. 1873. ^s0 m Chambers' Handbook of Eastbourne. Shrubsole (W. H.). — On a new diatom from the estuary of the Thames. J.Q.M.C. (1891), iv., Ser. 2, pp. 259-262. Shrubsole (W. H.) and Kitton (F.). — The diatoms of the London Clay, with alist of species and remarks by F. Kitton. 1 plate. J.R.M.S., (1881), i., Ser. 2, pp. 381-387, and thereon Grunow Bot. Centr. (1881), viii., p. 100. See Nature, June 9th, 1887. Smith (Rev. Wm.). — Synopsis of the British Diatomaceae, with remarks on their structure, functions, and distribution, and instructions for collecting and preserving specimens. 2 Vols., 69 plates, by Tuffen West. 8vo. London, 1853 and 1856. On deposits of diatomaceous earth found on the shores of Lough Mourne, Co. Antrim, with a record of species living in the waters of the Lake. A. and M.N.H. (1850), v., pp. 121-125. Notes on the Diatomaceae, with description of British species included in the genera Campylodiscus, Surire//a, Cymatopkura, 3 plates. A. and M. N. H, (185 1), vii., pp. 1-14. BIBLIOGRAPHY. 121 Notes on the Diatomaceae, with descriptions of British species included in the genus Pknrosi^ma, 2 plates. A. and M. N. H. (1852), vii., pp. 1-12. List of British Diatomaceae in the collection of the British Museum, i2mo. London, 1859. Sollitt (J. D.) and Harrison (R.).— On the Diatomaceae found in the vicinity of Hull. Q.J. M.S. (1854), ii., p. 61. Stolterfoth (H. W.). — List of Diatomaceae found in Chester District and Cwm Bychan. Chester Soc. Nat. Sc. Proc. (1878), p. 28. On a new species of the genus Eucampia (E. striata). J.R.M.S. (1879), »•> PP- 835-6- On the Diatomaceae in the Llyn Arenig Bach deposit. J.R.M.S., (1880), iii., n.s., pp. 913— 915- 2 n3s- Report on the Marine Diatomaceae of the Liverpool Marine Biological Committee's district. Second Rep. Fauna, Liverpool Bay. 8vo. Liver- pool, 1889. Stump (E. C). — On a deposit of Diatomaceous Earth at Loch Kinnord, Aberdeenshire. Manchester Mic. Soc. Tr., 1888. Toome Bridge Diatomaceous Deposit. — Belfast Nat. Field Club Proc. (1879-80) i. ser. 2, pp. 400-402. Trotter (R. de Bruce).— The Diatoms of the Tay. Perths. Soc. Nat. Sc. Proc. (1884-5), '•> pt- 5- PP- I92"3 \ (1885-6) pt. vi., pp. 223-5. West (William). — The fresh water Algae of North Yorkshire. Jr. of Bot. (1889), xxvii., p. 289. The fresh water Algae of North Wales. J.R.M.S. (1890), p. 300. A contribution to the fresh water Akae of West Ireland. Linn. Soc. Jr. (1892), xxix., pp. 103-216, 7 pi. Table of Names of Authors and Collectors cited. C. Ag. C. Agard. Mar. Marissal. Bell. Belleroche. Math. Mathieu. Breb. De Br^bisbon. Meneg. Meneghini. Cleve. Cleve. Naeg. Naegeli. Deby. Deby. Petit (Ch.). Petit (Charles). Del. Delogne. Petit (P.). Petit (Paul). Ehr. Ehrenberg. Rabh. Rabenhorst. Gaut. Gamier. Schum. Schumann. Greg. Gregory. A. Schm. A. Schmidt. Grev. Greville. W. Sm. W. Smith. Grun. Grunow. Thw. Thwaites. Hantzsch. Hantzsch. V. d. Broeck. Van den Broeck Heib. Heiberg. V. d. Born. Van den Born. Jan. lanisch. H. Vanh. or H. V. H. Van Heurck. Kickx. Kickx. Verb. Verbeeck. Kiitz. Kiitzing. West. Westendorp. 122 MEASUREMENT. Unit of Measurement. I have adopted in this work a hundredth part of a millimetre (o'oimm.), as the unit of measurement. I believe it to be the only convenient measure for organisms, whose size is so variable, that their maximum is often double their minimum size, and of which a con- siderable number are so large that if the mikron is used, too high a number (generally reaching into hundreds) has to be quoted. We mark this unit by three letters, c.d.m. (centiemes de millimetre). One c.d.m. = '0003937 English inch= io/j. (mikrons). End of Introduction. DESCRIPTION OF GENERA AND SPECIES. DlATOMACEzE. Unicellular algae consisting of a frustule or silicious bivalve box, pseudo-unicellular, externally covered with a more or less apparent mucous envelope (called coleoderm), containing in the interior of the valves a cellular membrane enclosing a brownish yellow colouring matter (called endochrome). a nucleus, some oil globules and colourless protoplasm. Diatoms multiply by gemmiparous self-division and are reproduced by conjugation. The family of Diatomaceads divided into three sub-families: i. Raphidieae having a true raphe on at least one of the two valves. 2. Pseudo-Raphidieae having, on at least one of the valves, a blank space, simulating a raphe, and never furnished with either teeth, awns, spines, or processes. 3. Crypto-Raphidiese never possessing either a true raphe or a pseudo-raphe on the valves ; generally circular, sub-circular or angular in form, and frequently furnished with processes, teeth, spines, or awns. 124 CYMBELLE.E. SUB-FAMILY I. — RAPHIDIE.E. Frustules mostly bacillar in valve view, sometimes broadly oval, always with a distinct raphe and nodules on one or both valves. Central nodule rarely absent or obscure ; valves simple or complex. Raphe generally prominent in valve view, occasionally in girdle view, especially when constricted, wTith nodules at the constrictions. Frustules always without teeth, spines, awns, or processes. ANALYSIS OF TRIBES. Valves alike Valves unlike f Valves more or less arcuate or cymbiform, not symmetri- cally divided by the raphe .... f Valves symmetrical ; central nodule either equally distant from ends or absent, or rudimentary or divided .... Valves symmetri- cally divided by the raphe . I r Valves cuneate Valves cuneate n o t | Valves asymmetrical with apices of L unequal breadth (valves cuneate) Frustules genuflexed, nodule or stauros on one valve only, usually on the conca/e margin (at the constriction) valves rarely broadly oval .... Frustules with a central nodule on only one valve, valves generally broadly oval, rarely bent, never genuflexed Cymbelleee. Naviculeae. Gomphonemese. Gomphonemeee. Achnantheae. Cocconideae. Tribe i. — Cymbelle/E. Connecting membrane highly developed on the dorsal side, so that the two valves are seen at the same time and nearly flat ; central nodule very apparent, rounded or changed into a stauros, raphe without keel . Frustules with connecting membrane very broad, often \ Frustule constricted as Amphora, but the raphe furnished longitudinally plicate, striate, or punctate I with a keel Valve very asymmetrical, with dorsal and ventral parts situated in different planes and the raphe elevated on a very projecting keel .... Amphora. Amphoropsis. Auricula. Frustules with f connecting membrane nar- ,, , row and neither \ , , longitudinally punctate nor plicate . . t without f Frustules free or stipitate ; terminal nodules near the apices, raphe more or less arcuate Frustules often enclosed in tubes ; terminal nodules very distant from apices ; raphe quite straight Cymbella. Encyonema. AMPHORA. I25 GENUS I.— AMPHORA EHR, 1831. I bis 1 Frustules generally free, solitary, oval, oblong, elliptic oval or sub-quadrangular, often inflated or constricted in the girdle view. Valves cymbifurm, with central nodule marginal or sub-marginal, often dilated into a stauros, raphe often inflated. Connecting zone often longitudinally striate, plicate, or punctate. Endochrome formed by a single layer, the middle of which rests on the dorsal, connecting zone, and ra covers over the two adjacent valves and the other side of the zone, in the middle of which is found the line of separation. A large number of Amphora are " complex." Those are so named whose connecting zone contains a more or less considerable number of cuneate seg- ments which have been, somewhat justly, compared to slices of melon. These segments have sometimes a structure or striation analogous to that o the exterior segments (valves) but have neither raphe nor nodules ; at other times however the striation of the interior segments is different. The genus Amphora is one of the most difficult genera of diatoms, and it is also one of the most extensive, as authors have placed in it more than 200 species. Prof. H. L. Smith was the first to elucidate the structure of Amphora by demonstrating that the genus originated from Cymbella by the unequal development of the two sides of the connecting zone. Figure 24 a is a diagrammatic section of an Amphora showing at the same time the disposition of the layer of endochrome. In the arrangement, in this Work, of the genus Amphora, the classifi- cation of Prof. Cleve has been followed. The sub-genera and the list of species are given in accordance with the manuscript documents kindly lent by the learned Professor. 4j Fig. 24. a Diagrammatic section of Amphora. b Amphora ajfinis, valve view. c Amphora ovalis, girdle view. V» 126 AMPHORA. Analysis of Groups. Puncta rather coarse, very distinct, forming transverse strife and undulating longitudinal lines . Connecting -[ zone not plicate Connecting zone plicate Puncta not forming longitu- dinal lines Ventral portion of valve broad, stria; finely punctate on both parts of the valve Ventral portion of valve very narrow, strife not distinctly beaded Coarse puncta, very distinct, arranged in straight trans- verse and longitudinal lines .... f Valve with ventral portion narrow, apices generally rostrate-capitate and recurved, beads forming undulating longitudinal lines ...... Valve with central port'on smooth, furnished with a longitudinal ridge .... 1 Puncta not forming straight ■{ ongitu- dinal lines Not as above Ventral portion striate. Ventral portion rather broad, the two parts with identical stria- tion, raphe with bran- ches divergent from the central nodule . Ventral portion very narrow, with finer striation than that of the dorsal portion ; raphe straight, near the margin ; central nodule often stauro- form . Subg. i. Amphora. Subg. 2. Psaniinamphora Subg. 3. Cyrnbampliora. Subg. 4. Diplamphora. Subg. 5. Halamphora. Subg. 6. Calampliora. Subg. 7. Amblyamphora. Subg. 8. Oxyamphora. A. — Sutural zone not plicate. GROUP i. Amphora — Ventral and dorsal portions of the valve generally furnished with a longitudinal line (a rib or narrow area). Beads rather coarse, forming at the same time transverse striae and undulating longitudinal lines. (Type: A. ovalis). Non- marine Marine forms ANALYSIS OF SPECIES. f Fresh water ; striae robust in the type form ; pseudo-stauros very distinct ........ :orms. • Humid places (walls, etc.) Raphe slightly incurved, stauros spurious Frustule not subrectangu- lar, apices obtuse or truncate t. Raphe concave, no spurious stauros Striae fine, resolvable A. ovalis A. Normanii. A. perpmilla. A. marina. A. Fusio. 14 to 16 striae in 1 c.d.m. . I Striae strong, irresolvable / Raphe with ventral portion com- About 10 striae J P^ely striated . . A. robusta. in 1 c.d.m. . | Raphe with ventral portion I, v having only some lines of dots A. Proteus. Frustule with acute or subacute apices, dorsal margin of valve plicate longitudinally . . . . . .A. dubia. Frustule subquadrangular, striae extending throughout the ventral portion of the valve . . . . . . .A. arenicola. AMPHORA. 127 A. OValis Kutz. (Bac. p. 107, pi. 5, fig. 35 and 39; H.V.H. Ati., pi. 1 f. 1* Type No. 1) plate 1, fig. 15. Frustule oval, very inflated at the median portion, then slightly atten- uate ; apices broadly truncate. Valves arcuate at dorsal margin, concave at internal margin ; raphe inflexed ; striae strongly marked with coarse puncta from 10 to n in 1 c.d.m. without stauroneiform blank space. Length, 5 to 7 c.d.m. Fresh water. Common everywhere. /3 gracilis (A. gracilis E. Verb. p. 122, n. 11, pi. III. 1, f. 43 — H.V.H. Atl., pi. i,' f. 3*) plate 1, fig. 16. Considerably narrower and more slender in all parts than the pre- ceding ; apices rounded, subacute ; raphe very inflexed. Mixed with the preceding. Louvain. y. affinis Kutz. (Bac, p. 107, pi. 30, f. 66 ; A. abbreviaia Blrisch ; H.V.H. Atl., pi. 1, f. 2*; Type No. 2) plate 1, fig. 17. Frustule oval, with apices slightly tapering ; striae rather finer (about 12 in 1 c.d.m.) leaving a stauro-form blank space very distinct on the dorsal side. Length, 3 c.d.m. Fresh and slightly brackish water. Blankenberghe(pure gathering). Louvain (H.V.H.) Ardenne Liegeoise (De Wild). Free or mixed with the preceding. England (Norman, W. Sm.). forma minor (A. Pediculus major Grun ; H.V.H. Atl., pi. 1, f. 4, 5*) plate 1, fig. 18. Smaller, about 3 c.d 111. in length; striae fine, about 16 in -oi c.d.m. Louvain, etc. 8. Pediculus Kutz. (A. Pediculus (Kiitz.) Grun. — Cymbella Pediculus Kutz. Bac, p. 80, pi. 5, f. VIIL, and pi. 6, f. VII. A. minutissima, IV. Sui., S.B.D. i., p. 20, pi. II., t. 30. H.V.H. Atl, pi. 1, f. 6, 7*; Type No. 3) plate 1, fig. 19. Frustule small, with apices slightly narrowed; pseudo-stauros very distinct; raphe more or less concave; striae 16 in 1 c.d.m.; length about 2 c.d.m. Generally parasitic on other diatoms, and especially on Nitzschia Sigmoidea. Common. Antwerp, Louvain, Blankenberghe (H.V.H. ) Aid. Li£g. (De Wild.), etc. England (W. Sm., Norman, Stolterfoth). forma minor, Grun. (H.V.H. Atl., pi. 1, f. 8*), plate 1, fig. 20. Still smaller, about 1*5 c.d.m. in length ; about 20 striae in 1 c.d.m. forma exilis, Grun. (H.V.H. Atl., pi. 1, f. 9, 10*), plate 1, fig. 21. Small, very narrow, length from 1*5 c.d.m., striae about 20 in 1 c.d.m. A. perpusilla Grun (h.v.h. Atl., pi. i, f. n*; Type, No. 4), plate 1, fig. 12. 128 AMPHORA. Very small. Frustule oblong or subglobose, rather truncate at apices. Valve very convex at dorsal margin, straight at ventral margin ; raphe straight, scarcely concave, spurious stauros just visible ; striae very delicate, numbering from 9 to 10 in 1 c.cl.m. ; length less than 1 c.d.m. Moist wa'l at Botanical Gardens, Brussels, associated with A. Normanii (Del). This form should probably be referred to A. ovalis var Pediculus. A. Normanii Rabenh. (Fi. Eur. Aig., p. 88. A. humkola Gntn in H.V.H. Atl., pi. i, f. 12*; Type No. 5) plate 1, fig. 4. Frustule elliptic with apices slightly rostrate-truncate. Valve with raphe slightly inflexed, showing a stauro-form blank space ; apices rostrate-capitate; striae fine, punctate, from 16 to 18 in 1 c.d.m. at the dorsal portion of valve, very fine, about 24 in 'or at ventral m 11 gin. Length, 2.5 to 3 c.d.m. On a moist wall at Botanical Gardens, Brussels (Del); Hull, England (Norman). A. dubia (Greg, 1857?) Ad. Schm, 1875 (At, pi. 27, f. 20-26* ; Clyde, p. 42, pi. 5, f. 76) ; plate 24, fig. 672. Frustule elliptic. Valve angularly plicate round a line uniting the two apices, so that when viewed from the apex it appears to consist of two laminae placed at an angle of 6o°. Valve with lunate outline, arcuate near the exterior, with the interior margin straight and apices acute. Axial area moderately broad on the dorsal side of the raphe. Ventral portion of the valve linear, narrow, wuhout striae and longitudinal line. Dorsal side with transverse striae robust, especially at the external portion. Striae 10 in r c.d.m., coarsely punctate ; 12 dots in 1 c.d.m. Sutural zone very narrow. Length of frustule 4 to 8 c.d.m. ; breadth, 1-5 to 2 c.d.m. Marine. — Coasts of Norway. There is no known species analogous to A. dubia (Cleve). A. Pusio Cleve (Syn. Nav. Diat., p. 102, pi. 3, f. 40*) ; plate 35, fig. 906. Frustule broadly elliptic with truncate apices. Raphe strongly bi-arcuate. Central nodule large. Axial and central areas indistinct. Ventral and dorsal sides with robust striae, about 14 in 1 c.d.m , not interrupted and not distinctly punctate Marine and brackish water. — Coasts of Sweden (CI. and Moll. Diat., No. 157). A. arenicola Grun. (in CI. and Moll. Diat., No. 310, sub A marina var arenico/a ; Cleve Syn. Nav. Diat., pi. 4, f. 19-20), plate 35, fig. 907. AMPHORA. 129 Frustule almost rectangular, three times longer than broad. Valve linear with apices broad, unilaterally rounded. Raphe gently bi-arcuate, distant from ventral side. Axial area indistinct on dorsal side. Central area absent or orbicular. Striae of dorsal side 10 to 14 in 1 c.d.m., coarsely punctate, not interrupted, with indistinct longitudinal line. Ventral side broad, with striae radiant, coarsely punctate, sometimes crossed by a narrow hyaline band. Length of frustule, 4 to 7 c.d.m. Breadth, 17 to 2-1 c.d.m. Breadth of valve, 1 c.d.m. Marine. — Coasts of Belgium and England (Cleve). Var. major A. Baltic Sea (CI). A. marina H. Van Heurck (h.v.h. Atl., pi. i, f. 16*; in Types Nos. 101 and 517), plate 1, fig. 14. Frustule oblong, very inflated at median part, infinitesimally attenuated as far as the apices which are truncate. Valves with dorsal margin very convex, and ventral margin slightly and almost regularly concave ; raphe well marked, inflexed at median part ; striae rather strongly punctated on dorsal side ; about 16 in 1 c.d.m., same number at ventral margin. Length, 4 to 5 c.d.m. Marine.— Shores of North Sea: England (W. Sm.), France (Grun. , Brdb.), Belgium: Scheldt. (H. Van Hk. ), and probably on all shores of North Sea. According to Prof. Cleve this form should be recorded as having been first described by me, and the A. marina of Wm. Smith treated as only a form of A. Proteus. A. robusta Greg. (Diat. of Clyde, p. 44, pi. 5, f. 79; Ad. S. Atl, pi. 27, f. 40-41*); plate 24, f. 670. Frustule broadly oval with truncate or sub-truncate apices. Valve arcuate, with apices obtuse, raphe very inflexed, central nodule large, surrounded by a blank space slightly stauroform. Ventral margin concave. Ventral part of valve completely striated, striae with coarse puncta, 7 to 8 in 1 c.d.m. Sutural zone completely smooth. Length, 8 to n c.d.m. Marine,— Scotland (Gregory) and Shores of North Sea; Belgium: Scheldt (H. Van Hk.) A. Proteus Greg. (Diat. of Clyde, p. 46, pi. 5, f. 81; Ad. Sch. Atl., pi. 27, f. 2-3; 5-6*); plate 24, fig. 671. Frustule elliptic, with truncate apices. Valve with dorsal margin arcuate, ventral margin concave, apices obtuse. Raphe very inflexed ; central nodule K 130 AMPHORA. rather large, often furnished with a stauroform blank space. Ventral part of valve having only a few rows of dots. Striae very distinct with robust puncta ; 8 to 10 in 1 cd.m. Length very variable, from 7 to 15 c.d.m. Breadth, from 4 to 6 c.d.m. Marine. — Scotland (Greg.), England, Belgium! Germany! Norway ! etc. 2. Psammamphora CI. — Ventral part rather broad. The two parts finely puncto-striated. Puncta not forming longitudinal lines. (Type form : A. arenaria). ANALYSIS OF SPECIES. Frustule with outer margins slightly introrlexed, valves furnished with a stauros ........ A. ocellata. Frustule with outer margins slightly gibbous, valves without stauros . A. arenaria. A. OCellata Donk (Q.J.M.S., i86i, p. n, pi. i, f. nb; H.V.H. Atl, pi. 1, f. 26*); plate 1, fig. 3. Frustule quadrangular, with rounded apices and outer margins slightly introflexed. Valve with raphe infinitesimally incurved ; striae very fine and very delicate. Length, 6 to 9 c.d.m. Marine. — Found in washings of mussels and in the residue of a washing of sand from the beach at Blankenberghe. England ; Ireland ; France. A. arenaria Donk. (T.M.S., 1853, p. 31, pi. 3, f. 16; Ad. Sch. Atl., pi. 40, f. 8-10*) ; plate 24, fig. 673. Frustule hyaline, subquadrangular ; apices rounded, truncate ; median portion often slightly gibbous ; raphe very inflexed. Valve broad, arcuate ; apices very obtuse ; terminal nodules recurved near the outer margin, rather broad and very elongated. Ventral portion of the valve very broad, finely puncto-striate, as is also the dorsal portion. Length, 10 to 12 c.d.m. Marine.— England (Norman) : Ireland (O'Meara) ; Shores of the North Sea. 3. Cymbamphora CI. — Striae not forming longitudinal lines, and not distinctly beaded. Ventral portion of valve very narrow. (Type form : A. angusta). A. angusta Greg. (Diat. of Clyde, p. 38, pi. 4, f. 66*), plate 24, fig. 674. Frustule small, linear, elliptic, narrow, apices truncate. Ventral margin of valve straight, raphe very inflexed. Part of valve narrow, stria? very delicate, not distinctly beaded, about 17 in i c.d.m. Sutural zone very narrow. Marine. — Scotland (Greg.) : Shores of North Sea. AMPHORA. 131 B. — Siditral Zone plicate. 4. Diplamphora CI. — Dorsal portion and often also ventral portion with puncta forming longitudinal lines. Puncta coarse. (Type form : A. crassa). ANALYSIS OF SPECIES. f Valve with double structure ; furnished with costre Valve without I between which are found rudimentary beads . A. crassa. an ala . | Valve with structure simple, furnished with three longi- ^ tudinal curved lines, dividing the valve into two zones A. Grevilleana. 1. Valve furnished with an ala emanating from the dorsal portion . . A. alata. A. crassa Greg. (T.M.S., 1857, p. 72, pi. 1, f. 35 ; Diat. of Clyde, p. 52, pi. 6, f. 94a*) ; plate 24, fig. 675. Frustule rectangular, elliptic, with rounded apices. Ventral margin and raphe strongly inflexed at the median portion. Valve with dorsal margin arcuate. Ventral margin concave, inflexed at the median portion. Striae 5 in 1 e.d.m., formed of coarse puncta?, arranged in transverse and longitudinal lines. Connecting zone showing lines of coarse punctae, showing the margins of internal segments. Length 8 to 10 c.d.m. Marine. — Shores of the North Sea : Scotland (Greg.), England (Norm.), Ireland (O'Meara), Finmark (Cleve), etc. * Note. — The striae of A. crassa have hitherto been inaccurately described by authors. In reality the dorsal margin of the valve shows two rows of strong costa; and at the bottom of the intercostal spaces is a row of delicate puncta. A. Grevilleana Greg, (t.m.s., 1857, p. 73, pi. 1, f. 36; Diat. of Clyde, p. 50, pi. 5, f. 89 ; Ad. Schm. Atl., pi. 25, f. 41*) ; plate 24, fig. 676. Frustule almost oval, with apices slightly truncate. Valves marked with three longitudinal curved lines, dividing the valve into two compartments; apices slightly diminuo-rostrate ; dorsal margin infimtesimally arcuate, ventral margin and raphe inflexed. Transverse striae strong, moniliform, n in 1 c.d.m. Sutural zone showing 7 to 8 juxtaposed segments. Length 12 to 13 c.d.m. Marine.— Scotland (Greg.) and various Shores of the North Sea. A. alata Per. (Diat. Baie de Villefranche, p. 41, pi. 2, f. n*); plate 24, fig. 677. A form distinctly differentiated by the presence of a membranaceous ala, emanating from dorsal portion of the valve. Marine.— North Sea (Cleve). !32 AMPHORA. 5. Halamphora CI. — Longitudinal lines absent. Ventral portion of the valve narrow. Valve with apices generally capitate and recurved. Beads distinctly arranged in transverse striae and in series of longitudinal undulations. f Fr 0. E o f Striae with puncta some- what indistinct, very delicate ■a c to J ANALYSIS OF SPECIES. istules complex, beads resolving into a mass of fine puncta ..... f Frustules with external margins undulated ....... Transverse strire almost invisible, longitudinal conspicuous Transverse strire fine, median more robust f Sutural zone abruptly dilated at the apices 1 Sutural ( Frustule elliptic, with sutural zone lanceolate I zone not < I dilated. ( Frustule suboval, with apices rostrate-capitate f Frustules more or less constricted - r Strire with distinct puncta. Frustules robust. Frustules delicate. in the mid- dle. Constriction slight, frustule broad, sutural zone with numerous folds ........ I L I Frustules not con- stricted. Constriction considerable, frustule narrow, sutural zone without folds ........ Connecting zone with very numerous folds Puncta robust, frustule rostrate-capitate Sutural zone not -J plicate. A. Eunotia. A. Sarniensis. A. coffeaeformis. A. veneta. A. commutata. A. cymbifera. A. rostrata. A. angularis. A. binodis. A. inflexa. A. turgida. Puncta delicate or resolvable - with difficulty. f Transverse strire conspic- uous, about 9 in 1 c.d.m. ; frustule very long, about 8-9 c.d.m. A. Ergadensis. Ranhe I Striae conspicuous, about straight "' I2 'n l c-^m- > frustule 0 short, about 5 c.d.m. . A. macilenta. ! Strire . delicate, finely punctate, about 13-14 in 1 c.d.m. ; frustule short, about 5 c.d.m. . A. acutiuscula. Raphe curved, frustule very short, about 3 — 5 c.d.m. ; striae very deli- cate, about 19 in 1 c.d.m. . . A. salina. A. commutata Grun. ! (A. affinis W. Sm. S.B.D. L, p. 19, pi. 2, f. 27, not Kutz ! — W. Sm. prep. No. 27 !— H.V.H. Atl., pi. i.,f. 14* ; Type No. 7) plate 1, fig. 13. Frustule oblong with rounded or truncate apices ; connecting zone abruptly inflated towards the apex, marked with several fine longitudinal striae. Valves with dorsal margin straight at median part, then abruptly attenuate and forming an obtuse point in consequence of a corresponding constriction in the ventral margin ; raphe strongly inflexed ; striae, robust on dorsal side, 9 in 1 c.d.m. ; fine and marginal on ventral side, 15 in 1 c.d.m. Length, 5 to 6 c.d.m. Brackish waters — Antwerp, Blankenberghe, Heyst, Ostend (H.V.H.) ; England (W. Sm ! Stolterfoth.) ; Scotland (Greg); France; Germany! Norway! and probably throughout the shores of the North Sea, \ AMPHORA. I33 A cymbifera Greg. (Diat. of Clyde, p. 54, pi. 6, f. 97. Ad. Sch. Atl., pi. 25, f. 13, 17-19* ; pi- 26> f- 33) Plate 24, fig. 678. Frustule elliptic, with produced truncate apices ; valves narrow, arcuate with rostrate-capitate apices; ventral margin and raphe almost straight ; striae radiant, robust, 9-12 in 1 c.d.m. Sutural . zona elliptic. Length, very variable, from 5 to io c.d.m. Marine.— England, Scotland, Ireland, Denmark, Norway, etc. A. rostrata W. Sm. (s.B.D. i., p. 20, pi. 30, f. 253*) plate 24, fig. 679. Frustules inflated, sub-oval with apices rostrate-truncate showing longitudinal costae marked with a double row of puncta. Valves arcuate semi-lunar with apices capitate : striae robust, 6 to 7 in 1 c.d.m. Marine. — England (W. Sm. Norman), Scotland (Greg.), Ireland (O'Meara). A. angularis Greg. (Q.J.M.S., 1855, p. 39, pi. 4> f. 6 ; h.v.h. Atl., pi. 1, f. 21*, Type No. 12) plate 1, fig. 8. Frustule panduriform with apices tapering, broadly truncate, connecting zone with fine transverse striae, interrupted by numerous pleats. Valves with dorsal margin constricted in the middle, apices tapering, acuminate, raphe infinitesimally inflexed ; striae punctate, about 18 in 1 c.d.m. Length, 4 to 5 c.d.m. Var. hybrida Grun. (In H.V.H. 's Type, No. 12). Valves with constriction only slightly if at all marked, showing a longitudinal line in the convex part. Var. lyrata (A. lyrala Gres,. Diat. of Clyde, p. 48, pi. 5, fig. 82, H.V.H. Atl., pi. 1, fig. 22* ; in Type No. 12) plate 1, fig. 9. Differing from the type-form in being shorter (about 3 c.d.m.) and its median constriction being less pronounced, which, when inadequately resolved, slightly resembles a stauros. Brackish waters, — The type form, and varieties mixed together at Blankenberghe and Antwerp. Scotland, Ireland, Norway. A. macilenta Greg. (Diat. of Clyde, p. 38, pi. 4, f. 65*) plate 24, fig. 680. Resembling A. salina. — Frustules elliptic, long, narrow, with apices pro- duced, tapering ; valves very delicate, arcuate on dorsal side, ventral margin straight. Raphe very distinct. Striae parallel, rather robust, 12 in 1 c.d.m. Sutural zone very narrow. Length, 4 to 5 c.d.m. Marine.— Scotland (Gregory) ; North Sea. This species is quite unknown to me, and the very poor figure given by Gregory makes it impossible to recognize it. 134 AMPHORA. A. acutiuscula Kutz. (Baa, p. 108; H.V.H. Atl., pi. i, f. 13* in Type No. 261), plate 1, fig. 5. Frustules elliptic or elliptic-lanceolate, with apices slightly rostrate, truncate. Valve with dorsal margin arcuate, ventral margin slightly inflated ; apices rostrate-capitate; raphe straight, striae with distinct puncta, 13 to 14 in 1 c.d.m. on dorsal side, 18 to 20 on ventral side. Length, about 5 c.d.m. Marine. — Blankenberghe ; North Sea. A. salina W. Sm. (s.B.D. L, p. 19, pi. 30, f. 251 ; H.V.H. Atl., pi. 1, f. 19*; Type No. 11), plate 1, fig. 6. Frustule elliptic-oblong with apices slightly produced, truncate. Valves with apices rostrate, slightly capitate ; dorsal margin arcuate, ventral margin straight or concave ; raphe concave with reference to the connecting zone ; striae fine, punctate, 18 to 21 in 1 c.d.m. on the dorsal side, 20 to 21 on ventral side. Length, 3 to 5 c.d.m. Brackish water. — Common at Antwerp, Blankenberghe, Heyst ; England ; Scotland ; Ireland ; Denmark ; and probably throughout the shores of the North Sea. ft minor. (A. borealis Kutz! Baa, p. 108, pi. 3, f. 18; H.V.H. Atl., pi. i, f. 20*), plate 1, fig. 7. Smaller and broader, with a not very pronounced beak. Slightly brackish water — Blankenberghe. A. coffeseformis Kiitz. ! (Baa, p. 108, pi. 5, f. 27 ; Ad. Sch. Atl., pi. 26, f. 56, 58, 59*) plate 24, fig. 681. General appearance resembling that of A. Salina, but frustules tapering infinitesimally to apices, which are generally very slightly produced. Valves with apices rostrate, very slightly capitate. Transverse stride excessively delicate and almost invisible. Longitudinal striae few but very distinct. Brackish and Marine. — Shores of North Sea A. veneta Kiitz. (Baa, p. 108, pi. 3, f. 25 ; H.V.H. Atl., pi. 1, f. 17*; Type No. 10) plate I, fig. 11. Frustule oblong-elliptic, with apices slightly truncate. Valves with dorsal margin convex, infinitesimally attenuate ; ventral margin flat or slightly concave ; raphe concave ; central nodule elongated ; striae fine, about 20 in t c.d.m., slightly more robust in median portion. Length, 2 to 3 c.d.m. Brackish water. — Blankenberghe, Antwerp. AMPHORA. 135 A. inflexa (Breb.) H. L. Sm. (in Lens, 1873, p. 78.) Under the name of Amphipleura inflexa, De Brebisson has described a rather singular diatom which he found on the coast of Normandy. In 1868, Eulenstein formed the genus Okedenia with this species, and in our " Types du synopsis " we distributed it under the name of Okedenia inflexa, Eul. After a careful study of this form, the result of which I communicated to Professor Cleve, the learned diatomographer thought that this diatom was simply an Amphora of the sub-genus Halamphora. Professor H. L. Smith had previously classed it among the Amphora ; I therefore place it here under the name of A. inflexa. No correct figure of this diatom having yet been published we give here. one of our photograms of it. Valves narrow, arcuate, with apices unilaterally capitate, recurved. Sutural zone very narrow on dorsal side, more or less developed on ventral side, and displaying a more or less considerable number of pleats. Raphe inflexed, quite on the margin of the frustule and scarcely visible. Central nodule very elongate and more or less rudimentary. Valve with puncta forming transverse striae (about 18 in 1 c.d.m.) and longitudinal lines. Connecting zone finely striate trans- Fig. 25.—^. versely, about 20 striae in 1 c.d.m. Length, 10 to 12 c.d.m. (Okedenia) inflexa. Breadth of valv6j mther jess than , c d m at the med;an portion. Breadth of frustule, 7 to 15 //. Marine.— North Sea : France (Breb !) ; England (W. Sm. !) A. Sarniensis Grev. (t.m.s. 1862, h\, n.s., p. 95, pi. 9, f. 12; Ad. Schm. Atl.,pl. 25, f. 80*), plate 24, fig. 682. Frustule constricted at the median portion, with bi-undulated lobes, apices truncate, produced. Striae about 12 in 1 c.d.m. Length, 4 to 5-5 c.d.m. Marine — Guernsey (Wallich). A. Ergadensis Greg. (Diat. of Clyde, p. 40, pi. 4, f. 71*), plate 24, fig. 683. Frustule elliptic lanceolate, with apices diminuate. sub-rostrate-truncate. Valves very narrow with raphe approximate to the ventral margin, which is flat ; dorsal margin regularly arcuate, extremely obtuse, somewhat prolonged- capitate. Transverse striae strong, with difficulty resolvable into puncta, 9 in 1 cd.m. Connecting zone showing 3 to 5 longitudinal rows of coarse puncta. Length, 8 to 9 c.d.m. ; breadth at the median portion, about 1*5 c.d.m. Marine— Lamlash Bay, Loch Fine (Scotland, Greg.) j -g AMPHORA. Gregory's figure is very bad and renders the diatom scarcely recognizable. My description is made from an example from the Balearic Islands, determined by Mr. Grunow. The same remark applies to the figure given in my plates. A. Eunotia Cleve (Diat. Arct. Sea, 1873, p. 21, pi. 3, f. 17*), plate 24, fig. 684. Frustule complex, oval, broadly truncate, raphe straight. Valves coarsely striate, with strise moniliform, about 6 in j c.d.m., consisting of very fine puncta, grouped, compact, about 9 in 1 c.d.m. Central nodule rounded, very distinct. Length, about 8 c.d.m. ; breadth, 5 c.d.m. North Sea ; Greenland ; Spitzbergen ; Finmark, etc. (Cleve). A. binodis Greg. (Diat. of Clyde, p. 38, pb 4, f. 67*), plate 24, tig. 686. Frustule linear-oblong, with apices attenuate-truncate, median portion constricted. Raphe fiexuous, bi-arcuate. Striae about 14 in i c.d.m. Length, about 4-5 c.d.m. ; breadth, 1-25 c.d.m. Marine— Coasts of Scotland (Greg.) ; England (Stolterfoth). A. turgida Greg. (Diat. of Clyde, p. 38, pi. 4, f. 63*), plate 24, fig. 685. Small, suborbicular-lanceolate, with apices rostrate, more or less capitate. Valves with dorsum very convex, venter flat, apices diminuate, rostrate, sub- capitate. Striae, 7 to 9 in 1 c.d.m., consisting of coarse puncta, somewhat distant and interrupted near the dorsal margin by a hyaline line, more or less conspicuous, following the outline of the valve. Length, 2-5 to 7 c.d.m. Breadth, 1-25 to 2 c.d.m. Maiine— Lamlash Bay ; Loch Fine (Scotland, Greg,) ; England (Stolterfoth). 6. Calamphora CI.— Ventral portion of valve smooth, furnished with a longitudinal line (or rib). Dorsal portion without rib and furnished with transverse striae, indistinctly punctate, or with costiform striae alternating with indistinct beads. (Type form : A. formosa CI.). A. limbata CI. and Grove. (Le Diatomiste i., p. 159), plate 35, fig. 908. Frustule rectangular, somewhat constricted in the middle, showing on each side a hyaline line which appears to come from the dorsal part. Valve narrow, linear with subcapitate apices and arcuate raphe ; dorsal portion striate, 8 strias in i c.d.m. ; ventral portion without striae, but with a longitudinal line. Connecting zone with 5-8 divisions, transversely striated, striae about 8.5 in 1 c.d.m. Length of frustule, 4-5 to 7.5 c.d.m. Breadth, 2 to 3.5 c.d.m. Marine — Grip (Norway, Cleve.) AMPHORA. 137 7. Amblyamphora CI. — Valves without longitudinal lines. Ventral portion rather large, with a structure similar to that of the dorsal portion or striae finely punctate. The branches of the median line diverge from the central nodule. (Type form : A. obtusa). ANALYSIS OF SPECIES. ( Strife very distinct, distant ..... A. spectabilis. ' Strife very delicate, indistinct, approximate . . .A. obtusa. A. spectabilis Greg. (Diat. of Clyde, p. J4, pi. 5, f. 80*), plate 24, fig. 687. Frustule linear or linear-oblong with apices rounded, sub-truncate. Valve with apices obtuse, ventral portion rather broad, raphe strongly inflexed, central nodule large. Stria; rather broad, distant, diminishing in breadth from the side of the raphe, 5 to 6 in 1 c.d.m. Length, 8 to 15 c.d.m. Marine and brackish water. — Coasts of the North Sea; England (Stolterfoth) ; Scotland (Greg.), etc. A. obtusa Greg. (T.M.S. 1857, v., p. 72, pi. 1, f. 34; Ad. Sch. Atl., pi. 40, f. 16-17*), plate 24, fig. 688. Frustule broadly linear-oblong with apices rounded, not truncate. Valves arcuate on dorsal side, almost straight on ventral side, with apices very obtuse. Raphe very inflexed with central and terminal nodules very large. Ventral portion broad, with striation identical with that of the dorsal portion, ventral margin slightly constricted near the apices. Stria; very delicate, approximate, indistinct, about 12 14 in 1 c.d.m. Sutural zone narrow. Length, 8 to 13 c.d.m. Breadth of valves, 1/5 to 2 c.d.m. Marine. — Coasts of the North Sea ; Scotland (Greg. !), etc. 8. Oxyamphora CI. — Valves without longitudinal lines. Ventral por- tion generally very narrow and with striation identical (not finer) with that of the dorsal portion. Raphe generally straight and approximate to margin. Nodule often stauroid. Striae punctate (Type form : A. acuta). ANALYSIS OF SPECIES. f Frustules with the outer margins more or less inflated at the median portion . . . . .A. ostrearia. Valve with ] r . , ... f RaPhe straight . A. acuta. stauros. { Frustule with outer margins -j Raphe gradually inflexed . A. laevis. not inflated. [ Raphe abruptly inflexed . . A. lsevissima. Frustule linear, elongate, subelliptic . . .A. bacillaris. f Frustule robust with striae robust, Valve with- j Frustule moniliform . . . .A. Arcus. out stauros. \ more or less J quadra ngu- j p t 1 f ^aphe straight . A. hyalina. I hyaline. "j Raphe inflexed . A. lineolata. 138 AMPHORA. A. bacillaris Greg. (Diat. of Clyde, p. 55, pi. 16, f. 100*), plate 24, fig. 689. Frustule linear, narrow, with apices slightly rounded, subacute. Valve with ventral portion narrow, striation finer than that of the dorsal portion. Raphe slightly inflexed. Connecting zone narrow on ventral side, very large on dorsal side of frustule and showing 7 or 8 narrow segments. Marine. — Scotland (Gregory). A. ArCUS Greg. (Diat. of Clyde, p. 50, pi. 13, f. 88*), plate 24, fig. 690. Frustule subquadrangular, with outer margins infinitesimally inflated as far as the central portion, with truncate apices. Valves narrow, with ventral margin infinitesimally arcuate, ventral margin and raphe inflexed, apices strongly rostrate, slightly capitate. Stripe robust, moniliform, 6 to 7 in 1 c.d.m., Sutural zone showing 16 to 17 robust bars formed by the ventral margins being approximate to juxtaposed segments. Length, 9 to 10 c.d.m. Breadth, up to 5 c.d.m. Marine. — England (W. Sm. Greg., Norman) ; Scotland (Greg). A. lineolata Ehr. {Navicula lineolata Ehr. Inf., p. 188, n. 250 pi. 14, f. 4 ; A. tenera, W. Sm., S.B.D., i., p. 20, pi. 30, f. 252, H.V.H., Atl. pi. 1, f. 23*; Type No. 6); plate 1, fig. 10. Frustule elliptic-oblong, inflated at the median portion, infinitesimally attenuate up to the apices which are slightly rounded. Valves with raphe considerably inflexed, with striae finely punctate, about 23 in 1 c.d.m. Connecting zone with very fine transverse strioe, interrupted by numerous longitudinal pleats. Length, 4 to 5 c.d.m. Fresh and brackish water. Blankenberghe ; England (W. Sm. ! ) A. hyalina Klltz. (Baa, p. 108, pi. 30, f. 18 ; S.B.D., i., p. 19, pi. 2, f. 28 ; Ad. Sch. Atl., pi. 26, f. 52-55*) ; plate 24, fig. 691. Frustule slightly silicious, hyaline, very broadly elliptic, with apices slightly truncate. Valve very broad, with very convex dorsum. Ventral margin and raphe straight. Valves rather strongly striated longitudinally, with striae parallel to the dorsal curvature. Transverse striae excessively fine. Length, 5 to 8 c.d.m. Brackish. — England (W. Sm, ! Norman, Stolterfoth) ; Ireland (O'Meara) ; France ; Germany ; Denmark ; Norway, etc. AMPHORA. 139 A. acuta Greg. (Diat. of Clyde, p. 52. pi. 6, f. 93 ; Ad. Sch. Atl., pi. 26, f. 19 ; 20*) ; plate 24, fig. 692. Frustule elliptic, with truncate apices. Valve broad, with dorsal margin regularly arcuate, ventral margin flat. Stauros rather broad, very distinct. Raphe straight. Stride very distinct, distinctly moniliform, 14 in i c.d.m. Length, 8-5 to 13 c.d.m. Marine. — Scotland ; Greenland ; P'inmark, etc. A. laevis Greg. (Diat. of Clyde, p. 42, pi. 4, f. 74 ; Ad. Sch. Atl., pi. 26, f. 8*) ; plate 24, fig. 693. Frustule subquadrangular or elongate, with rounded apices, median portion constricted. Valve narrow, arcuate, with apices slightly tapering- rostrate, raphe gradually inflexed, stauros narrow ; stria; fine, 24 in 1 c.d.m. Length, 3 to 4 c.d.m. Marine. — England ; Scotland ; Ireland. A. laevissima Greg. (Diat. of Clyde, p. 41, pi. 4, f. 72; H.v.H. Atl., pi. 1, f. 15*; Type No. 8); plate 24, fig. 694. Frustule linear-oblong, with rounded apices ; excessively hyaline. Valve with raphe abruptly inflexed towards the median portion, with a rather broad stauros. Stria; almost invisible. Length, 5 to 6 c.d.m. Marine. — England; Scotland; Ireland ; Norway ; Finmark ; probably indigenous to Belgium, but it has not yet been recorded. A. ostrearia Breb. ! (in Kutz. Spec. Alg. p. 94; H.v.H. Atl., pi. 1, f. 25*) plate 1, fig. 1. Frustule elliptic-oblong, with outer margins inflated at the median portion, apices regularly rounded, sometimes slightly truncate. Valve with raphe strongly inflexed, stauros very distinct, transverse stria; about n in i c.d.m., finely punctate. Connecting zone finely striate, transversely, and showing numerous pleats on the dorsal surface. Length, 6 to 8 c.d.m. Maiine. — France ; England, etc., probably Belgium, but not yet recorded. Sub-var. Belgica Grun. (In H.V.H.'s Type, No. 74). Distinguished from A. ostrearia by the outline of the frustules being more quadrate, by the ventral portion of the valves being a little narrower, and by the stria; being closer (16 to 17 in *oi mm. in the middle of the valve) and very finely punctate. Length, '033 — "048 mm. ; breadth, -o2i — '022 mm. Marine. — Blankenberghe, washing of sand on seashore. 140 CYMBELLA. ll quadrata Breb. ! (A. quadi-ata Breb. in Kiitz. Alg., p. 94 ; H.V.H. Atl., pi. 1, f. 24*), plate 1, fig. 2. Differs from the preceding by its subquadrangular form and its hyaline condition, which renders details almost invisible. Marine. — Same habitats as type-form. England (Norm.) ; Scotland (Greg.). The Amphora membranacea of W. Sm. (S.B.D., i., p. 20, pi. 2.,f. 29), according to authentic specimens from his herbarium, in our opinion, is only a narrow and oval form of A. ostrearia. The figure of W. Smith well repre- sents its type-form. England ; various localities (Sussex, W. Sm. !) Amphoropsis Grun. in Syn. (1883). Auricula Castr. (1873). These two genera should be included in the Amphiprora and are described subsequently. GENUS 2— CYMBELLA AG., 1830. Frustules free or stipitate, with valves more or less cymbiform, divided into two unequal portions by the raphe and the central nodule eccentric. Raphe generally more or less arcuate. Endochrome as in the Amphora. The C/mbella are asymmetrical Navicula, presenting all possible variations from the type form Navicula, from having a lanceolate, straight valve to a valve in the form of an arc. Authors have, from the genus Cymbella, created two different genera, the genus Cymbella, properly so called, with frustules free and the genus Cocconema, the frustules of which are stipitate. All the Cymbella of our Section II. belong to the old genus Cocconema Ehr. Cocconema having been described in 1829, and Cymbella only dating from 1830, the earlier name ought to prevail, but in order not to create confusion, we have preferred to adopt the later, v.hich is now exclusively employed. We are not aware to what Syncyc/ia Ehr. iSjj, refers, in which this author includes cymbelliform frustules arranged in a ring, and of which one species S. Salfia, had been observed at Wismar, in the Baltic Sea on some fucus. We are much inclined to believe that this observation should Fig. 26.— Cymbella . , ... : . Ehrenbergu Kiitz, be accepted with caution. CYM BELLA. I4I ANALYSIS OF SPECIES. I. Dorsal and ventral margins bent in contrary directions. Valve broadly lanceolate or sub- elliptic. Apices slightly produced . Apices strongly rostrate-cuspidate Apices rostrate-capitate C. Ehrenbergii. C cuspidata. C. amphicephala. Valve very elongated with dorsal margin much more arcuate than the ventral margin. Apices imper- ceptibly attenuate. Apices obtuse ; raphe surrounded with a hyaline zone ; stria; with well marked puncta . . . C. Apices sub-acute ; raphe without a hyaline zone ; strife with puncta faint . . . . . C. f Ventral margin strongly gibbous in the median portion ; raphe edged throughout its entire length with a broad hvaline zone .... C Apices slightly rostrate or rostrate- subcapi- tate. Ventral margin not gibbous. Raphe very marked arcuate, string distant, well obtusa. pusilla. leptoceras. amnis. f Apices valve sides rostrate - subcapitate ; with almost equal C. subsequalis. Raphe almost straight ; strife not well marked. Apices strongly rostrate-capitate Valve elongate, very narrow; dor- sal margin slight- ly arcuate ; strife very delicate, 18 to 22 in 1 c.d.m. Valve rather broad, with dorsal mar- gin very arcuate ; strife rather dis- tinct about 14 in 1 c.d.m. Striae delicate 24 to 30 in 1 c.d.m. . Strife robust about 14 in 1 c.d.m. . Apices slightly tapering, rostrate. C. delicatula. Valve naviculoid, sub- lanceolate-linear mar- gins scarcely bent, almost straight, strife delicate 1 I Strife approximate, valves with apices rostrate-capitate Strife very distiant, apices scarcely contracted laevis. microcepbala. tumidula. aequalis. abnormis. II. Ventral and dorsal margins bent in the same direction: raphe bent parallel to dorsal margin. Terminal nodules not very much elongated. Striation not interrupted by a broad hyaline space on the ventral side of the valve. Striation in- terrupted by a broad hyaline space on the ventral side of the valve. Curvature of raphe con- siderable and raphe bent regularly parallel to the dorsal margin. ( Raphe surrounded with a broad hyaline zone ; strife with coarse punctfe C. gastroides. Raphe with a narrow hyaline zone ; strife with puncta rather fine C. lanceolata. Curvature of raphe inflected on the ventral side in the middle of the valve C. cymbiformis. Valves with apices for some length pro- duced-rostrate ; central nodule usually having a small furrow across it ; cen- tral nodule often accompanied by one or two isolated granules Apices obtuse, rounded, slightly or not at all produced rostrate ; nodule sur- rounded by 2 to 5 isolated granules Terminal ncdules very much elongated , C. tumida. C. Cistula. C. Helvetica. 142 CYMBELLA. Sect. i. Ventral and dorsal margins bent in contrary directions. § Valve broadly lanceolate or sub-elliptic. C. Ehrenbergii Kutz. (Bac. p. 79, pi. 6, f. n. h.v.h. Atl., pi. 2, f. 1, 2*; Type No. 15) ; plate i, fig. 22. Valves broadly elliptic-lanceolate, apices slightly produced rostrate ; raphe a little bent, surrounded by a broad hyaline zone, rather enlarged near the central nodule ; transverse striae about 8 in 1 c.d.m., robust and very finely divided crosswise. Length 6 to 13 c.d.m. Fresh water. — Common. C. cuspidata Kiitz. (Bac p. 79. pi. 3, f. 40; H.V.H. Atl, pi. 2, f- 3* ; Type No. 16); plate 1, fig. 23. Valves broadly lanceolate, ventral margin sometimes depressed, with apices longitudinally rostrate-cuspidate ; raphe bent, surrounded by a faint hyaline zone, very inflated round the central nodule ; transverse striae 6 in i c.d.m. in the middle of the valve, 12 in i c.d.m. at apices, finely divided crosswise. Length 6 to 8 c.d.m. Fresh water.- — Common. /3. naviculiformis Auersw. (in Rab. Alg, n. 1065; H.V.H. Atl., pi. 2, f. 5*); plate 1, fig. 24. Considerably smaller, apices rostrate ; raphe straight ; hyaline zone very inflated round the central nodule; striae finely punctate, about 15 in 1 c.d.m. ; length 3 to 4 c.d.m. Fresh water. — Belgium, Ard. Liege. (De Wild.). Denmark (Heiberg). C. amphicephala Nsegeli (in Kiitz. Sp. Alg., p. 890; H.V.H. Atl., pi. 2, f. 6*; Type No. 19) ; plate 1, fig. 25. Valves elliptic with apices rostrate-capitate ; ventral margin sometimes depressed ; raphe almost straight ; hyaline zone narrow, slightly inflated round the central nodule, where the striae are also more distant; striae finely punctate, about 12 to 14 in 1 c.d.m. Length 2^25 to 3 c.d.m. Fresh water.— Antwerp, etc. (H.V.H.), Ard. Liege. (DeWild.) 13. Anglica Lag. (Diat. Spitzb., p. 42, pi. 2, f. 18*), plate 25, fig. 695- Only differs from C. amphicephala in the hyaline space surrounding the raphe. This hyaline space is more visible in the C. Anglica. Fresh water.— Belgium, Ard. Liege. (De Wild.). England (W. Sm.). Spitzbergen (Lagerstedt.) CYMBELLA. 1 43 § § Valve very elongate, with dorsal margin much more arcuate than ventral margin. C. subaequalis Grun. ! (H.v.h. Atl., pi. 3, f. 2; Suppl. f. i* ; Type No. 29); plate 1, fig. 26. Valves almost symmetrical, oblong-lanceolate, slightly attenuate, with apices obtuse, rounded, sub-capitate, ventral margin very slightly less arcuate than the dorsal margin ; raphe almost straight, surrounded by a hyaline zone rather broad, and dilated round the central nodule ; striae very radiant, finely punctate, about 10 in 1 c.d.m. in the middle of the valve, 14 near the apices. Length 4 c.d.m. Fresh water. — Botanical Gardens, Brussels (Del.) ; Ard. Liege. (De Wild.) [According to Professor Cleve, this form should really constitute the C. pequalis of W. Sm.] C. obtusa Greg. ! (q.j.m.s., 1856, p. 5, pi. 1, f. 19; h.v.h. Atl., pi. 3, f. ia*; in Type No. 257); plate 1, fig. 27. Valves lanceolate, with dorsal margin inflated, infinitesimally attenuate ; ventral margin almost straight, slightly inflated in the middle ; raphe straight, a little flexuous, surrounded by a slight hyaline zone, very slightly dilate on the dorsal side round the central nodule. Median stria 12, terminal 15 in 1 c.d.m. Length about 3 c.d.m. Fresh water. — Mot yet found in Belgium ; Scotland (Gregory) ; England (Norman.). C. pusilla Grun. ! (in Ad. Schm. Atl., pi. 9, f. 36, 37 ; H.V.H. Atl., pi. 3, f. 5* ; in Type No. 12) ; plate 1, fig. 28. Valves very lanceolate, with apices very attenuate, slightly obtuse ; dorsal margin very arcuate, ventral margin almost straight, very slightly convex in the median part ; raphe straight, surrounded by a narrow hyaline zone not dilated in the middle. Median striae 14, terminal 16 in 1 c.d.m., finely punctate, Length about 3 to 4 c.d.m. Brackish water.— Blankenberghe (H.V.H.); Ard. Liege. (De Wild). C. delicatula Kutz. (Spec. Aig., pi. 59,11. 13; h.v.h. Atl., pi. 3, f. 6* ; Type No. 31) ; plate 1, fig. 29. Valves narrowly lanceolate, divided very unequally by the raphe, with apices produced-rostrate ; dorsal margin considerably arcuate, ventral margin 144 CYMBELLA. straight, slightly arcuate, not gibbous ; raphe almost straight, slightly flexuous, surrounded by a very narrow hyaline zone, in no parts inflated ; stria? delicate, slightly radiant, visible with difficulty; dorsal 18, ventral 22 in 1 c.d.m. Length about 3 to 4 c.d.m. Freshwater. — Frahan, Belgium (Delogne); Aid. Lidge. (DeWild. ) C. laevis Naegeli ! (h.v.h. Atl., pi. 3, f. 7*; in Type No. 257); plate 1, fig. 30. Valves lanceolate, with dorsal margin very arcuate, ventral margin very slightly convex. Apices very shortly rostrate, rostrum narrow. Raphe very slightly arcuate, surrounded by a narrow hyaline zone ; striae faintly marked, 14 in 1 c.d.m. Length about 3 c.d.m. Fresh water. — Ard. Li£ge. (De Wild.) ; S. Abbe Head, England. Var. rupicola Grun. — (C. ruphola Gr. in A. Schm. Atl., pi. 71, f. 70-71*; in H.V.H. Type No. 28) ; plate 25, fig. 696. Differs only from the type form by its valves being somewhat more symmetrical. Fresh water. — Scotland. C. affinis Kiitz. (Bac, p. 80, pi. 6, f. 14 ; H.V.H. Atl., pi. 2, f. 19* ; Type No. 26); plate 1, fig 31. Short, ventricose ; valves broadly lanceolate, with dorsal margin very convex, ventral margin very slightly convex, not gibbous ; apices produced rostrate ; raphe very arcuate, parallel to dorsal side, surrounded by a narrow hyaline zone; stride median, dorsal 9, ventral n in 1 c.d.m. Length 2*5 c.d.m. Fresh water. — Antwerp, Brussels, Louvain (H.V.H.) ; England (W. Sm., Norman); Scotland (Greg.) ; Ireland (W. Sm., O'Me.) C. leptoceras Kiitz. (Bac, p. 79, pi. 6, f. 14; h.v.h. Atl., pi. 3, f. 24* ; in Type No. 211) plate 1, fig. 32. Valves rather broadly lanceolate, short, with apices attenuate, sub-obtuse ; dorsum very arcuate, ventral margin extremely gibbous ; raphe almost straight, slightly flexuous, surrounded throughout its length by a rather broad hyaline zone; striae well marked, about 8 in 1 c.d.m. Mean length, 2 to 3 c.d.m. Fresh water. — Brussels, Antwerp, &c. Var (3 elongata (C. leptoceras H.V.H. Atl., pi. 3, f. 18 ; suppl., f. 2* ; in Type No. 211) plate 1, fig. 33. CYM BELLA. M5 Considerably longer than the preceding, with apices much more rostrate, ventral margin almost straight and strongly gibbous. Length 3.5 to 4 c.d.m. Freshwater. Louvain, Brussels, Antwerp, etc. C. microcephala Grun. (h.v.h. Atl. pi. 8, f. 36—39*- in Type No. 211), plate 1, fig. 34, 34. Valves rather narrowly lanceolate, scarcely cymbiform, with apices strongly rostrate-capitate; raphe sub-arcuate; stria? delicate, 24 in large forms, 28 to 30 in small forms. Length 1.5 to 2.3 c.d.m. Fresh water. Brussels (Delogne). C. tumidula Grun. (in Ad. Schm. Atl., pi. 9, f. 33* ; h.v.h. Type No. 27 sub 110m. C. affinis var. tumidula); plate 25, fig. 697. Valve linear-lanceolate, with rostrate apices. Dorsal margin very arcuate ; ventral margin straight or slightly gibbous at the median portion. Raphe somewhat eccentric; surrounded by a narrow hyaline area. Striae about 14 in 1 c.d.m., somewhat radiant, punctate, shortened on the dorsal side round the central nodule, where they leave a small rounded hyaline area, while on the ventral side each of the two median striae are terminated by a distant isolated dot. Length y$ to 3*5 c.d.m. Breadth 0*75 to 10 c.d.m. Fresh water. — England (Thames, Oxford (F. Okeden) ). This form is very closely allied to C. affinis, and it has been recorded with it by \V. Arnott and Grunow. The dorsal, median, hyaline area does not exist in C. affinis ; in that form there is seen on the ventral side one coarse isolated dot, but never two, the striae also are in an equal manner more robust and more distant. § § § Naviculoid, sub-lanceolate-linear valve, both margins scarcely bent, almost straight, striae delicate. C. aequalis W. Sm. (S.B.D. ii., p. 84; Ad. Schm. Atl, pi. 9, f. 69*) plate 25, fig. 698. Valve lanceolate almost naviculoid, with dorsal margin regularly arcuate, slightly produced at apex. Ventral margin rather more strongly arcuate, with apices rostrate-capitate. Raphe and central nodule surrounded by a well marked hyaline space. Striae delicate, about 12-13 in 1 c.d.m. Length, 3"5 to 6 cd.m. Fresh water. — England, various localities ; Germany, etc. ? According to Prof. Cleve, this form should be the C. angustata of W. Sm. L 146 CYM BELLA. C. abnormis Grun. (in H.V.H. Syn., pi. 3, f. 8*; Bot. Centbl, 1880, p. 249), plate 25, fig. 699- Valve sub symmetrical with apices slightly produced, dorsal margin arcuate, ventral margin almost straight, slightly inflated at the median portion. Raphe straight, surrounded by a rather broad hyaline space. Striae rather strong, not moniliform, very distant, about 10 in i c.d.m. : absent in median portion where they leave a broad stauroform blank space. Length, about 2-5 c.d.m. Breadth, o-5 c.d.m. Fresh water — France (Normandy), Sweden, Norway (Grunow) Sec. II. — Ventral and dorsal margins bent in the same direction ; raphe with concavity turned towards the ventral margin. % Terminal nodules not very elongate. [a.) STRIATION NOT INTERRUPTED BY A BROAD HYALINE SPACE ON THE VENTRAL SIDE OF THE VALVE. C. gastroides KutZ. (Baa, p. 79, pi. 6, f. 4 b ; H.V.H. Atl., pi. 2, f. 8* ; Type 20) plate 1, fig. 35. Valve broadly cymbiform with apices obtuse, rounded ; dorsal margin arcuate, with median portion scarcely more inflated ; ventral margin very slightly concave, with median portion somewhat prominent ; raphe slightly arcuate, surrounded by a very broad hyaline zone, very slightly dilated round the central nodule ; central nodule elongate ; terminal nodules very robust ; striae very robust, 8 in 1 c.d.m., consisting of coarse distant beads. Length, about 15 c.d.m. Fresh water. — Rather common. /3. minor. (H.V.H. Atl., pi. 2, f. 9*) plate 1, fig. 36. Short, very broad, with raphe strongly arcuate. Length, 7 to 8 c.d.m. Fresh water.— Not so common as the type form. C. lanceolata Ehr. (Coxonewa lanceolatum Ehr. Inf. p. 224, pi. 19, f. 6; H.V.H. Atl., pi. 2, f. 7*; Type No. 18), plate 1, fig. 37. Valve cymbiform with dorsal margin strongly convex, ventral margin concave, inflated at the median portion ; apices obtuse, raphe very arcuate, surrounded by a very narrow hyaline zone, scarcely dilated near the central nodule ; central nodule rather large, elongate ; terminal nodules of medium CYM BELLA. M7 size. Stride about 7 to 8 in 1 c.d.m. distinctly moniliform with granules small, approximate. Frustules stipitate in living state. Length, 8 to 15 c.d.m. Fresh water. — Very common. C. Cymbiformis Ehr. (Cocconema cymbiforme Ehr. Abh., 1835. Inf. p. 225, pi. 19; H.V.H. Atl., pi. 2, f. 11, a.b.c.*; Type No. 22), plate 1, fig- 38. Valve with dorsal margin slightly arcuate, ventral margin slightly concave, a little inflated in the middle ; apices obtuse-rounded, sometimes somewhat produced. Raphe surrounded by a narrow hyaline zone, slightly inflated near the central nodule, and showing there an isolated punctum, unilateral (omitted in the figure) ; raphe slightly arcuate, with its convexity turned towards the dorsal margin as far as the central nodule, where it is abruptly inflected towards the ventral margin ; striae about 8 in 1 c.d.m., coarse, very finely divided cross-wise. Frustules stipitate. Length, 5 to 10 c.d.m. Fresh water. — Not so common? Belgium, England, France, Norway, etc. /j. parva. (Cocconema parvum, W. Sm.) (H.V.H. Atl., pi. 2, f. 14*, Type No. 23), plate 1, fig. 39. Smaller and often more inflated, with apices generally slightly produced- rostrate ; striae as in the type form, but not so distant near the central nodule. Length 3 to 5 c.d.m. Freshwater. — Rather common ? Belgium, England, Ireland. (b.) STRIATION INTERRUPTED BY A BROAD HYALINE SPACE ON THE VENTRAL SIDE OF THE VALVE. C. Cistula Hempr. (Cocconema Cislula Ehr. Inf., p. 224, pi. 19, f. 7 ; H.V.H. Atl., pi. 2, f. 12-13*, Type No. 24— var. curta ; Type No. 25), plate 1, fig. 40. Valve with dorsal margin very arcuate, median portion strongly gibbous, ventral margin slightly concave, inflated in the middle ; apices obtuse- rounded ; raphe regularly bent, surrounded with a rather broad hyaline zone and strongly inflated near the central nodule on the ventral side ; the diiated portion showing from 2 to 5 isolated granules; striae 7 to 8 in 1 c.d.m.; very robust, finely divided cross-wise. Length, 5 to 9 c.d.m. Frustule stipitate. Fresh water.— Rather common, England, West Ireland. Prance, Belgium, Holstein, etc. /?. maculata. (C. maculata Kiilz. nee Breb. ; H.V.H. Atl., pi. 2, f. 16, 17*), plate i, fig 4t. Ventricose, with the isolated granules generally absent. Fresh water. — Rather common, like the type form. 148 ENCYONEMA. C. tumida Breb (Cocconema tumidum Brcb. ! in Kutz Sp. Alg., p. 6c, 11. 5 ; H.V.H., pi. 2, f. 10*; Type No. 21), plate 1, fig. 42. Valves ventricose, with dorsal margin very arcuate, ventral margin concave, inflated in the middle, apices very produced-rostrate, truncate or rounded. Raphe very arcuate, surrounded by a rather broad hyaline zone, very considerably inflated round the central nodule, dilated portion some- times showing one or two isolated granules ; central nodule generally having a small furrow across it in the middle ; stria; robust, quite moniliform, 8 to 9 in 1 c.d.m. Length, about 6 c.d.m. Frustule stipitate. Fresh or slightly brackish water. — Antwerp, Louvain, Ostend, etc. § § Terminal nodules very elongate C. Helvetica Kutz. ! (Baa, p. 79, pi. 6, f. 13; h.v.h. Atl., pi. 2, f. 15*; Type No. 32); plate 1, fig. 43. Valve very lanceolate, with dorsal margin rather convex, ventral margin very slightly concave, almost straight, abruptly inflated in just the middle portion ; raphe slightly bent, with curvature inflected at the middle of the valve towards the ventral margin \ raphe surrounded by a narrow hyaline zone, slightly inflated near the central nodule ; terminal nodules very long, in the form of a coarse inverted comma ; stria; rather well marked, divided cross- wise, about 8 to 9 in 1 c.d.m. Mean length about 7 c.d.m. Fresh water. — Very common, and found in all the countries comprised within our radius. GENUS 3.— ENCYONEMA KUTZ., 1833. Fig. 27. — Encyonema prostration (Berk.) Ralfs, ENCYONEMA. 1 49 Frustules generally enclosed in tubes. Valve more or less cymbi- form, divided unequally into two parts by the raphe and the central nodule, which is eccentric. Raphe straight. Terminal nodules con- siderably distant from the apices. Endochrome as in the Amphora. ANALYSIS OF SPECIES. Raphe surrounded by f Apices broadly obtuse, rounded. . E. prostratum. a hyaline zone inflated j round the central no- \ dule. V Apices acute . . . E. turgidum. f Ventral portion of valve rather broad ; ventral margin rather strongly inflated, Hyaline zone not in- J specially in the median part . E. caspitosum. fkled round the cen- j ■.- , , tral nodule entral portion very narrow ; ventral margin straight or concave, rarely a little I gibbous . E. ventricosum. Length of valve never exceeding 3 to 4 times its breadth. Valves very f Striae very conspicuous, distant, having the same length throughout, elongated, ventral margin concave . . . . . . E. lunatum. length 5-9 -J times its Striae fine, approximate, shorter near the central nodule ; ventral breadth. l_ margin straight, or inflated in the middle . . . . E, gracile. Sect. I. — Length of valve never exceeding three to four times its breadth. § Raphe surrounded by a hyaline zone, inflated round the central nodule. E. prostratum Ralfs ! (Ann. & Mag., vol. i6,pl. 3, f. 3; H.V.H. Atl. pi. 3, f. 9, 10, 11*; Type No. 34); plate 1, fig. 44. Valve large, with dorsal side considerably inflated, ventral side with slight curvature ; apices abruptly produced, obtuse, straight, recurved on ventral side ; raphe straight, with its median ends slightly arcuate towards the dorsal margin, surrounded by a hyaline zone, broad and strongly inflated round the central nodule ; terminal nodules very large and extremely elongate towards the dorsal margin, completely surrounded by stria?, except where they touch the raphe; striae 6 or 7 in 1 c.d.m., robust (simulating costae), divided cross- wise ; some near the central nodule being often only half as long as others. Length 6 to 9 c.d.m. Fresh water. — Almost everywhere. E. turgidum (Greg.) Grun. ! (Cymbella turgida Greg. Q.J. M.S. 1856, p. 5, pi. 1, f. 18; H.V.H, Atl. pi. 3, f. 12*), plate 1, fig. 45. Valve cymbiform with dorsum very convex, venter almost straight, some- what inflated in the middle ; apices sub-acute ; raphe straight, surrounded by 150 ENCYONEMA. ;i rather broad hyaline /.one, inflated round the central nodule, and extending as far as the apex of the valve; stria- 7 or 8 in 1 cd.m, ; faint, finely divided < ross wise, no! intermixed near the central nodule with shorter stria-. Length, 5 to 6 in 1 cd.m. Fresh water, Not yet found in Belgium, Scotland (Gregory), West Ireland (West) ; Hyaline zone not dilated round the central nodule. E. csespitosum Kutz. (Spec. Alg., p. 61 \ 11. v. II. Ail. Supp., f. 3* ; Type No. 25), plate 1, fig. 46. Valve very broadly cymbi orm, with apices straight, obtuse, scarcely constricted ; dorsal margin broadly convex, ventral margin regularly inflated ; raphe almost straight, surrounded by a narrow hyaline /one, slightly inflated in the middle; striae robust, divided crosswise, 10 to 12 in T cd.m. Length, about 3 C.d.m. Fresh water. Here and there in sm.ill quantities, almost everywhere very variable, passes into the t' illowing forms by all intermediate stages. Var. Auerswaldii. (E. Auenwaldi Rabh. I I.Y.I I. Atl., pi. 3, f. 14*), plate 1, fig. 47- Apices rounded, produced subrostrate. Var. lata. (II.Y II. Atl., pi. 3, I. 13*), plate 1, fig. 48. Valve very widely lanceolate, sub elliptic ; apices very obtuse. E. ventricosum Kutz. (Bac, p. 80; H.V.H. Atl., pi. 3, f. 17*; Types Nos. 36, 37, 38), plate i, fig. 49. Valve cymbiform, somewhat elongated, apices often rather abruptly attenuate; dorsal margin rounded, ventral margin straight, or almost straight ; raphe straight, surrounded by a narrow hyaline zone, not inflated round the central nodule ; stri;u faint, about 12 to 16 in 1 c.d.m. at the middle of the valve, according to the size of the latter. Length, very variable, from 1-25 to 2*5 c.d.m. Fresh w ater.- Rather common. This species is excessively variable, not only in size, but also as to form ; the apices are sometimes obtuse, in no way constricted, at other times rather constricted longitudinally, at other times somewhat prolonged into points beyond the ventral margin. Cleve unites this form with E. acspitosum. Sec. II. — Valves very elongated, being 5-9 times longer than broad. E. lunatum (W. Sm.) H.V.H. (Cymbella lunata IV. SmJ in Grev. Ann., 2nd ser., vol. 15, pi. 0, f. 5, H.V.H. Syn., pi. 3, f. 23*, Type K°- 39)> plate 28, fig. 791 bis. c. ENCYONEMA. '5' Valve cymbiform, with dorsum arcuate, ventral margin slightly concave with apices sub obtuse. Striae very well marked, distant, to in i c.d.m., leaving off everywhere at a short distance from raphe. Length, about 3 c.d.m. Breadth, 1*5 c.d.m. in the middle portion. Fresli water. — England, Scotland, Braerrrai (Di Balfour) W. Sm. ! E. gracile Rabh. (Sussw. Diat, p. 25, pL io,Suppl. f. 1 ; ii.v.h. Atl., pi. 3, f. 20,*) plate 28, fig. 791, bis. b. Dorsal margin arcuate; ventral margin inflated al the median portion. Striae delicate, about 12 to r} in 1 c.d.m., leaving an elongated hyaline area round the central nodule. Length about 6 to 8 c.d.m. ; breadth, about 1 c.d.m. Freshwater. Germany (Rabenhorst) ; Wesl Ireland (West). Var. Scotica (CymM/a Scotica. W. Sm. S.B.D. i., p. 18, pi. 2, f. 25 ; ii. p. 84. II.V.H. Atl., pi. 3, f. 21* j in Type No. 2741, plate 28, fig. 791, bis. a. Ventrai margin straight, not inflated at the median portion ; median striae on dorsal side appearing to coal ( ce in the central nodule. Striation and size as in type form. Fresh water. Ard, Lfe| i l" Wild), England, Scotland, vai bo o w a S a a o o if u § * o >-. 3 09 O o o 3 o ■r-4 u in O ft -a o o 2 a § I SI o ro O ft tig ■3 . o i-H -r-t o u a 0) ft o .1-1 I— I o o W h •f-i 7? d o ft rt 3 I— ( ft o a p. a o o ft o o o rt >> •— < <1) >-t M 3 w u C o o _rt o s rt a _o K O i- a) o u c I § *> — u 4) 0 rt o-g 8.2 « > CJ >. 0) 1) ■ 1- ~ rt rt 0 O . 0) 3 ^ .2 tM .rt B-l h 0 rt en \£ J3 rt 'C tn If! 3 ^ A u T3 .5 O rt £ B O Ul .CD " ■- i~ i2 b, u 3 in S Q o w u o _, M o c rt s: rt b/D 3 o o S rt a 'bi) rt E;d o o S2 E rt bo 3 o p < 3 O 3 o 'ft in c O bfi u. O w ■_ A o tj aj'd'rtS^rt'^aj'J >crt^ ^ ft ° 32 m 1/1 *•* HI a 9 ■ — *j o •- 0.1: r* c rt > 2 - 4 « .J. •- >^ — I) ^ 3 _oj •; o r^ tn O -rt v- O O O 3 rt 3 rt !* 3 E 3 S Ui. o c E 52 75 rt £ J3 "2 S « S rt ~ 3 3 "3 3 O u X; *-; u O "> o O rt •a in o 3 O 3 V o S3 73 rt uj O ■- "3 8 5 '£ " > g^= £ 3 rt 5? k> y 3 C rt o o uuinSuiupBrib }ou sa.\ii\\ rt > -O T5 rt 1) O O ft 3 o OJ ft 3 tn * O 5 tf ••-» • ^.^ 0 t/1 a> 4 - r- 3 > a HJ o rt o 3 fc MASTOGLOIA. GENUS 4.— MASTOGLOIA. THWAITES, 1848. T53 Frustules naviculoid, most frequently enclosed in a gelatinous envelope, with valves furnished with loculi or marginal cells formed of silicious plates interposed between the connecting membrane and the valve, to which they most frequently appear to be adherent. Fig. 28. — ( 1 2 J .1/. lanceolata Tht. ; fjj .1/. Smifhii T/iw., var. lacustris Grun. ANALYSIS OF SPECIES. Valves with striae not inter- rupted by sulci, making to- gether the figure of a lyre. Valve lanceolate, with loculi arranged in an arcuate row. Valve linear- elliptic with loculi arranged in a straight row. More than five loculi with out- line not rounded. Strias radiant up to the apices of the valve. Loculi rather broad, occupying almost half of the margin of the valve Loculi narrow, very numerous, occupy- ing almost the entire outline of the valve . Strire almost parallel at the mid- dle of the valve, convergent at apices 3 to 5 loculi, with rounded outline . ( Strias rr- gent radiant, diver- -! Striae radiant, con- vergent Apices abruptly attenuate ; striae finely punctate ; marine or brackish Apices cuneate ; striae with coarse puncta ; fresh water .... M. Smithii. M. apiculata. M. lanceolata. M. exigua. M. Closeii. M. Dansei. M. Grevillei. Valves with striae interrupted by sulci, making together the figure of a lyre M. Braunii. i54 MASTOGLOIA. A. — Valves with strice not interrupted by sulci or hyaline spaces making together the figure of a lyre. 1. Valve lanceolate with loculi arranged in an arcuate row. M. Smithii Thwaites. (W.Sm., S.B.D., ii., p. 65, pi. 54, f. 341, H.V.H. AtL, pi. 4, f. 13* ; Type No. 46), plate 2, fig. 60. Valves elliptical with apices often slightly produced, rostrate ; marginal plates broad ; attenuate at the apices ; showing from 6 to 8 loculi, central nodule slightly extended laterally ; striae robust, distinctly punctate, radiant up to the extremity of the valves, 15 to 17 in 1 c.d.m. Length, 3 to 4-5 c. d. m . Fresh and brackish water.— Bergh, Brabant (Delogne), Antwerp (P.G.), Blankenberghe (H.V.H.).— England (W. Sm. ! Kitton), Ireland (O'Meara, West). Var. lacustris Grun. (H.V.H. AtL, pi. 4, f. 14* ; Type No. 47), plate 2, fig. 61. Differs from the type form by being narrower and by the nodule being much more extended laterally. Mixed with the type form at Bergh. M. apiculata W. Sm. ! (s.b.d. ii., p. 65, pi. 62, f. 387*), plate 25, fig. 700. Valves oval or lanceolate-elliptical, with apices apiculate, obtuse. Loculi narrow, very numerous, varying from 30 to 50, and arranged in a regular arc, which occupies nearly the entire outline of the valve ; stria; transverse, distinctly punctate, radiant, up to apices of the valves, about 15 in 1 c.d.m. Length of valve 4 to 7 c.d.m. ; breadth, 1*5 to 2 c.d.m. Brackish water. — Shores of England (W. Sm. !), Ireland (O'Meara), Norway, France, etc. Will probably also be found in Belgium. M. lanceolata Thwaites. (w. Sm., s.b.d. i., pi. 54, f. 340 ; N. Meleagris Kittz. H.V.H. Atl., pi. 4, f. 15, 16, 17*), plate 2, fig. 62. Valves lanceolate, infinitesimally attenuate up to the sub-obtuse apices ; loculi generally numerous ; nodule not extended laterally ; stria; about 20 in 1 c.d.m., slightly radiant nearly up the apices, where they become convergent. Length, about 5 c.d.m. Brackish water. — Not yet found in Belgium. England, Ireland, Holland, Denmark, Sweden. MASTOGLOIA. 1 55 M. exigua Lewis. (Notes on new and rare spec, 1861, pi. 2, f. 5 ; H.V.H. Atl., pi. 4, f. 25, 26* ; Type No. 50), plate 2, fig. 63. Valves lanceolate, sometimes slightly produced, sub rostrate ; loculi very few (often only 3), with rounded outline ; strios slightly radiate, 20 in 1 c.d.m. Length, 25 to 3-5 c.d.m. Brackish water. — Rare? Blankenberghe, Antwerp (Scheldt, dry dock), H.V.H. England (H.V.H., Type 50). M. Closeii O'Meara. (Irish Diat., p. 326, pi. 29, f. 10*) plate 25, fig. 701. Valve elliptical, sub-rhomboid, with apices slightly acute ; raphe straight, with very narrow hyaline area. Loculi, 5 ; the three central ones rounded, large ; the two terminal elongated, abruptly attenuate. Striae rather fine, very radiate, convergent, reaching the raphe. Length of valve, 4^5 c.d.m. ; breadth, 2 c.d.m. Marine and brackish water. — Ireland (O'Meara). 2. Valve linear-elliptic, with loculi arranged in a straight row. M. Dansei Thwaites. ! (w. Sm., s.B.D. i., pi. 62, f. 388; H.V.H. Atl., pi. 4, f. 18*; in Types Nos. 46 and 47 — Var. elliptica in Types No. 103 and 106), plate 2, fig. 64. Valve linear, elliptical, with apices slightly produced, broadly rounded ; loculi 8 to 20, in a straight line ; central nodule surrounded by a considerable hyaline area; stria? bent, radiate, finely punctate, 15 in 1 c.d.m. ; the central ones rather more distant. Length, 3 to 5 c.d.m. Fresh and brackish water— Blankenberghe (H.V.H.), Heyst (Debv), Bergh (Del.), Aid. Liege. (DeWild.), England (Kitton), Ireland. Var. elliptica. (M. [Frustulia] elliptica, C. Ag.), differs from the type form by the inflated elliptical form of the valve. M. Grevillei W. Sm. (w. Sm., s.B.D. i., p. 65, pi. 62, f. 389, H.V.H. Atl., pi. 4, f. 20*, Type No. 48), plate 2, fig. 65. Valve linear with apices cuneate, obtuse; loculi 15 to 20; central nodule surrounded by a hyaline area; stria? about 10 in 1 c.d.m. radiate, robust and with strong puncta, the central more distant. Length 3-5 to 5 c.d.m. Fresh water.— Ard. Liege. (De Wild). England (W, Sm, !), Ireland, Denmark, Sweden, &c. '& STIGMOPHORA. B. — Valve having hyaline spaces (sulci) together making the figure of a lyre. M. Braunii Grun. ! (Verh. Wien. 1863, pi. 13, f. 2 ; H.V.II. Atl., pi. 4, f. 21, 22* Type No. 49), plate 2, fig. 66. Valves lanceolate, with apices obtuse, slightly produced ; loculi numerous, those in the centre considerably larger than the others ; central nodule prolonged laterally ; striae about 18 in 1 c.d.m., finely punctate, interrupted on each side of the raphe by a long hyaline line united to the central nodule. Length, 5 c.d.m. Brackish water. — Heyst (Deby), — England (Kitton), — North Sea, Var. pumila Grun.! (H.V.H. Atl., pi. 4, f. 23). Small, slender, with hyaline spaces in a double curve ; striae 23 to 24 in 1 c.d.m. Length, about 3 c.d.m. Not yet found in Belgium. Some authors include the Ortlioneis in the genus Mastogloia in con- sequence of their marginal loculi ; we have preferred to retain them in the Cocconeideae, to which they appear to have greater affinity, on account of their structure as a whole. GENUS 4*.— STIGMOPHORA WALLICH, i860. The genus Stigmophora was created by Wallich for two species of Mastogloia from Bengal. These two species differ from Mas'ogloia in the first place in the number of the loculi which are only two, and next in each of the loculi, according to Wallich, having a central dot, but this we have been unable to discover in the example of St. rostrata in our possession. The two species of stigmo- phora are St. lanceolata Wall. (represented in the text) and St. rostrata Wall, which is distin- guished by its apices being ex- tremely rostrate, produced, and bearing 7 to 8 coarse dots on the raphe. The genus Stigmophora should Fig. 28. — Stigmophora lanceolata, after Wallich. DICTYONEIS. 157 Sifl ■': 1 I gag 2;f: I be re-united with Mastogloia or made a special section of it, which would have for its characteristic the binary number of the loculi and their isolation at the median part of the valve where they are found. In true Mastogloia the loculi always form a long marginal line, either straight or curved. GENUS 5.— DICTYONEIS CLEVE, 1890. Valve elongated, of variable form, contracted or not at the median part. Raphe straight, surrounded by a very narrow hyaline zone, with apices generally in opposite directions. Valve with two layers superposed ; the external with fine puncta arranged in quinqunx, the interior with cells broader, vesiculate, giving a reticulate appearance to the stratum. Marginal cells often much broader than the others and simulating loculi. The genus Dictyoneis includes eight species which had been ranked by others in the genera Navicida, Pseudo-diploneis and Mastogloia. None ot these species belong to the North Sea. The form represented opposite belongs to D. marginata CI. The forms united under the genus Dictyoneis have a different structure to all other raphidiese ; this structure being in reality Dictyoneis marginataCl. similar to that observed in many Coscinodiscus and Triceratium. " The large marginal cells have the appearance of the loculi of the genus Mastogloia which have caused many of the species to be placed in the latter genus. However 1 find that these cells or loculi belong to the valve itself and not to a separate stratum as in the Mastogloia " (Cleve). Fig 29. 158 STAURONEIS. U-'Ji GENUS 6.— STAURONEIS EHR, 1843. Frustules free or united in a small number, differing from Navicula by the central nodule being transversely dilated into a stauros. Endochrome similar to that of the Navicula. We include in the genus Stauroneis the following groups which have been raised to genus rank by various authors : Fig. 30. — Stauroneis Phcenicenteron Ehr. Frustules not con tained in mucous tubes f Frust ' j solitary. ' Valv ( Valves with decussating striae. Staurogramma Rat). 1853. Staurosigma Grun. 1860. Pleurostauron Ra??. 1859. Endostauron Grun. 1868. ( Valves with sigmoid raphe uiDes . . I ^ Valves cohering in filaments. I. Frustules contained in mucous tubes (Schizonema W. Sm. ) ANALYSIS OF SPECIES. '5 Valves with margins not un- dulate. Valves not per- ceptibly attenuate rostrate. bifurcate Stauros very broad. f Valve not ter- /Valve broad minated by a) and large . S. Phcenicenteron. Ll™fn_Lraphe j Valve small • ^ and narrow S. gracilis. f Lumen very large, J raphe bifurcate. Frustules united together many at a time . . S. acuta Valve ter- minated by a lumen. I Lumen small, j raphe si mple. ^ Frustules isolated S. Gregorii. Stauros narrow. ( Valve very long, very narrowly ■i lanceolate . . . S. spicula. ^ Valve short, broadly lanceolate S. salina. ^ Valves with apices attenuate-rostrate . . . S. anceps. Valves short and broad ; terminal lumen very large . S. Smithii. Valves long and narrow ; terminal lumen very small . S. Legumen. , Raphe oblique, sub-sigmoid . . . . . . S. obliqua. Valves with margins - triundu late. L STAURONEIS. 1 59 /. Raphe straight. A. — Valves with margins not undulate. a.— VALVES WITH APICES NOT PERCEPTIBLY ATTENUATE ROSTRATE. * Stauros very broad, raphe bifurcated. S. Phcenicenteron Ehr. (Verb, 1843, pi. 11. 5, f. 1., h.v.h. Atl, pi. 4, f. 2*, Type No. 40) ; plate 1, fig. 50. Valve lanceolate infinitesimally attenuate up to the apices, which are obtuse, rounded, often slightly constricted ; raphe formed of a double line on the greater part of its length, and surrounded by a broad hyaline zone ; stauros, reaching the margins of the valve, very broad, generally a little dilated n jar its extremities ; striae radiant, about 14 in 1 c.d.m., finer but distinctly monililorm. Length, 10 to 17 c.d.m. Fresh water. — Rather csmnion everywheie. According to Prof. H. L. Smith S. Phcenicenteron is simply a sporangial form of »S. gracilis. S. gracilis Ehr. (Amer., pi. i, 2, f. 14, W. Sm. ! S.B.U. i., p. 59, pi. 19, 1. 186*; Type No. 41), plate 25, fig. 702. Distinguished from the preceding species by its small, narrow valve, its fine striae, 18 — 20 in 1 c d.m. Length 5.5 to 8.5 c.d.m. PVesh water. — Belgium, England. Observ. — Most authors distinguish S. gracilis Elu . from S. gracilis IV. Sm. the latter being characterised by a stauros which does not reach the margins ot the valve. But this character is illusory — appearing so in frustules set dry or imperfectly, but in good preparations which we have made with various material from the herbarium of W. Smith, as well as in preparations made by Prof. Smiih himself, this character no longer exists. We have, therefore, referred the form of W. Smith to S. gracilis Ehr., as W. Smith did himself in his Syn. Br. Diat, vol. I., p. 59, and as does also Ralfs in Pritchard, p. 913. S. acuta W. Sm. (s.b.d. i., p. 59, pi. 19, f. 187; h.v.h. Atl., pi- 4, f- 3*; Type No. 42), plate 1, fig. 51. Valves lanceolate, with margins forming a slight cavity from the median portion up to the apices, which are obtuse, and show a very distinct lumen (formed by a thickening of the internal terminal margin) ; raphe formed by a double line throughout the greater portion of its length, surrounded by a very broad hyaline zone ; stauros very broad, dilated near the margins of the valve; striae slightly radiant, about 12 in 1 c.d.m., formed of rather distant puncta. Frustules united in bands of 3 to 6 individuals with girdle view 160 STAUR0NE1S. tabular, showing the thickening of the internal apices of the valves and the connecting zone plicate-punctuate. Length, 8 to 15 c.d.m. Fresh water. — Everywhere, but not so frequent as St. Phcenicenteron. S. Gregorii Ralfs. (in Pritch., p. 913. S. amphioxys Greg, T.M.S., 1856, p. 4S, pi. 5, f. 23 ; H.V.H. Atl., Suppl. f. 4* ; in Types No. 74 and 389) ; plate 1, fig. 52. Valve lanceolate, with apices subrostrate ; more or less obtuse and show- ing a rather small lumen ; raphe simple ; stauros very broad ; striae finely granular, slightly radiant, delicate, about 18 to 20 in 1 c.d.m. Length, about 8 c.d.m. Brackish water — Biankenberghe (rare?). England (Kitton). Scotland (Greg.). ** Stauros very narrow, raphe simple. S. Spicula W. J. Hickie. (Monthly Micro. Journ., 1874, xii., p. 290; H.V.H. Atl. pi. 4, f. 9* : in Type No. 9), plate 1, fig. 53. Valve very narrowly lanceolate, infinitesimally attenuate as far as the subacute apices ; stauros very narrow, not dilated at the extremities ; raphe simple, surrounded by a narrow hyaline zone ; striae delicate, scarcely radiant, 28 in 1 c.d.m. Length, 5 to 8 c.d.m.. Brackish water. — Very rare? Antwerp, Biankenberghe. England, Swansea Dock (Okeden in H.V H., Type No. 9), Norfolk (Kitton). S. salina W. Sm. (s.B.u. i., p. 60, pi. 19, f. 188; h.v.h. Atl., pi. 10, f. 16*; Type No. 44), plate 1, fig. 54. Valve rather broadly lanceolate, with apices sometimes slightly produced- rostrate ; stauros narrow, only slightly or not enlarged at extremities ; stria? delicate, finely punctate, scarcely radiant, about 18 in t c.d.m. Length, about 5 to 6 c.d.m. ; breadth, 0.5 c.d.m. Marine. — Biankenberghe, Antwerp, England, Ireland, Denmark. b. VALVES WITH APICES ROSTRATE OR ROSTRATE-CAPITATE. S. ancepS Ehr. (Verb., p. 134, pi. ii., 1, 18; H.V.H., Atl. pi. 4, f. 4, 5*; Type No. 43), plate 1, fig. 55. Valve elliptical or elliptical-lanceolate, with apices rostrate-capitate ; stauros broad, dilated near its extremities ; raphe simple, surrounded by a broad hyaline zone; striae delicate, strongly radiant, about 20 in 1 c.d.m.; length, 3.5 to 5 c.d.m. Fresh water. — Everywhere (but not very abundant?). Var. linearis. (S. linearis KUtz. H.V.H. Atl., pi. 14, f. 8*); plate i, fig. 56. Valve with parallel margins ; apices abruptly attenuate-rostrate. ) STAURONEIS. l6l Var amphicephala (S. amphicephala Kutz. ; H.V.H. Atl. pi. 4., fig. 6 and 7* ; in Type 67) ; plate 1, fig. 57 Valve with parallel margins, apices abruptly attenuate-rostrate-capitate. These two varieties are found mixed with the type form, from which it changes completely. B. — Valves with tri-undulate margins. S. Smithii Grun. (Ueber neue etc., i860, p. 564; S. linearis, W. Sm., S.B.D. i., p. 60, pi. 19, f. 193 ; H.V.H. Atl., pi. 4, f. 10* ; Type No. 45); plate 1, fig. 58. Valve oblong lanceolate-triundulate, with apices apiculate, sub-acute, showing a lumen ; stauros rather narrow, slightly dilated at its extremities ; raphe surrounded by a narrow hyaline zone ; striae delicate, about 30 in 1 c.d.m. ; frustules united in bands by several individuals together. Length, 2 to 3 c.d.m. Fresh water — Here and there, always in small quantities. Belgium, England, Scotland, France. S. Legumen Ehr. (Mikr., pi. xxxix., 3, f. 104 ; h.v.h. Atl., pi. 4, f. 11*), plate 1, fig. 59. Valve linear with three equal undulations, apices rostrate, a little capitate, showing a lumen ; stauros rather broad, not dilated at the extremities ; raphe surrounded by a narrow hyaline zone; striae very delicate, about 28 in 1 c.d.m. Frustules in bands of several individuals together. Length about 3 c.d.m. Freshwater — Antwerp (rare). England (Kitton), Scotland (Greg.). This is probably only a narrow elongated form of the preceding. 77. — Raphe oblique, sub -sigmoid. S. obliqua Greg. ! (q.j.m.s., 1866, p. 10, pi. 1, f. 35*), plate 25, fig. 703. Valves sub-rhomboid oblong or rhombojdal lanceolate, with apices sub- acute or sub-obtuse ; raphe oblique, sub-sigmoid ; stauros enlarged infinitesi- mally up to the margins of the valve ; striae transverse, 20 to 22 in 1 c.d.m., rather strongly punctate, forming longitudinal undulate lines. Length of valve about 4 c.d.m. Breadth, 1*5 c.d.m. Marine. — Scotland, Ireland (Gregory !) Several species of Stanroneis of English authors do not belong to this genus, such as St. dubia Greg. I which is Achnanthes Hungarica Grun. ! ; St. ovalis Greg. ! which is Achnanthes ovalis {Greg.) H. V.H. ; St.dilatata W. Sm. which is Navicula crucicula IV. Sm. ; St. punctata W.Sm. which is Navicula punctata W. Sm. M 162 NAVICULA. GENUS 7.— NAVICULA BORY, 1822. Frustules free or enclosed in tubes, rarely united in a chain. Valve with three nodules in a straight line ; raphe straight. . Endochrome divided into two layers, resting on each of the sides of the zone, with two lines of separation on the valves. ^,J\ -JEE Fig. 32. — Navicula Lyra Ehr Fig. 31. — Navicula nobilis Ehr. The figures here given are two type forms of Navicula : the N. nobilis and the N. lyra. In the Monograph, in course of publication by Prof. Cleve, descriptions of all known forms of this immense genus will be found. Mr. Cleve has subdivided it into various sub-genera. As the groups which we proposed in our Synopsis are very convenient for determination, and have also been adopted in some important works, including the Sylloge of Prof. De Toni, we prefer to retain them here. >s v ! L NAVICULA. i6- A. — True Naviculse. Frustules free, not enclosed in gelatino- mucous fronds. Sub-genus I. — Navicula. Analysis of Groups. I. — Valves without distinct puncta, furnished with costae (canaliculi) or robust strire, having the appearance of costae ; never didymous in form. True costre, not resolvable into beads . . . 1. Pinnularise. Striae robust, having the appearance of costae but resolvable into beads; strice radiate, almost or quite reaching to the raphe . . .2. Radiosse. II. — Valves with very distinct puncta or fine striae having no semblance to costae or with costae ; or again with costae alternating with rows of beads. a. Valves wit/i strne interrupted by two sulci near the raphe. { ( Valves more or less constricted in the Sulci not j median portion Sulci straight. -| lvre-shaped. \ yaives without constriction in the median I portion .... I Sulci lyre-shaped ...... L Sulci very broad and occupying the greater portion of the valv^ b. Valves more or less lanceolate, or elliptic or linear lancvlate, without any sulcus. 3. Didymse. 4. Ellipticse. 5. Lyratse. (J. Hennedyjse. f 3 O cj 'a, in c o .2 Valves having the appear- f Valves having the appearance of a ance of a stauros, either | grater, with very large, elongated by the absence of striae or -{ beads .... by the space between j them . . . t Valves with tine striae . Striae leaving a con- siderable hyaline Valves without any appear- ance of stauros. Valves with puncta not forming longitu- dinal lines in zig-zag. Striae with beads not forming longitu- dinal lines. Striae with beads forming longitu- dinal and trans- verse lines. Hyaline space very elongate and in- finitesimally di- minuate . ! space round the raphe and central nodule. Beads extending over the whole valve .... Hyaline space rounded and abruptly diminu- ate 7. Asperse. 8. Stauroneidese. 9. Palpebrales. 10. Abbreviate. 11. Perstriatse. Valve very elongate, linear . Valve lanceolate . almost 12. 13. Johnsoniese. Crassinerves. Valves with puncta forming longitu- dinal lines in zig-zag. Striation almost invisible with the best objectives, valve linear lanceolate ^ simulating an Amphipleura ....... Zig-zags interrupted by pale places where the valve is depressed . . . .14. Sculptese. Lines in zig-zag, regular, not interrupted . 15. Serian'eEe. \3bis. Fusiformes. 164 NAVICULA. Valves not 1 inear. c. Valves having one or more narrow marginal or sub-marginal sulci. ( Valves lanceolate, large ; striae radiate, fine, leaving a large blank space round the centre nodule . . .16. Formosa?. Valves elongate, generally more or less tri-undulate ; sulcus marginal often inconspicuous ; raphe surrounded by a hyaline space lanceolate, narrow ; striae radiate . . 17. Limosse. Striae sub-parallel, often slightly oblique in reference to the longitudinal axis of the valve ; sulcus broad, very L conspicuous . . . . . . .18. Affines. Valves linear ; striae fine, sub-parallel ; sulcus very conspicuous ; terminal (, nodules elongate, distorted . . . . . . .10. Lineares. d. Valves more or less linear, without any sulcus. Striae radiate, occupying only the margin of the valves Striae generally bent, reaching the raphe ; valves with smooth, thickened . 20. Americana?. apices ....... Very small navicular with hardly visible structure. . 21. Bacillese. 22. Minutissimse. I. Pinnulariae. a. Striatum not interrupted by a marginal sulcus. * Majores. — -Valves regularly elliptic-linear, often slightly inflated at the median portion and at the apices. Size usually large ; costae usually broad and robust. ANALYSIS OF SPECIES. Costae very distant from raphe ; size very con- siderable . . ■ . • N. nobilis. Not con- f Valve stricted not in girdle showing view; a hyaline fresh band, water forming species. a false stauros. Costae f rather approxi- mate to \ raphe ; size medium. [_ Valve showinsr a hvaline band in the form of a false stauros . N. cardinalis. Valve inflated at the median portion . N. major. Valve not inflated at the median portion N. viridis. Strongly ' con- Valve stricted without in girdle false view ; stauros marine species. - f Raphe bent like a brace, showing in girdle view- longitudinal hyaline spaces . . N. Trevelyana. I Valve showing a false stauros. Raphe straight in the middle of the valve ; girdle face without hyaline spaces N. 1 ectangnlata. f Striae very oblique, reaching ihe raphe everywhere . . . N. cruciformis. I Striae parallel, perpendicular to the raphe . N. quadratarea. N. nobilis Ehr. (Abh. 1840, p. 20, H.v.H Atl., pi. 5, f. 2* ; Type No. 52), plate 2, fig. 67. Valve linear-elliptic, inflated in the median portion and at the apices with coarse costae, considerably distant from the raphe. Girdle face linear with rounded angles. Costae radiate, very robust, 5 or 6 in 1 c.d.m. Length, 20 to 40 c.d.m. Fresh water. — Antwerp; probably not very rare. England, etc. NAVICULA. 165 Var. Dactylus. (N. Dactylus E/ir., H.V.H. Atl., pi. 5, f. 1*; Type No. 51), plate 2, fig. 68. More robust than the preceding, with inflations absent or only slightly marked ; costse generally not so long and more robust, about 4*5 to 1 c.d.m. Fresh water. — Heyst (J. Deby). Var. gentilis (N. gentilis Donk.,m H.V.H.'s Typ. Syn., Nos. 53 and 481). Absolutely similar to N. nobilis, but much smaller in all parts ; it may be considered as a dwarf form of N. nobilis. Length. 14 to 20 c.d.m. ; costal about 7 in 1 c.d.m. Fresh water and fossil deposits.— England, Scotland, Lough Mourne (Ireland), etc. N. major Kutz. (Baa, pi. 4, f. 19 ; H.V.H. Atl, pi. 5, f. 3-4* ; Type No. 54), plate 2, fig. 69. Valve linear-elliptic, more or less inflated in the median portion, apices not inflated, somewhat conical. Costre robust, 5 to 7 in 1 c.d.m., feebly radiate, rather approximate to raphe, and leaving an oblong hyaline space round the central nodule. Length, 18 to 30 c.d.m. Fresh water. — Everywhere. The Navicula major passes imperceptibly into the following : N. viridis Kutz. (Baa, pi. 4, f. 18; h.v.h. Atl, pi. 5, f. 5*; Type No. 56), plate 2, fig. 70. Valve linear-elliptic, without inflations, apices rounded. Costae about 7 in 1 c.d.m., rather approximate to the raphe, and leaving scarcely any marked space round the central nodule ; radiate at the middle of the valve, convergent towards the apices. Length, very variable, from 5 to 20 c.d.m. Fresh water. — Everywhere. Var. commutata Grun. {Nav. Jiemipieni and. ncc Kutz. — H.V.H. Atl., pi. 5, f. 6*; Type No. 57), plate 2, fig. 71. Valve elliptic-linear, considerably attenuated at the apices ; costs slender, attenuated round the central nodule, about n in 1 c.d.m. The two valves are dissimilar : one has striae covering the whole valve ; in the other the striae are interrupted (see the figure) unilaterally, near the central nodule. Length, about 4 to 6 c.d.m. Fresh water. — Manage (P. Gautier). N. cardinalis Ehr. (Americ.L, r,w> nW, 21, Ii.V.H. Atl. Supp., f. 5* ; Type No. 60), plate 2, fig. 72. 1 65 NAVICULA. Valve linear-elliptic, sometimes feebly inflated at the median portion, apices broadly rounded, sometimes somewhat inflated. Raphe surrounded by a broad hyaline zone, dilated round the central nodule ; costae robust, absent in the centre of the valve, where their absence forms a broad false stauros, gently radiate near the central nodule, convergent at the apices of the valve, about 5 in i c.d.m. Length, 15 to 20 c.d.m. Fresh water. — Botanical Gardens at Brussels (Delogne). England, Ireland, France, Holland, Germany, Norway, Sweden, etc. N. Trevelyana Donk. (Q.j.m.s. 1861, n.s. i, p. 8, pi. i, f. 2 ; H.V.H. Atl. Supp., f. 5 and 6*; Type No. 72), plate 2, fig. 73. Valve linear, gently inflated at the median portion and at the apices all are broadly rounded. Raphe curved with a brace, surrounded by a narrow hyaline zone, broadly dilated round the central nodule ; costae well marked, n in 1 c.d.m., very radiate at the central portion, very convergent at the apex of the valve. Girdle face broad, very constricted at the median portion, with truncate apices. Striae interrupted between the nodule and the apex of the valve by a smooth space, parallel to the connecting membrane ; smooth spaces very conspicuous in girdle view, slightly visible at the edges of the valve in valve view. Length, 10 to 13 c.d.m. Marine. — Blankenberghe : washing of sand from shore. England, France, Denmark, Norway, etc. N. rectangulata Greg. (d. of Clyde, p. 7, pi. i, f. 7; H.V.H. Atl. Supp , f. 7* ; Type No. 74) ; plate 2, fig. 74. Valve linear, with apices broadly rounded, inflated at the median portion and at the apices. Raphe bordered by a narrow hyaline zone, somewhat dilated round the central nodule. Striae distant, 8 or 9 in 1 c.d.m., very radiate at the median portion, very convergent towards the apex of the valve. Girdle face oblong, constricted at the median portion, with truncate apices. Length, about 6 to 7 c.d.m. Marine — Blankenberghe, in the sand of the shore. England, Scotland, France, Denmark. Var. Stauntonei Grun. (Alloioneis Staunionei Gru?i., in CI. and Moll. Diat. No. 304). Marine. — England (Firth of Tay, Rattray). N. cruciformis Donk. (q.j.m.s. 1861, n. s. i, p. 10, pi. i, f. 7 ; H.V.H. Atl. Supp., f. 8* j in Type No. 74) plate 2, fig. 75. Valve linear, with apices rounded, not inflated, median portion sometimes very slightly inflated. Raphe not bordered by a hyaline zone/ central nodule NAVICULA. 167 surrounded by a broad, cuneate pseudo-stauros ; striae flexuous 12 to 13 in t c.d.m., very radiate near the central nodule ; very convergent at the apex of the valve. Girdle view constricted at the median portion, with truncate apices. Length 5 to 12 c.d.m. Marine. — Blankenberghe, in the sand of the shore. England, Norway. N. quadratarea Ad. Schm. (Nordsee, p. 90, pi. 2, f. 26*; JV. pinnularia C/., Sv. o. Norsk. Diat., p. 224, pi. 1, f. 1-2), plate 25, fig. 7°4- Valve linear-oblong, with rounded apices; stria; parallel, 9 or 10 in 1 c.d.m,, reaching to the raphe, and leaving round the central nodule a broad quadrangular stauroform hyaline space. Length, about 9 c.d.m. ; breadth, 1*25 c.d.m. Marine. — North Sea (coasts of Ireland and Scandinavia). i 68 NAVICULA. **Minores. — Frustules of medium or small size, with valves of variable form, rarely regularly linear, often inflated at the median portion and diminuate at the apices ; costae medium or narrow. I. — Terminal nodules not laterally dilated like a hook. a. — Valves neither undulate nor constricted in the middle. ANALYSIS OF SPECIES. r Costa; very robust and very dis- tant. With- out any false stauros. f Costas dis- Valve sublinear, abruptly inflated in the tant i middle . . . . . N. j from j the Valve broadly lanceolate . . . N. I raphe. l_ lata, alpina. Costas reaching nearly to the raphe, valve sublinear . N. borealis. Costa: ap- proxi- mate. With a false ■ stauros. Costas ap- proxi- mate to raphe not per- ceptibly short- ened towards the central nodule. I f Valve very large, with obtuse apices, costas not resolvable . . . . . . N. divergens. Valve very small, apices acute, costas resolvable with N. costulata.* L difficulty ...... f Valve r with- Valve slightly inflated at the median por- out a tion ; costs; very fine ; fresh water staur- ! species . . . . . N. sublinearis. onei- '[ form Valve linear, not inflated, costa; rather blank robust ; marine species . . . N. retusa. space. l_ Valve with stauroneiform blank space, apices rostrate-capitate . . . . . N. Hilseana. Costas often approxi- mate to the raphe, and im- per- ceptibly short- ened towards the central nodule. Valves in- flated at the me- dian por- tion only slight- ly or not at all. Apices somewhat diminuate . N. Brebissonii. f Valves scarcely in- flated in the middle N. stauroptera. Apices not ros- trate capi- tate. Apices in- flated. Valves con- sider- ably in- flated at the me- dian por- tion. Median in- fl a t i o n abruptly diminuate Media n i nflation diminish- in g im- percep- tibly up to' the apices N. Tabelleria. Apices more or less ros- trate- capi- tate. Valve exactly linear ; apices strongly rostrate-capitate ; no pseudo stauros Valve somewhat inflated with subcapitate apices ; costas rather distant ; a false stauros Valve somewhat inflated, apices subcapitate ; costas approxi- mate ; a false stauros. Valves con- sider- ably in- flated at the me- dian por- tion. Valve linear-oblong, with apices broadly rostrate-capitate . N. gibba. N. bicapitata. N. subcapitata. N. appendiculata. N. globiceps. Valve linear-lanceolate, with apices to an average extent rostrate-capitate . . N. Braunii. NAVICULA. 169 b. Valves undulate or constricted. f Valve rather broad, with median f Apices strongly rostrate-capitate . N. mesolepta. inflation not much larger than -j the terminal. ^ Apices scarcely diminuate-rostrate . N. Legumen. : Median inflation much larger than the terminal inflations; valve very narrow N. polyonca. Median inflation much smaller than the terminal inflations . . . N. claviculus. II, — Terminal nodules dilated laterally like a hook. Valve very inflated at the median portion, apices subcapitate costae very robust. ......... N. bumilis.* b' . Striation interrupted by a marginal sulcus. f Striae not reaching to the raphe and leaving a large hyaline space round the central nodule . . . . . . . . N. blanda. j Strice reaching everywhere to the raphe and central nodule . . . N. sejuncta. * For facility in determination we have left, in the Table of the Pinnularieae, the ;V. costulala and Ar. humilis, which belong to the Radioseae, but are very difficult to resolve into beads. See these species among the Radiosea-. i. Valves neither undulate nor constricted in the middle. A.— Costae very distant and very robust. * WITHOUT A FALSE STAUROS. N. lata Breb. ! (W. Sm., S.B.D. 55, sub. Pinnularia, pi. 18, f. '67 . H.V.H. Ad, pi. 6, f. 1, 2*; Type No. 61), plate 2, fig. 76. Valve linear, with median portion slightly inflated, apices obtuse, broadly rounded. Costae very robust, distant, 4 to 5 in i c.d.m., not reaching to the raphe, and leaving a dilated hyaline space round the central nodule ; costae feebly radiate at the middle of the valve, and changing direction imperceptibly towards the apices. Length, about 6 to 1 1 c.d.m. Fresh water in mountainous regions.— Not yet found in Belgium. England, France. N. alpina Ralfs. (in Pritch. Inf., p. 906; W. Sm. S.B.D. i., p. 55, pi. iS, f. 168* ; H.V.H. Type de Syn. No. 51), plate 25, fig. 705. Valve broadly lanceolate-elliptic, with apices obtuse. Costae very robust, distant, radiate, 2-5 to 3 in 1 c.d.m., resting very distant from the raphe, and not symmetrically on each side of the valve. Raphe and nodules very robust. Girdle face quadrangular, elongate, showing on the connecting membrane two distant lines of fine elongate puncta. Length of valve, 10 to 20 c.d.m. Fresh water of subalpine regions. — Scotland, France. 170 NAVICULA. N. borealis Ehr. (Verb. pi. I., II, f. 6 ; H.V.H. Atl., P. 6, f. 3*; Type No. 62), plate 2, fig 77. Valves linear-elliptic, sometimes feebly attenuated at the apices which are rounded or subtruncate. Costae rather robust, distant, about 5 or 6 in t c.d.m., and reaching almost to the raphe, except those in the middle, which are shorter ; costge radiate at the median portion of the valve, becoming imper- ceptibly convergent towards the apices. Length, 3 to 6 c.d.m. Freshwater. — Antwerp; Frahan (Del.); probably not rare. Often found in mosses growing on rocks and humid walls. Found throughout Europe. This type form is connected with N. lata by various intermediate forms, such as N. lata Tar. minor Greg. ; N. Rabenhorstii Gru/i., etc. These forms will be found in H.V.H. 's Types of Syn. No. 63, collected by Mr. Delogne at Frahan. WITH A FALSE STAUROS. N. divergens W. Sm. ! (S.b.d. i.,P. 57, pi. 18, f. i77*inH.v.H.'s Types of Syn. Nos. 5 1 and 484), plate 25, fig. 706. Valve narrowly lanceolate, with apices somewhat attenuated. Costse robust, about 5 in 1 c.d.m., not reaching to the raphe, radiate at median portion, convergent towards the apices, leaving near the central nodule a broad stauro- form blank space. Length of valve, 7 to 16 c.d.m. Breadth 1.5 to 2.5 c.d.m. Fresh water. — Ard. Liege (De Wild.), England, Scotland, France, Gottland, etc. B. — Costae approximate. a. COST.F. REACHING THE RAPHE THROUGHOUT AND SLIGHTLY SHORTENED NEAR THE CENTRAL NODULE. N. sublinearis Grun. (H.v.H. Atl, pi. 6, f. 25 and 26*) plate 2, fig. 78. Valve narrow, linear, sometimes somewhat inflated at the median portion, with rounded apices. Costa; reaching to the raphe, those round the central nodule slightly shortened ; costa; fine, radiate in the middle of the valve, becoming convergent by imperceptible degrees towards the apices, 21 to 24 in 1 c.d.m. Length, 2 to 3 c.d.m. Fresh water. — Not yet found in Belgium. N. retusa Breb. (Diat. Cherb. pi. 16, f. 6.— H.V.H. Atl. Supp.,f. 9*, in Type No. 168) plate 2, fig. 79. Valve linear-oblong with rounded apices. Raphe bordered by a narrow hyaline zone, slightly dilated round the central nodule. Costa; robust, distant, NAVICULA. 171 with apices somewhat capitate, feebly radiate, 8 in 1 c.d.m. Girdle face contracted, apices truncate. Length, about 7 c.d.m. Marin.e — Not yet found in Belgium, England, Ireland and Fiance. Var. subretusa. (N. subretusa Grun! in Type No. 74. H.V.H. Atl. Supp., f. 10*, in Type No. 74) plate 2, fig. 80. Valves narrow ; 6 striae in 1 c.d.m., with non-capitate apices. Length, about 7 c.d.m. Marine. — Blankenberghe, in the sand of the shore. N. Hilseana Janisch. (in Schmidt. Atl., pi. 45, f. 65, etc. H.V.H. Atl., Supp., f. ir,* in Types Nos. 39 and 347) plate 2, fig. 81. Valve linear, with rostrate-capitate apices. Raphe without hyaline zone ; Central nodule surrounded by a pseudo-stauros rather broad, sub-cuneate. Striae rather feeble 10 in 1 c.d.m. ; radiate in the centre, convergent at the apex of the valve. Length, about 4 c.d.m. Fresh \vater.--Paliseul (Delogne). aa. COST/E NOT REACHING THE RAPHE THROUGHOUT, THOSE IN THE MIDDLE OF THE VALVE CONSIDERABLY SHORTENED OR ABSENT. b. Valves o?dy slightly or not inflated at the median portion. N. Brebissonii Kiitz. ! (Bac. p. 93, pi. 3, f. 49; H.v.H. Atl, pi. 5, f. 7* ; Type No. 58) plate 2, fig. 82. Valve linear-elliptic, with apices rounded, somewhat diminuate. Raphe surrounded by a hyaline zone, narrow towards the apices, infmitesimally dilated towards the median portion. Costae well marked, shortened towards the median portion and absent in the middle of the valve, where their absence forms a false stauros ; costae rather strongly radiate up to nearly the extreme third of the valve where they suddenly become strongly convergent, 11 in 1 c.d.m. Length, 4 to 5 c.d.m. Fresh water. — Common throughout Europe. Var. subproducta. (H.V.H. Atl., pi. 5, f. 9*), plate 2, fig. 83. Broader and shorter, with apices somewhat diminuate sub-rostrate. Park, near Louvain. Var. diminuta. (H.V.H., pi. 5, f. 8*), plate 2, fig. 84. Slender, very small, apices infmitesimally diminuate. Frahan (Delogne). N. Stauroptera Grun. (ijber neue etc. fam. Navicula, p. 517. H.V.H. Atl., pi. 6, f. 7*) plate 2, fig. 85. Valve linear-elongate, scarcely inflated at the median portion, with apices rounded, inflated. Costae radiate at the median portion, strongly convergent at apices ; robust, leaving throughout a considerable hyaline 172 NAVICULA. space round the raphe, diminishing in length on nearing the central nodule around which they are completely absent, thus producing a pseudo- stauros ; about 10 to 12 in 1 c.d.m. Length of valve, about ioc.d.m. Fresh water. — Eegenhoven near Louvain (P. Gaut. ), etc., France. Var. parva. (Stauroptera parva Ehr. H.V.H. Atl. pi. 6, f. 6*) plate 2, fig. 86. Distinguished from the preceding by its smaller size (about 6 to 7 c.d.m.) and its median portion being more inflated. Ditches near Nieuport (Westendorp and Wallays according to Rabenhorst : Fl. Eur. Alg. , p. 222). N. Tabellaria Ehr. (Verb., p. 134, pi. II i., f. 26 ; Kiitz. Bac. p. 98, pi. 28, f. 79 ; H.V.H. Atl., pi. 6, f. 8*), plate 2. fig. 87. Differs from the preceding by the terminal and median inflations being much more marked, by the costse occupying all or nearly all the valve, but reduced almost to dots at the exact median portion, their number being more considerable, 12 to 15 in 1 c.d.m., and lastly by its more considerable size, which attains to 14 c.d.m. The terminal costse have been designated radiate in error, — they are con- vergent, as in the preceding species. Fresh water. — Eegenhoven near Louvain (P. Gaut.). England, France. Mixed with the preceding and the following. Var. stauroneiformis. — Median strife entirely absent. N. gibba KutZ. (Bac. pi. 28, f. 70 ; H.V.H. Atl. Supp., f. 12*, .Type No. 64), plate 2, fig. 88. Differs from the preceding by the median inflation, which is prolonged, while infmitesimally diminishing up to the terminal inflations. Costse about 12 in 1 c.d.m., sometimes absent in the median portion. Length, 5 to 7 c.d.m. Fresh water. — Eegenhoven near Louvain (P. Gaut.). Found throughout Europe. Var. brevistriata. (H.V.H. Atl., pi. 6, f. 5*), plate 2, fig. 89. Costse very short, occupying only the margins of the valve. Mixed with the type form. N. bicapitata Lagerstedt. (D. from Spitsb , n. 6, p. 23 ; H.V.H. Atl., pi. 6, f. 14*), plate 2, fig. 90. Valve narrow, linear, with apices attenuated, rostrate-capitate ; costse rather fine, 9 to 10 in 1 c.d.m., radiate in the middle of the valve, convergent at the apices, leaving round the raphe a narrow hyaline zone, which expands into a sub-quadrangular area round the central nodule. Length, about 6 c.d.m. Fresh water. — Not yet found in Belgium. England, Ireland. NAVICULA. I 73 N. subcapitata Greg. (Q.J. M.S. 1856, p. 9, pi. 1, f. 30, h.v.h. Atl., pi. 6, f. 22*), plate 2, fig. 91. Valve very narrow, linear, somewhat attenuated at the median portion, with apices rostrate, gently sub-capitate; costae rather distant, about u to 12 in 1 c.d.m., not reaching to the raphe, and absent in the middle of the valve ; terminal nodules rather large. Length about 2*5 to 3*5 c.d.m. Freshwater. — Noire-fontaine (Delogne) ; Manage (P. Gaut.) ; England, Ireland. Var. paucistriata. (H.V.H. Atl., pi. 6, f. 23*), plate 2, fig. 92. Striae short, diminishing gradually in length, and absent on all the median portion of the valve. N. appendiculata Kutz. (Baa, p. 93, pi. 3, f. 18; pi. 4, f. 1, 2; pi. 5, f. 5 ; H.V.H. Atl., pi. 6, f. iS and 20*), plate 2, fig. 93. Valve narrow, linear, very feebly attenuate at the median portion, with apices feebly rostrate-subcapitate ; costae delicate, 16 or 17 in 1 c.d.m., not reaching to the raphe, radiate at the median portion of the valve, where they are gradually shortened, so as to leave a large stauronei- form hyaline space, convergent at the apices. Length, 2*5 to 3*5 c.d.m. Fresh water. — Brussels Botanical Gardens (Del.). Found throughout Europe. bb. Valves considerably inflated at the median portion . N. globiceps Greg.! (Q.j.m.s. 1856, iv., p. 10, pi. r, f. 34; H.V.H. Atl. Supp., f. 13* in Type No. 284), plate 2, fig. 94. Small, linear-oblong, inflated at the median portion with apices broadly rostrate-capitate. Costae not reaching to the raphe, leaving a large hyaline space round the central nodule, 16 to 18 in 1 c.d.m.; the median ones very radiate, the terminal convergent ; central nodule large. Length, 3 to 4 c.d.m. Fresh water. — Rare. Antwerp in the Schyn, etc. Canal d' Herenthals. Scotland (Greg !). N. Braunii Grun. ! H.V.H. Atl., pi. 6, f. 21*), plate 2, fig- 95- Linear-lanceolate, with apices to an average degree rostrate-capitate. Costae not reaching to the raphe, 10 or 11 in 1 c.d.m.; the median ones strongly radiate, the terminal convergent, gradually shortened up to nearly the middle of the valve, where they leave a broad stauroneiform hyaline space; central nodule narrow. Length, 4 c.d.m. Fresh water. — Liresse (Delogne). 174 NAVICULA. 2. Valves bi-undulate or tri-undulate, or conspicuously constricted in the median portion. N. mesolepta Ehr. (Am. iv., n. 4W; h.v.h. Atl., pi. 6, f. io and ii*; Type No. 68), plate 2, fig. 96. Valve linear-oblong, tri-undulate, with apices rostrate-capitate ; striae gradually shortened towards the central nodule, the median ones very radiate, the terminal convergent, 10 to 14 in 1 c.d.m. Length, 3 to 6 c.d.m. Fresh water. — Almost everywhere. Var. Termes (N. Termes, Ehr., H.V.H. Atl., pi. 6, f. 12, 13*), plate 2, fig 97. Valve with median inflation replaced by a slight constriction ; striae absent in the middle of valve, thus forming a pseudo-stauros. Fresh water. — Antwerp, Louvain, etc. (H.V.H. ), Ard Liege (De. Wild), N. Legumen Ehr. (Mikrog, various figures— H.V.H., pi. 6, f. 16* ; Type No. 69), plate 2, fig. 98. Valve linear, gently tri-undulate, with undulations sometimes scarcely noticeable ; apices diminuate-rostrate, scarcely capitate ; raphe surrounded by a broad hyaline area, considerably dilated round the central nodule ; striae about 11 in 1 c.d.m., very radiate at the median portion, very convergent towards the apices of the valve. Length, 8 to 10 c.d.m. Fresh water. — Liresse (Delogne). Found throughout Europe. N. polyonca Breb. ! (in Kiitz. Sp. Aig., p. 85 ; h.v.h. Atl. Supp., f. 14*), plate 2, fig. 99. Valve linear-narrow, tri-undulate, with median inflation much stronger than the others ; apices strongly inflated-capitate ; raphe surrounded by a large hyaline zone, which widens into a false stauros at the median portion; striae about 12 in 1 c.d.m., shortened at the median portion where they are radiate, becoming very convergent at the apices. Length, 6 to 8 c.d.m. Fresh water.— Rare. Liresse (Delogne), Scotland, Ireland, France. N. claviculus Greg. (Diat. of Clyde, p. 6, pi. 1, f. 5*), plate 25, fig- 7°9- Valve sublinear-narrow, feebly inflated at the median portion, more strongly inflated from and after the median portion, and this up to the apices which are rounded obtuse. Striae not reaching to the raphe ; only slightly or not radiate, about 14 in 1 c.d.m ; absent at the median inflation. Length of valve, 3-5 to 5 c.d.m. Breadth, about 1 c.d.m. Marine. — Scotland, Ireland, Jutland, Bahusie. NAVICULA. T75 B. — Striation interrupted by a marginal sulcus. N. blanda Ad. Schm. (Nordsee, p. 90, pi. 2, f. 27*; Pinnularia Ergadensis Greg., T.M.S., 1856, p. 48, p. 5, f. 22 ?) plate 25, fig. 707. Valves linear, with parallel or subparallel costae, apices rounded, leaving a considerable hyaline area round the central nodule and not reaching to the raphe, feebly radiant in the centre of the valve and somewhat convergent at the apices, 8 to 10 in 1 c.d.m., interrupted by a very conspicuous marginal sulcus. Length, 5 to 13 c.d.m. Breadth, 1 to 2 c.d.m. Marine. — North Sea, Hvidingsoe (Ad. Schm.) N. blanda which has been found in various regions of the globe appears to be very rare in the North Sea ; it belongs to a small group of forms of which N. Poivellii (not yet found on our shores) is the type form. N. sejuncta Ad. Sch . (Nordsee, p. 87, pi. 1, f. 18*) plate 25, fig. 708. This species, still imperfectly known, has also been found at Hvidingsoe but it is equally rare. This form is much smaller than the preceding and the stria; reach the raphe throughout. II. Radiosae. A . Terminal nodules approximate to apices of valves. I. Median striae radiate, terminal striae convergent. a. STRI.E APPROXIMATE. f Terminal stripe in broken lines f Median striae Striae in continuous lines. alternately long and short. Median stripe not alternately long and short. r Valve broadly lanceolate, not rostrate-capitate \ Valve broadly lanceolate, rostrate-capitate t Valve anceolate, very narrow ..... • Median striae equally shortened forming a pseudo-stauros ; striae near the central nodule almost straight N. oblonga N. peregi\na. N. salinarum. N. cincta. N. gracilis. Apices not rostrate- capitate. Apices not conspicuously diminuate-rostrate No false stauros Nodule surrounded by a considerable -{ hyaline area ; valve broadly | Apices conspicuously lanceolate. (_ diminuate-rostrate Hyaline area very small ; valve narrowly lanceolate ; median striae very radiate .... . N. vulpina. Apices rostrate- capitate. Striae robust. f Hyaline area dilated trans- versely, apices very robust . Hyaline area rounded, apices sub-obtuse Striae scarcely visible N. viridula. N. radiosa. N. cryptocephala. N. rhynchocepliala N. gregaria. ij6 NAVICULA. b. STRLE VERY DISTANT AND VERY ROBUST ; VERY SMALL FORMS WITH TERMINAL NODULES LIKE HOOKS. r Valve rhomboidal with acute apices ; median portion furnished with a broad pseudo-stauros . . . . . . . . N. costulata. '] Apices capitate ; no pseudo-stauros . . . . . . N. humilis. [_ Valve elliptic ; with obtuse apices, median stria; simulating a schizo-stauros N. nana. II. Median striae radiate, terminal striae perpendicular to the raphe (straight). . N. cancellata. , N. inflexa. f f Valves narrowly f Apices short, acute | Median striae of | linear or -J quite the -J linear-lanceolate. [_ Apices rather long, inflected same length. i_ Valves broadly lanceolate, robust forms . . . N. fortis. Median strire | alternately long -| and short. ( Valve rather narrowly lanceolate, with sub-obtuse apices ; hyaline area not stauroneiform ; striae with very delicate puncta . N. digito-radiata Valve broadly lanceolate or elliptic, with very obtuse apices; hyaline area stauroneiform; striae with strong puncta .... N. Reinhardtii. III. All the striae radiate. Striae very robust. Without any appearance of a false stauros. Valves lanceolate. f Valve broadly lanceolate, striae very distant . N. > Valve very narrowly lanceolate, striae approximate . N. I Striae fine f Valve with obtuse apices N. approximate j 10 to 12 in i j Valve with acute apices . N- c.d.m. L ' Valve with apices broadly rostrate, not Showing the capitate . . . . N. semblance of a false -J Valve with apices capitate . K. stauros. Valve with apices rostrate-acute . . N. f Apices somewhat constricted . . . . N. Valves oval-oblong, -j Apices diminuate, rostrate, not capitate . . . N. (_ Apices rostrate, sub capitate . . . . N. Valves with apices strongly rostrate, not capitate . . N- Valves linear. distans. longa. Solaris, lanceolata. Gastrum. Anglica. crucifera. Semen, cajitata. dicephala. apiculata. Valves neither rostrate nor capitate, but very gently inflated at the median portion, connecting zone very broad . N. Kiitzingiana. IV. All the striae perpendicular to the raphe. f Valve very long, narrow, lanceolate, striae 'very robust and very distant, girdle face narrow . . . . . . N. directa. j Valve short, rather narrowly lanceolate, striae fine, approximate, girdle face I equal to 3-4 times the breadth of the valves . N. Northumbrica. NAVICULA. 177 B. Terminal nodules distant from the apices. ( Valves with median longitudinal portion elevated and consequently appearing to be formed of two super- „ , •., posed valves . . . . N. superimposita. Valves with | ' *• *■ sides equal. | yaives wjth on]v tlle ap|ces elevated . . . N. compressicauda. L Valves flat . . N. opima. ,. , ... f Apices subacute . . . . N. Cesatii. V alves with J ^ sides unequal. ^ Apices rostrate-capitate . . . . . N. inaequilatera. A. Terminal nodules approximate to apices of valves. /. Median stricc radiate, terminal stria: convergent. A. Striae approximate. a. TERMINAL STRIDE IN BROKEN LINES. N. oblonga Kutz. (Baa, p. 97, pi. 4, f. 21; H.V.H. Atl, pi. 7, f. 1* ; Type No. 76), plate 3, fig. 100. Valve linear-elliptic, perceptibly inflated in the median portion, with apices very gently inflated-capitate. Raphe surrounded by a conspicuous hyaline zone dilated circularly round the central and terminal nodules. Costaj robust finely striate transversely, very distant round the central nodule (5 in 1 c.d.m.) then more compact (7 in 1 c.d.m.), radiate, flexuous, lastly the terminal ones still more approximate (8 in 1 c.d.m.), their lines of direction broken abruptly in the middle, radiate from the edge of the raphe, convergent from the edge of the margins. Terminal nodules very robust. Length, 15 to iS c.d.m. Fresh water. — Rather common and found throughout Europe. />. STRLE IN CONTINUOUS LINES. a. Median strice alternately long and short. N. peregrina (Ehr. ?) Kutz. (Baa, p. 97, pi. 28, f. 52 ; H.V.H. Atl., pi. 7, f. 2*; Type No. 77), plate 3, fig. 101. Valve broadly lanceolate, with apices very feebly diminuate-rostrate. Raphe surrounded by a narrow hyaline zone dilated round the central nodule, where the blank space forms more or less a square transversely elongate. Costae divided finely transversely, very robust; distant round the central nodule (5 or 6 in 1 c.d.m.) where the long striae are frequently mixed with one or two shorter strife ; median stria? very radiate (6 or 7 in 1 c.d.m.) the terminal ones very convergent, about 8 in 1 c.d.m. Terminal nodules rather robust. Length, 8 to 11 c.d.m. Brackish water. — Scheldt at Antwerp, and throughout Europe. N 178 NAVICULA. var. Meniscus Schum. (H.V.H. Atl., pi. 8, f. 19*), plate 3, fig. 102. Smaller, more broadly lanceolate, with apices diminishing more abruptly. Length, 4 to 7 c.d.m. Striae, 7 or 8 in 1 c.d.m. Brackish water. — Belgium, etc. var. Menisculus Schum. (H.V.H. Atl., pi. 8, f. 20, 21 and 22* ; in Type No. 190), plate 3, fig. 103. Very small, lanceolate-elliptic, infinitesimally attenuate towards the apices, or diminuate-rostrate. Hyaline space round the central nodule sometimes next to nothing. Striae, 8 to 12 in c.d.m. Length, 2-5 to 3 c.d.m. Fresh water. — Louvain (P.G.) id. forma Upsaliensis Grun. (H.V.H. All., pi. 8, f. 23, 24*), plate 3, rig- 104. More narrowly lanceolate, with apices more or less diminuate-rostrate. Striae delicate from 8 to 12 in c.d.m. Length, 3 to 4 c.d.m. Fresh water. — Louvain (P.G.) N. salinarun Grun. (Arct. Diat., p. 33, pi. 2, f. 34; H.v.H. Atl., pi. 8, f. 9* Type No. 95), plate 3, fig. 108. Valve broadly lanceolate, sub-elliptic, with apices strongly rostrate, and more or less capitate. Central nodule surrounded by a hyaline area very elongated longitudinally. Striae rather strongly divided crosswise 14 to 16 in 1 c.d.m., the median radiant, the terminal feebly convergent. Lengih, 2*5 to 3-5 c.d.m. Breadth, 1 to i'5 c.d.m. Brackish water. — Heyst (according to Deby) ; Antwerp (Scheldt, H.V.H.); Norfolk (England, Kitton). N. cincta (Ehr !) Kutz. (Mik., pi. x. 2, f. 6; H.V.H. Atl., pi. 7, f. 13-14*; Type No. 82), plate 3, fig. 105. Valve lanceolate, very narrow, with rounded obtuse apices ; central nodule surrounded by a hyaline area somewhat extended transversely; striae delicate, about 12 in 1 c.d.m., those round the central nodule much more distant. Length, about 4 c.d.m. Fresh and brackish water.— Aid. Lieg. (De Wild.). England. forma minuta. (H.V.H. Type No. 83); very small; Ostend. var. Heufleri Grun. (H.V.H. Atl., pi. 7, f. 12 and 15*), plate 3, fig. 106. _ Smaller with median hyaline space round, striae more robust and more distant, about 10 in 1 c.d.m. Length, about 2 to 2-5 c.d.m. Somewhat brackish water— Austruweel near Antwerp (P.G. ). NAVICULA. 179 var. leptocephala Breb. (H.V.H. Atl., pi. 7, f. 16*; Type No. 84), plate 3, fig. 107. Like the preceding variety, but still somewhat smaller. Valve with median portion somewhat inflated, with apices gently tapering sub- rostrate. Austruweel near Antwerp (H.V. H.). b. Median stria: not alternately long and short, a'. Median Stri.e equally shortened, forming a pseudo-stauros ; the STRI.T. NEAR THE CENTRAL NODULE ALMOST STRAIGHT. N. gracilis KlltZ (Baa, p. 91, pi. 3, f. 48; H.V.H. Atl, pi. 7, f. 7-8*; Type No. 81), plate 3, fig. 109. Valve elongate, narrowly lanceolate, with the portion quite terminal, some- times very gently produced, somewhat acute ; striae robust, the 2 or 3 close to the central nodule equally shortened ; the median scarcely radiant, almost straight ; the terminal convergent ; on an average 10 in 1 c.d.m., all reaching to the raphe. Length, 4 to 8 c.d.m. Fresh water — Antwerp, etc. (H.V.H.), Aid. Lieg. (De Wild.). Found throughout Europe. var. schizonemoides H. Van Heurck. (S. neglectum Thwaites — H.V.H. Atl., pi. 7, f. 9-10*) plate 3, fig. no. Valve usually somewhat narrower near to apices ; median striae longer and of unequal length. Frustules included in mucous tubes. Fresh water.— Louvain (P. G. ), &c. Bristol, England (Thwaites). a' a'. Without false stauros. * Alices not rostrate-capitate. N. vulpina KlltZ. (Baa, p. 92, pi. 3, f. 43 (?) ; H.V.H. Atl., pi. 7, f. 18*; in Type No. 132), plate 3, fig. in. Large, valve broadly lanceolate, with apices gently produced, rostrate. Central nodule surrounded by a broad hyaline area, sub-quadrangular, rounded. Striae reaching to the raphe, robust, the median ones bent, radiant, the terminal convergent, average number 10 in 1 c.d.m.. Length, about 9 c.d.m. Freshwater. — Ard. Lieg. (DeWild.). Finnety, Scotland. N. viridula Kutz. (Baa, pi. 30, f. 47; H.V.H. Atl., pi. 7, f. 25* ; in Type No. 36), plate 3, fig. 115. l8o NAVICULA. Valve broadly lanceolate, with apices tapering, rostrate, obtuse. Central nodule surrounded by a broad rounded hyaline area. Striae robust, reaching to the raphe, the median ones radiant, about 8 in i c.d.m. ; the terminal convergent, 10 in i c.d.m. ; terminal nodules robust. Length, about 7 c.d.m. Fresh water. — Brussels (Delogne). Throughout Europe. forma minor.— H.V.H. At!., pi. 7, f. 26*), plate 3, fig. 116. Smaller with more rostrate apices. var. avenacea. (N. avenaaa Breb. ; H.V.H. Atl., pi. 7, f. 27*; Type No. 8S), plate 3, fig. 117. More lanceolate ; apices more narrowly rostrate. Length, about 5 c.d.m. Fresh water.— Brussels (Del.). Ard. Lieg. (DeWilri.). Pentland Hills, Scotland. var. Slesvicensis (IV. Shsvicensis Gri/n.f); H.V.H. Atl., pi. 7, f. 28 and 29* ; Type No. 89), plate 3, fig. 118. Small, rather broadly lanceolate, apices conspicuously rostrate with a broad rostrum. Striation as in the type form, 8 or 9 stria? in 1 c.d.m. Breadth, 3 to 5 c.d.m. Fresh and brackish water. — Rather common. Antwerp (Scheldt), Louvain (P.G. ), &c. Stoneferry, near Hull, Duddington Lock, Northamptonshire (England). N. radiosa Kutz. (Baa, p. 91, pi. 4, f. 23; H.V.H., pi. 7, f. 20* ; Type No. 85), plate 3, fig. 112. Valve lanceolate, narrow, slightly attenuate, with apices very gently sub- capitate. Central noduie surrounded by a very small hyaline area. Median striae bent, very radiant, the terminal ones convergent; about n or 12 stria? in 1 c.d.m. Frustules, narrow in girdle view, with apices diminuate. Length, 4-5 to 6 c.d.m. Fresh water. — Common throughout Europe. var. acuta. (Pinnularia acuta, IV. Stn.; H.V.H. Atl., pi. 7, f. 19* Type No. 86) ; plate 3, fig. 113. More elongated, more narrowly lanceolate, and with apices more acute Length, about 8 to 9 c.d.m. Fresh water. — As the preceding form with which it is often mixed. Var. tenella. (Nav. tenel/a Breb.; H.V.H. Atl, pi. 7, f. 21 and 22*; in Type No. 107), plate 3, fig. 114. Differs from the type form in its size, being smaller, its apices more acute, and its striae more delicate and more approximate, 15 to 18 in 1 c.d.m. Fresh water. — Brussels, etc. N. cryptocephala Kutz. ! (Bac, pi. 3, f. 26; H.V.H. Atl., pi. 8, f. 1 and 5*; in Type No. 25; var. intermedia: Type No. 92; var exilis: Type No. 93), plate 3, fig. 122. NAVICULA. l8l Valve lanceolate, elongate, with apices rostrate, slightly capitate. Central nodule surrounded by a rounded hyaline area. Striae rather robust, with very feeble transverse divisions, radiant at the median portion of the valve, scarcely convergent at the apices, about 16 in i c.d.m. Length, 2*5 to 3*5 c.d.m. Breadth, about 0*5 c.d.m. Fresh and brackish water. — Antwerp (H.V.H.), Ard. Lit5g. (DeWild.). Throughout Europe. var. veneta. (Nav. veneta Killz. ! H.V.H. At]., pi. 8, f. 3 and 4*), plate 3, fig. 123. Smaller than the type form, with apices scarcely rostrate-capitate, stria? distant, about 14 in 1 c.d.m. Length, about 2-5 c.d.m. Breadth, about o'5 c.d.m. var. exilis. (H.V.H. Atl., pi. 8, f. 2*; Type No. 93), plate 3, fig. 124. Very short; rostrum scarcely marked. Fresh water. — Brussels. England. Constitutes the link with the following species. * * Apices extremely rostrate or rostrate-capitate. N. rhynchocephala Kutz. (H.V.H. Atl, pi. 7, f. 31*. Type No. 90), plate 3, fig. 119. Valve broadly lanceolate, with apices strongly acuminate-capitate. Central nodule surrounded by a rounded hyaline area. Striae robust, clearly divided transversely, very slightly shortened round the central nodule. The median ones radiant, the terminal feebly convergent, about 9 to 12 in 1 c.d.m. Length, about 5 to 6 c.d.m. Brackish water. — Antwerp. Found throughout Europe. var. amphiceros. (H.V.H. Atl., pi. 7, f. 30*), plate 3, fig. 120. More shortly lanceolate with apices strongly rostrate, feebly capitate. Striae 8 to 10 in 1 c.d.m. Brackish wattr. — Antwerp. var. rostellata. (iV. rostellaia Killz. ? H.V.H. Atl., pi. 7, f. 23 and 24*. Type No. 87), plate 3, fig. 121. Broadly lanceolate ; apices narrowly rostrate ; hyaline area surrounding the narrow central nodule. Striae rather robust, about ic or n in 1 c.d.m. Length 4 to 6 c.d.m. Brackish water. — Antwerp. Norfolk, England. N. gregaria Donkin. (Q.J.M.S., i86r, p. 10, pi. 1, f. 10*; N. cryptocephala IV. Sm. ; H.V.H. Atl., pi. 8, f. 12, 13, 14 and 15; Type No. 94), plate 3, fig. 125. 1 82 NAVICULA. Differs from the preceding species, of which perhaps it is only a variety, by its very feeble striae, sometimes scarcely visible and scarcely radiant, almost straight, about tS in 1 c.d.m. Length, about 2*5 c.d.m. Brackish w.iter. — Common : Antwerp (Austruweel), Blankenberghe. England. France. The apices are sometimes simply rostrate, scarcely capitate (Blankenberghe), sometimes strongly capitate (Antwerp). AA. Striae very distant and very robust, very small forms with terminal nodule like a hook. N. costulata Grun. ! (Arct D., p. 27 ; H.V.H. Atl. SuPP., f. 15* ; Type No. 71), plate 3, fig. 126. Small, rhomboidal lanceolate, costae reaching to the raphe, very robust, very distant (7 or 8 in 1 c.d.m.), strongly radiant at the median portion, convergent near the apices, 5 to 7 on each quarter of the valve ; absent at the median portion, where they leave a very broad stauroneiform hyaline space. Terminal nodules like hooks. Length, 1*25 to 1*5 c.d.m. Fresh water — Rouge-Cloitre (Delogne). N. humilis Donk. (Brit. Diat., p. 67, pi. 10, f. 7.— JV. inflata IV. Sm., nee Au/z.—H.V.R. Atl., pi. n, f. 23*; Type No. 70), plate 3, fig. 127. Valve linear, very inflated at the median portion, with apices rostrate capitate, truncate, rounded. Raphe not surrounded by a hyaline area. Costa? very robust, 8 in 1 c d.m., radiant at the median portion, convergent at the apices. Terminal nodules like hooks. Length, 1*5 to 2 c.d.m. Fresh water.— Common. Antwerp, Brussels (H.V.H. ), Aid. Li6g. (De Wild.), England. These two forms, which are very closely allied, have hitherto been mixed up with the Pinnulariae ; by examining them in the yellow medium of Prof. H. L. Smith, I have been able to demonstrate that they are clearly Radiosae, but with strise very difficult to resolve into beads. One figure is a little defective, there ought not to be a hyaline area round the central nodule. N. nana Greg.! (qj.m.S. 1856, iv., p. 3, pi. 1, f. 8), plate 25, fig. 711, after a photograph by H.V.H.* Valve minute, oval elliptic, with apices rounded, obtuse ; striae reaching almost to the raphe, very radiant ; the median ones simulating a schizo- NAVICULA. 183 stauros in consequence of their distance from one another, 10 or 11 in 1 c.d.m. Terminal nodules like hooks. Length of valve, 2 to 3 c.d.m. Breadth, 1 c.d.m. Fresh water. — Near Edinburgh, Scotland (Gregory !). II. Median stria: radiant, the terminal ones perpendicular to the raphe (straight). N. cancellata Donk. (Brit. Diat., p. 55, pi. 8, f. 4a and 4b. ; H.V.H. Atl. Supp., f. 16*; Type No. 73), plate 3, fig. 128. Valve narrow, linear or linear lanceolate, with apices tapering, acute or sub-acute. Raphe surrounded by a narrow hyaline zone, somewhat enlarged near the central nodule. Stria? very distant, 6 or 7 in 1 c.d.m.. faintly divided cross-wise, radiant at the median portion of the valve, perpendicular near the apices. Girdle face constricted in the middle. Length, 5-5 to 7 c.d.m. Marine. — Not yet found in Belgium. England, Scotland, Ireland, France. var. ammophila Grun. (Oest. Foss. Diat.. p. 14, pi. 2, f. 66-67*; in H.V.H. 's Types Nos. 1 1, 94, 116), plate 25, fig. 712. Small, narrow, striation approximate, 10 or 11 in 1 c.d.m. at the median portion, 12 or 13 at the apices. Length, 175 to 3 c.d.m. Marine and fresh water — Antwerp in Belgium. Creswell, Northumberland, England. var. Scaldensis H.V.H. (Atl. Supp., fig. 17*, in Type No. n), plate 3, fig. 129. Narrowly lanceolate, with apices attenuate-sub-rostrate. Striae 9 to 1 1 in 1 c.d.m. at the median portion of the valve. Length, 4-5 to 5*5 c.d.m. Brackish water — Antwerp. N. cancellata is not a true Radiosa. It ought to form, with allied forms, a special group, intermediate between the Pinnularise and the Radiosae. The same is true of JV. humids and cosiulata. N. crucifera Grun. ! (in Ad. Schm. Atl., pi. 46, f. 50-54*), plate 25, fig. 710. Valve lanceolate with apices cuneate, rostrate-acute. Transverse striae 5 or 5-5 in 1 c.d.m., distant, robust, finely divided cross-wise, not reaching to the raphe, all radiant ; the two median ones equally shortened and leaving an elongated stauroneiform hyaline space. Length of valve, 3 to 5-5 c.d.m. Breadth, about 1*5 c.d.m. Girdle face subquadrangular with somewhat con- 184 NAVICULA. cave sides, showing a smooth space at the apices. Connecting membrane smooth. Breadth of girdle face, 3*5 c.d.m. Marine — North Sea (?), Baltic Sea, etc. N. inflexa (Greg.) Ralfs. (in Pritch. Inf., p. 905 ; A. Schmidt's Atl., pi. 46, f- 69-7°*), plate 25, fig. 713. Very narrowly lanceolate, with apices sub-acute, inflexed. Striae, 10 in 1 c.d.m., distinctly punctate, radiate, reaching almost to the raphe, much shortened near the central nodule. Length of valve, about 3 to 5 c.d.m- Breadth, about 75 c.d.m. Marine — Scotland (Greg.), England (Donk.), Ireland (O'Meara). N. fortis Greg. (T.M.S., 1856, iv.,p. 46, pi. 5, f. 19, svb Pinnularia ; in Ad. Sch. Atl., pi. 46, f. 27*), plate 25, fig. 715. Valves oblong, with apices obtuse, rounded. Striae very robust, about 5 in 1 c.d.m., not reaching to the raphe, gently radiate in the median portion ; almost perpendicular at raphe, near the apices, leaving a hyaline area round the central nodule. Length, 8 c.d.m. Breadth, 2 c.d.m. Marine— Scotland (Greg. ), England (Donkin, Kitton), Ireland (O'Meara). A species not very well known. N. opima Grun. (Novara, p. 100, pi. ia, f. 13 ; Ad. Schm. Atl., pi. 46, f. 25-26*), plate 25, fig. 714. Valve elliptic or elliptic sublanceolate, with apices broadly lanceolate, terminal nodules considerably distant from the apices. Striae all radiant, distant, about 6 in 1 c.d.m., rather distant from the raphe and leaving a hyaline space, rounded, conspicuous, round the central nodule. Length, 5-5 to 9-5 c.d.m. Marine. — North Sea ; Baltic. N. digito-radiata Greg. (Q.j.M.S. 1856, p. 9, pi. 1, f. 32 ; H.V.H. Atl., pi. 7, f. 4* ; in Types 103, 260 and 261), plate 3, fig. 130. Valve narrowly lanceolate, with apices obtuse-rounded ; striae very delicately punctate, shortened round the central nodule, longer striae alter- nating with shorter, the median ones radiate, 8 in 1 c.d.m., the terminal almost straight, somewhat more compact. Brackish water. — Antwerp, Blankenberghe. England, and probably throughout all the coasts of the North Sea. NAV1CULA. 185 var. Cyprinus. (AT. Cyprinus IV. Sm., H.V.H. Atl., pi. 7, f. 3* j Type No. 78), plate 3, fig 131. Differs from the type form by the inflation in the median portion. Length, 6 to 8 c.d.m. Breadth in the median portion, 1*5 to 275 c.d.m. Marine. — Ostend (Deby) ; Blankenberghe (H.Y H.) ; England (frequent). N. Reinhardtii Grun. ! {Stauroneis Reinhardtii Grun., Nov., p. 566, pi. 4, f. 19 ; H.V.H. Atl., pi. 1, f. 5 and 6* ; Type No. 79), plate 3, fig. 132. Valve short, elliptic or lanceolate, with apices very obtuse-rounded, median portion abruptly inflated. Raphe surrounded by a narrow hyaline zone, dilated in form of stauros round the central nodule. Stria? surrounding the nodule alternately long and short, the median radiate, the terminal almost straight, all very strongly punctate, and about 9 in 1 c.d.m., except those in the neighbourhood of the nodule which are more distant. Length, 3-5 to 6 c.d.m. Breadth, about 1*5 c.d.m. Fresh water.— Rather common : Antwerp, Louvain, Brussels— probably England and other places. The preceding and the following forms are generally mixed together. var. gracilior Grun. (in H.V.H. Types du Syn. No. 71, A7! digtto- radiata var. striolata Grun. in Arc. D. ; Type No. 80.) Very similar to N. digito-radiata, from which it cannot be distinguished under a low magnification, but from which it is differentiated by its habitat and by the strongly punctate character of its stria?. Fresh water. — Rouge-Goitre (Delogne). 77/. Strice radiate up to the apices of the valves. N. distans (W. Sm.) H.V.H. {Pinnularia dislans IV. Sm., S.B.D., pi. 1, f. 56, pi. 18, f. 169 ; H.V.H. Atl. Supp., f. 18*), plate 3, fig. 133. Valve lanceolate, with sub-acute apices. Raphe placed in a sulcus, inflected on each side of the central nodule and forming round the raphe a broad hyaline zone. Central nodule surrounded (outside the sulcus) by a rounded hyaline zone. Stria? very robust and distant, about 4 in 1 c.d.m., radiate up to the apices of the valve. Length, 9 to 13 c.d.m. Marine. — Blankenberghe (very rare). England, and probably on all the coasts of the North Sea. N. longa Greg. (T.M.S., 1856, iv., p. 47, pi. 5, f. 18, sub. Pinnu- laria) ; Ad. Schm. Atl., pi. 47, fig. 6*), plate 25, fig. 716. Valve very narrowly lanceolate-subrhomboidal with subacute apices. Raphe surrounded by a very narrow hyaline zone. Stria? robust, radiate up to 1 86 NAVICULA. the apex of the valve, 4 or 5 in 1 c.d.m., leaving a small hyaline area round the central nodule. Length, 10 to 20 c.d.m. Breadth, about 1*5 c.d.m. Marine. — England, Scotland, Ireland, Denmark, Jutland. N. Solaris Greg. (T.M.S., 1856, iv., p. 43, pi. 5, f. 10*), plate 25, fig. 717. Valve elongate, narrowly lanceolate, with very obtuse apices. Striae 14 to 16 in 1 c.d.m., radiate up to the apices of the valve, resting rather distant from the raphe and leaving a considerable hyaline area round the central nodule. Length, 6 to 12 c.d.m. Breadth, 1 to 1-5 c.d.m. Marine— England, Scotland, Ireland, Denmark. N. lanceolata Kutz. ! (Baa, p. 94, pi. 30, f. 48 ; h.v.h. Ati, pi. 8, f. 16*; Type No. 96), plate 3, fig. 139. Valve lanceolate, with apices gently diminuate-rostrate ; striae shortened round the central nodule, radiate up to the apices of the valve, about 12 in 1 c.d.m. in the middle of the valve; 15 to 16 at the apices. Length, about 3 to 5 c.d.m. Breadth, about 1 c.d.m. Fresh water— Between Louvain and Parck (P.G.), Ard. Lieg (De Wild.). Throughout Europe. forma curta. (H.V.H. Atl., pi. 7, f. 17*), plate 3, fig. 140. Mixed with the preceding. var. phyllepta. (AT. phyllepta Kutz; H.V.H. Atl., pi. 8, f. 40*; Type No. 100), plate 3, fig. 141. Smaller than the type form, with stria? more delicale and much more compact, about 18 in 1 c.d.m. Brackish water — Blankenberghe. var. arenaria. (N. arenaria Donk., H.V.H. Atl., pi. 8, f. 18*; Type No. 97), plate 3, fig. 142. Much larger and more gradually attenuate than the type form. About 10 stria? in 1 c.d.m. Marine — Not yet found in Belgium. England (Donkin), Ireland (O'Meara), Scotland. N. Gastrum (Ehr.) Donk. (Br. Diat., p. 22, pi. 3, f. 10; H.V.H. Atl., pi. 8, f. 25, 27 and 32*), plate 3, fig. 134. Valve broadly elliptic with obtuse apices, broadly rounded, very gently constricted-subrostrate. Central nodule surrounded by a hyaline area, rounded or elongated transversely. Striae surrounding the nodule, alternately long and short. Striae finely divided transversely, radiate up to the apex of the valve, NAVICULA. 187 8 to 10 in 1 c.d.m. in the large forms, 12 to 14 in the small. Length, 2-5 to 4-5 c.d.m. Median breadth, 1.25 to 175 c.d.m. Fresh water.— Antwerp and probably elsewhere England (Kitton), Ireland (Donk. O'Meara), Scotland (Greg). var. Placentula. (A; Placentula Ehr., H.V.H. Atl., pi. 8, f. 26 and 28*), plate 3, fig. 135. Apices somewhat more inflated, striae 6 to 9 in 1 c.d.m., those surrounding the central nodule not alternately long and short. Brackish water — Antwerp (rather common). N. Anglica Ralfs. (in Pritch. Inf., p. 900, N. tumida W. Sm. ; H.V.H. Atl., pi. 8, f. 29*, in Type No. 59), plate 3, fig. 136. Does not differ essentially from the preceding species, to which it is closely connected, except that its apices are rostrate-capitate. Striae 10 to 12 in 1 c.d.m. Fresh water — England, Ireland. var. subsalina Grun. (H.V.H. Atl, pi. S, f. 31*), plate 3, fig. 137. Apices rostrate, scarcely somewhat capitate. N. crucifera Grun. See this form after N. cancellata, with which it is closely allied. N. Semen Ehr. (Verb. Amer., 1843, pi. IV. ii., f. 8; W. Sm., S.B.D., i., p. 50, pi. 16, f. 141*; H.V.H. Type No. 98) ; plate 25, fig. 718. Very variable in outline and size, in general very similar to N. gastruui, from which it differs in possessing an oval-oblong valve with apices somewhat constricted, very obtuse. Striae reaching throughout to the raphe and central nodule ; robust, finely divided transversely, all radiate, the terminal ones very approximate 9 to 10 in 1 c.d.m., the median, very distant, about 5 in 1 c.d.m. Length, 5 to 7 c.d.m. Breadth, at the median portion, 2 to 2-5 c.d.m. Fresh water — Belgium ? probable. England, France, Holland. Found in many fossil deposits. N. Capitata Ehr. (Inf., p. 185, n. 240, pi. 13, f. 20*; Schumann, 1862-69, f. 34*); plate 25, fig. 719 a.b. Valve small, oblong, inflected in the median portion, abruptly inflated at the apices, which are rostrate not capitate. Striae distinctly punctate, radiate, 5 to 7 in 1 c.d.m., not reaching to the raphe, and leaving a rather large hyaline area round the central nodule. Length, 2 to 4 c.d.m. Fresh and brackish water. — Throughout Europe. 1 88 NAVICULA. We give the description and particulars as to the dispersion of N. capitata according to the authors. We reproduce (fig. 719^) the figure which Ehrenberg gives of his form in the ': Mikrogeologie " and (fig. 7 19^) that of Schumann, which authors refer to it, although it is absolutely different. We have not in any of our collections a form referred by any serious diatomist to N. capitata Ehr. We therefore only insert the N. capitata Ehr. to record our opinion that it ought to be erased from our Catalogues, since it is impossible to know what form Ehrenberg had in view. N. dicephala W. Sm. ! (S.B.D. L, p. 53, pi. 17, f. 157 ; H.V.H. Atl., pi. 8, f. 33 and 34*, H.V.H. in Types No. 43, 343, 382, 481) 5 plate 3, fig. 138. Valve narrow, linear, with apices rostrate-capitate ; striae much shortened round the central nodule, radiate up to the apices of the valve, and about 9 to n in 1 c.d.m. Length 2*5 to 4 c.d.m. Breadth, 1 to 1*25 c.d.m. Only differs from N. Anglica Ralfs previously described by the linear form of the valve. Fresh water. — Ard. Li£g. (De Wild. ). — England, Scotland, Ireland. N. apiculata Breb. ! (Diat. Cherb., f. 5*, non W. Sm.); plate 25, fig. 720. Valve narrowly linear-lanceolate with rostrate apices. Stria; radiate, very robust 9 or 10 in i c.d.m., reaching to the raphe and almost touching the central nodule, around which they are more radiate and more distant. Girdle face narrow, constricted at the median portion and showing the striae radiate. It is this which distinguishes the N. apiculata from N. cancellata, of which, in other respects, it has all the appearance. Length, 5 to 7 c.d.m. Breadth, 1 c.d.m. Marine. — England, France. Found probably on other shores washed by the North Sea. N. Kiitzingiana H.L. Sm. ! (Spec. Typ., No. 287, A.J.Q.M., 1878. N. arenicola Grun. ! 1882 ; Foss. Diat, pi. 30, f. 76-77*) ; plate 25, fig. 721. Valve linear-elliptic, narrow, very gently inflated at the median portion ; striae radiate, about 20 in 1 c.d.m., but the median much more distant. Length of valve, 1*5 to 2 c.d.m. Breadth, 0.5 c.d.m. Marine. — France, England. NAVICULA. 189 IV. All the Stria: perpendicular to the raphe. N. directa W. Sm. ! (S.B.D., i., p. 56, pi. 18, f. 172*; sub Pinnularia ; in Type No. 394) ; plate 25, fig. 722. Valve linear-lanceolate, infinitesimally attenuate up to the acute apices. Striae about 7 in 1 c.d.m., exactly perpendicular to the raphe, which they almost touch. Length, 6 to 9 c.d.m. Marine.— England (W. Sm. !). Scotland (W. Arn. !). Ireland (O'Meara). This diatom is not common, but will certainly be found in other parts of the North Sea. var. subtilis. {Finn, subtilis Greg., Clyde, p. 488, pi. 9, f. 19*) ; plate 25> fig- 723- More rhomboidal and at the apices more acute than the type form ; 9 or 10 delicate costae in 1 c.d.m. Marine — Ccast of Scotland (Lamlash Bay, Greg. 1. N. Northumbrica Donk. (Q.J. M.S., 1861., i., n.s., p. 9., pi. 1., t. 5 ; id., Brit. Diat, p. 54, pi. 8, f. 1* ; in H.V.H.'s Types oi Syn., Nos. 13, 116, and 369) ; plate 25, fig. 726. Valves narrowly lanceolate, with apices attenuate-acute. Striae about 7 or 8 in 1 c.d.m., very delicate and perpendicular to the raphe, the median somewhat coarser and more distant. Central nodule opaque, very con- spicuous. Girdle face very broad, subquadrangular, somewhat concave from the sides of the valve. Length of valve, about 5^5 to 6-5 c.d.m. Breadth, somewhat more than 1 c.d.m. Marine. — England, Ireland, France. B. Terminal nodules distant from the apices of the valve. 1. Valve with equal sides. N. superimposita Ad. Schm. (Nordsee, p. 90, pi. 2, f. 34*), plate 25, fig. 724. Valve lanceolate or sublanceolate, with apices rounded, more or less capitate, with longitudinal median portion considerably super-elevated, in such a manner as to simulate a second smaller valve placed on the lower. Striae robust, radiant, shortened, 4 or 5 in 1 c.d.m., not reaching to the raphe, and leaving a considerable stauroform hyaline space round the central nodule. Length, 9*5 to 11*5 c.d.m. Marine. — North Sea (Hvidingsoe, A. Schm.). TQO NAVICULA. N. compressicauda Ad. Schm, (Nordsee, p. 91, pi. 2, f. 35 ; Atl., pi. 46, f. 62*), plate 25, fig. 725. Valve broadly lanceolate elongated, with apices obtuse, compressed ; striae robust, finely divided crosswise, distant, about 5 in 1 c.d.m, radiant at the median portion of the valve, perpendicular at the apices, not reaching to the raphe; those in the middle distant ; central nodule surrounded by a rounded hyaline area. Length, 11 to 12 c.d.m. Breadth, 2^25 c.d.m. Marine. — North Sea at Solsvijj (Ad. Schm.), 2. Valve with somewhat eccentric structure. N. Cesatii Rab. (Sussw. Diat, p. 39, pi. 6, f. Sg—Cy/nbel/a I H.V.H. Atl., pi. 8 f., 35 * ; in Types No. 47, 484, etc.), plate 3, fig. 143. This diatom, which is perhaps a Cymbella, has very narrowly lanceolate valves and terminal nodules, considerably distant from the apices of the valve. Fresh water. — Berg. (Delogne), England. N. inaequilatera Lag. (Diat Spitzb., 1873, p. t,3, p1- 2, f. 10*— Cymbella subaqualis W. Sin.), plate 25, fig. 727. Valve lanceolate, narrow, with somewhat unequal margins, apices rostrate- capitate. Transverse striae radiate, rather fine, 12 to 14 in 1 c.d.m.. Length of valve, 3 to 4 c.d.m. Breadth, about 75 to 1 c.d.m. Girdle face with straight margins, not inflated at the median portion. Fresh water— England (Balfour and W. Sm.). Spitzbergen (Lagerstedt). Will probably be found elsewhere. III. Didymae. A . Valves having both beads and casta:. Valves fur- nished with robust costse -J throughout its extent. Intercostal beads very small, difficult to be seen. f Median costas reaching up to the mar- gin of the valve ; two rows of beads between the costae . . . N. Crabro. Median costas not reaching up to the margin of the valve ; a single row of beads between the costas . . N. interrupta. „ Intercostal beads very coarse with smaller beads interposed N. Beyrichiana. I Valves with costae more distant at the constriction . . N. splendida. NAVICULA. I9I A A. Valves having either beads or irresolvable costa:. I. Valves with large quadrangular central nodule prolonged into horns along the raphe. a. VALVES REALLY MONILIFORM OR APPARENTLY SO IN CONSEQUENCE OF THE PRESENCE OF LONGITUDINAL COST.E. Valves distinctly monili- forni. Valves robust, with coarse beads, very visible. Striation identical over all the valve and not interrupted at the median portion. Striation interrupted at the median portion. I f Valves small, very slightly con- stricted ; sulci straight, with beads not very distinct . N. didyma. Valves very large, conspicuously constricted ; sulci dilated near the central nodule, with very distinct beads . . . N. fcomboides. Striation interrupted by a narrow- band " . N. Weissflogii. I Median portion of the valve hyaline, with some isolated beads ; beads on the margin of the valve conspicuously longer than the others . N. [_ Valves small, with delicate beads N. Bombus. vacillans. aa. VALVES NOT MONILIFORM, WITH COS'LE MORE OR LESS IRRESOLVABLE. Valves distinctly constricted at the median portion. Costa; showing fine transverse stria? in oblique light Costas not ( Striae robust, 6-8 in 1 c.d.m. crossed by Costse more or less irre- solvable into coarse beads. I longitudinal j Striae fine, approximate, 11-12 sulci. v. in 1 c.d.m. f A longitudinal sulcus in the middle of the breadth of the Costas striae .... crossed by I longitudinal \ A longitudinal sulcus following sulci. the margins of the valve [_ Three longitudinal sulci Valves linear - elliptic, f" Sulcus surrounding the raphe, very broad and ' lg the outline of the central nodule C Sulcus si not constricted or | tracinj scarcely constricted > in the middle = N. 1 contigua (A. Schm.) . Sulcus narrower, interrupted round the central CI. . . . l_ nodule . N. constricta. N. Entomon. N. incurvata. N. lineata. N. subcincta. N. Chersonensis. var. Eudoxise. var. Eugenia. II. Valves with a small central nodule, striae only present at the margin of the valve . . . . . . . n. musca. 192 NAVICULA. A . Valve furnished with robust costcc. a. Two rows of small beads between the costae. N. Crabro Ehr. (Mikr., pi. 19, f. 29.; H.V.H., pi. 9, f. 1, 2*; Type No. 101), plate 3, fig. 144. Valve sub-elliptic, constricted or not constricted at the median portion. Raphe surrounded by a narrow hyaline zone ; central nodule square, very lobust. Sulci narrow, very approximate to raphe, almost straight, slightly inflexed in the middle and at the apices. Costae convergent at the median portion, radiate at the apices, about 3.5 to 4 in 1 cd.m., and between each of which are found two rows of small beads. Length, 8 to 12 cd.m. Marine.— Ostend (Deby). Blankenberghe (H.V.H.). England (Norm., Stolt.). Scotland, Ireland (O'Me. ). Probably throughout the coasts of the North Sea. N. Crabro is excessively variable and all the forms are connected by infinitesimal transitions ; Prof. Cleve also considers, as simple varieties, the numerous forms which have been raised by authors into the rank of species. The forms which we give (fig. 144) consist of the var. Fandura (N. Pandura Breb., N. Crabro Donk.) on the right, and the var. tnultieostata (N. multicostata Grun., AT. crabro Ad. Schm.) on the left. a. a. A single row of beads visible between the costae. N. interrupta Kutz. (Bac, p. 100, pi. 29, f. 93; h.v.h. Atl., pl. 9, f. 7 and 8* ; Type No. 103) ; plate 3, fig. 145. Valve deeply constricted, with suborbicular lobes. Raphe surrounded by a rather broad hyaline zone. Sulci more distant from the raphe, almost straight. Costae not reaching to the margin of the valve at the constricted portion, about 4.5 in 1 cd.m., straight at the median portion of each lobe, convergent at the median portion of the valves, radiate at apices. A single row of beads, visible with difficulty between the costae. Length, 7 to 8 cd.m. Marine— Ostend (Deby). Antwerp (Scheldt). On all the shores of the North Sea. N. Beyrichiana Ad. Schm. (Ad. Sm. Atl., pl. 69, f. 16 and 17*); plate 25, fig. 728. Valve elliptic, with apices sub-cuneate, obtuse, constricted at the median portion. Central nodule large, quadrangular. Sulci broad, showing a row of NAVICULA. 193 small beads near the raphe. Costas very robust, scarcely radiate, 4.5 to 5 in 1 c.d.m. Intercostal intervals showing coarse beads intermixed with smaller beads. Length of valve, 10 to 14 c.d.m. Breadth, 3 to 5 c.d.m. Marine — Scheldt, between Antwerp and the sea (H.Y. H. i Very rare. This form has been again reported on our coasts, and belongs to warmer regions. Possibly it may have been brought by a ship. Pi of. Cleve refers JV. Beyrichiana to N gemmatula Grun., of which it should be only a variety. N. splendida Greg. (T.M.S., 1856, iv., p. 44, pi. 5, f. 14 ; h.v.h. Atl, pi. 9, f. 4* ; in Type No. 104), plate 26, fig. 729. Valve elongate, panduriform. Striae 11 to 12 in 1 c.d.m., formed of coarse beads, separated from the raphe by a broad sulcus, either smooth or furnished with rudimentary beads. Central nodule quadrangular, surrounded by 4 or 5 robust costae. Length, 12 to 15 c.d.m. Marine. — Scotland. Ireland, and probably elsewhere. var. Puella Ad. Schm. (Schm. Atl., pi. 12, f. 13*), plate 25, fig. 730. Valve small, narrow, only showing 2-3 rows of longitudinal costae. Length, 6 to 10 c.d.m. Breadth, 1*5 to 2-5 c.d.m. Marine. — North Sea. A A. Valve either furnished with beads or furnished with costa. N. bomboides Ad. Schm. (N.S. Diat, p. 85, pi. 1, f. 2 ; h.v.h. Atl. Supp., f. 19* ; in Type No. 74, etc.), plate 3, fig. 146. Valve elliptic, gently constricted at the median portion. Raphe surrounded by a narrow hyaline area. Sulci broad, abruptly dilated at the median portion. Striae straight at the constricted portion, then becoming gradually more and more radiate. 4 or 5 in 1 c.d.m., formed of very large beads, subquadrangular, and almost touching one another, in such a way that the entire surface of the valve somewhat resembles the paving of a street. Length, about n c.d.m. Marine. — Potter's clay at Ostend (Deby) ; Blankenberghe (H.V.H.) ; Shores of the North Sea. N. didyma Ehr. (Kutz. Baa, p. 100, pi. 4, f. 7: H.V.H. Atl., pi. 9, f. 5 and 6; Suppl. f. 20 at another focus*; Type No. 102), plate 3, fig. 147. Small, median constriction scarcely pronounced ; sulci straight. Striae approximate, about 8 in t c.d.m. Length, about 5-5 c.d.m. Marine. — Antwerp (Scheldt), Ostend, Blankenberghe; England (Stolt. , Kitton, Comber, W. Sm.; Norm.). Rather common throughout Europe. O 194 NAVICULA. N. Weissflogii A. Schm. (Uber N. Weissflogii and N. Grundkri in Giebel's Zeitschr, 1873; H.V.H. Atl. Suppl., f. 21), plate 3, fig. 148. This beautiful species, very similar to N. didyma, differs from it essentially by its strange constriction, by the band not being moniliform in the middle of the valve and by the arrangement of the beads near this band, and of which the entirety forms a St. Andrew's Cross. Stride about 7 in 1 c.d.m. Length about 4-5 to 5 c.d.m. Marine. — Blankenberghe ; rather rare. N. Bombus Ehr. (Abh., 1844; H.V.H. Atl. Suppl. , f. 22*; in Type No. 104), plate 3, fig. 149. Rather large ; valve deeply constricted with subcordate lobes ; raphe surrounded by a broad hyaline zone, with sulci showing small beads in irregu- larly curved rows. Striae 6 in 1 c.d.m. with coarse beads; those on the margin of the valve elongate and much larger than the others. Median portion of the valve hyaline, showing only some large isolated beads. Length, about 8 c.d.m. Marine. — Blankenberghe (rare). Found in France, England, Scotland, Ireland and Norway. N. vacillans Ad. Schm. (Atl., pi. 8, f. 61 ; H.V.H. Atl, plate 9, f. 9*), plate 3, fig. 150. Very small, valve narrowly elliptic, gently attenuate at the median portion. Central nodule large, raphe surrounded by a narrow hyaline zone. Sulci approximate to raphe, almost straight, feebly flexed towards the exterior round the central nodule. Striae finely punctate transversely, feebly radiate, about 16 in i c.d.m. Girdle face constricted in the middle. Length, about 2 c.d.m. Marine. ^Ostend (H.V.H.) ; very rare. The above form constitutes A^ vadllans forma minuta. The true type is from 4 to 6 c.d.m. in length. N. constricta Grun. (Verh., i860, p. 535, pi. 3, f. 18; in h.v.h. types No. 103 ; N. musca Donk.; N. Donkinii Ad. Schm. Atl., pi. 12, f. 63*), plate 26, fig. 731. NAVICULA. 195 Valve "sub-elliptical, feebly constricted at the median portion ; with sub- cuneate apices. Central nodule large, quadrangular. Striae, 7 or 8 in 1 c.d.m., resolvable into beads, feebly radiant. Length, 6 to 15 c.d.m. Breadth at the median portion, 2 to 2*5 c.d.m. Marine. — North Sea (England ! Norway.) N. Entomon (Ehr.) Ad. Schm. (Nordsee, pi. 1, f. 13*), plate 26, fig. 732. Valve elongated, moderately constricted at the median portion, with tongue-shaped segments. Striae indistinctly resolvable, 6 to 8 in 1 c.d.m., feebly convergent at the median portion of the valve, radiant at the apices, occupying only three-fifths of the valve. Sulci very broad, showing a row of scattered beads. Nodule quadrangular, very large. Length, 7 to 15 c.d.m. Breadth of segments, 3 to 4 c.d.m. Marine. — North Sea, etc. N. incurvata Greg. (T.M.S., 1856, iv., p. 44, pi. 5, f. 14; Ad. Schm. Nordsee, pi. 2, f. 6*), plate 26, fig. 733. Resembles the preceding species, but is much narrower, more elongated, with finer and more approximate striae, about 11-12 in 1 c.d.m. Marine. — North Sea. May this not be a form of the preceding ? N. lineata Donk. (Brit. Diat, p. 8, pi. 1, f. 8 ; Ad. Schm. Nordsee, pi. 1, f. 17*), plate 26, fig. 736. Valve linear-elliptic, somewhat constricted at the median portion, with rounded apices. Striae irresolvable, feebly radiant, 9 to 10 in 1 c.d.m., crossed in the middle of their length by a smooth longitudinal line, parallel to the margins of the valve. Raphe surrounded by a broad hyaline area showing one or two rows of feebly visible puncta. Central nodule large, subquadrangular. Length, 4 to 8 c.d.m. Breadth, 2 to 3 c.d.m. Marine. — North Sea (England! Scandinavia — Cleve). N. subcincta Ad. Schm. (Atl., pi. 13, f. 41*), plate 26, fig. 737- Valve feebly constricted at the median portion, with apices rounded, some- times sub-cuneate ; striae somewhat radiant, considerably distant from the 196 NAVICULA. raphe; 6 or 7 striae in 1 c.d.m., indistinctly resolvable and crossed by a long smooth sulcus, approximate to the margin of the valve, the outline of which it follows. Central nodule large, quadrangular. Length, 6 to 9 c.d.m. Breadth, 2-25 to 2-5 c.d.m. Marine. — North Sea. N. Chersonensis Grun. (Ad. Schm. Atl., pi. 12, f. 40*), plate 26, fig. 738. Valve parduritorm, with sub-cuneate segments. Striae 8 to 13 in 1 c.d.m., more or less resolvable, continuing in the sulci and approximate to the raphe, feebly radiant, the median straight, more compact than the others. Striae crossed by 2 to 5 longitudinal lines, more or less arcuate. Central nodule large, quadrangular. Length, 5-5 by 15 c.d.m. Breadth of segments, 1 to 3 c.d.m. Marine. — North Sea, &c. N. musca Greg. (Diat. of Clyde, p. 7, pi. 1, f. 6*; Ad. Schm. Nordsee, pi. 1, f. 15*), plate 26, figs. 734 and 735. Valve conspicuously constricted with subtriangular lobes, apices cuneate. Striae leebly radianc, 7 in 1 c.d.m., occupying only a moiety of the valve, and formed usually of 4 or 5 small beads arranged in two rows, separated by a longitudinal sulcus. Central nodules small, elongated. Raphe surrounded by a very broad hyaline area, dotted here and there with the rudiments of beads. Length, 5 to 6 c.d.m. Breadth, about 2 c.d.m. at the constriction. Marine. — Scotland, Ireland, Norway. N. Eudoxia A. Schmidt. (Atl, pi. 8, f. 39 and 40*), plate 26, fig- 739- Valve elliptic, linear, scarcely if at all constricted at the median portion, apices obtuse, rounded. Central nodule large, quadrangular, raphe surrounded by a broad sulcus, showing rudimentary costae or a line of beads. Costa? robust, slightly radiate, 6 in 1 c.d.m. Length, 7 to 9 c.d.m. Breadth, 2-5 c.d.m. Marine.— Maritime Scheldt, rare (H.V.H.). Ireland (O'M.), Solsvig (Ad. Schm). N. Eugenia Ad. Schm. (Atl., pi. 8, f. 44*), P^te 26, fig. 740. Closely allied to the preceding, from which it differs by its size, often very- small, by the sulcus surrounding the raphe, which is quite smooth, and by a NAVICULA. 197 longitudinal sulcus, which on either side of the valve interrupts the costoe, towards the moiety of the length. Costae robust, about 5 or 6 in 1 c.d.m. Breadth, 6 to 9 c.d.m. Marine. — Rare : Maritime Scheldt ; Blankenberghe. Prof. Cleve considers the two preceding forms as simply varieties of A7. coniigua Ad. Schm., a type form which has not yet been found on our coasts. Valves furnished with costae. IV. Ellipticae. Valves showing small beads between the costse. f T , f .Sulcus approximate to I wo rows of u w o^it-v,;; ,, , , raphe . . . N. Srnitnii. small beads ' between the 1 costas. No beads between the costae. Valves oval , rounded. Sulcus dividing the costas into two equal parts . N. I A single row of beads between the costse . N. f Costae straight, continued . . . N. I -j Costae more or less interrupted, sometimes forming thick elongated b:>ads, some- (_ times simply attenuate here and there . N. Valve moniliform, not furnished - with costae. l^Valves strictly elliptic f Nodule very elongate . N. . N. Nodule quadrangular or rounded. f Sulci abruptly flexed from above round the central nodule . . . . N. > 1 I Sulci straight or flexed from below near the (, central nodule ; valve broadly elliptic . N. nitescens fusca. suboibicularis. notabilis. advena. littoralis. elliptica. oculata. Valve appearing hyaline, with dry objectives. Striation very delicate, monili- form, only becoming visible by means of homogenous objectives of wide (_ aperture . . . . . . . , . . N. hya'ina. A. Valve furnished with coster. N. Smithii Breb. (in w. Sm. S.B.D., ii., p. 92 ; H.V.H. Ad., pi. 9, f. 12; Supp., f. 23*; Type No. 104), plate 4, fig. 151^,/;. Valve oblong or linear-elliptic, sometimes somewhat constricted in the middle, with apices broadly rounded, somewhat subcuneate. Central nodule large, quadrangular ; terminal nodules not reaching to the apex of the valve ; raphe surrounded by a rather broad hyaline zone. Sulci enlarged in the middle of the valve, diminishing infinitesimally cuneate near the apices. Costse feeble, 5 in 1 c.d.m., separated by two rows of small beads. Length, about 9 to 10 c.d.m. Marine. — Antwerp (Scheldt), Blankenberghe. Througnout the North Sea coasts. This Navicula assumes very different forms. That described above is the one most frequently found at Blankenberghe and Antwerp, where it is rare. 198 NAVICULA. Much more frequently found is an elliptic form represented in H.V.H.'s Atl. Supp., f. 23 (plate 4, fig. 151/'), and which constitutes the D. Major of Prof. Cleve. The most essential character of N. Smithii is the double row of beads found between the costae. var. aestiva. {N. (estiva Donk. in H.V.H 's Type of Syn., No. 104). Differs from the type form with which it is generally accompanied by its more regularly elliptic form and its finer striation. Marine. — Coasts of England. var. scutellum. (TV. scutellum O'Meara, in H.V.H.'s Atl., pi. 9, f. 11), plate 4, fig. 152. Very small ; valve suborbicular elliptic ; striae about 8 in 1 c.d.m., perpendicular to the raphe at the median portion, then becoming more and more radiate. Length, about 3 c.d.m. Breadth, 2-5 c.d.m. Marine. — Blankenberghe (H.V.H. , very rare). Ireland (O'M.). Observ. — When I drew the figure in the Atlas I did not possess the excellent homogenous objectives which have since been invented, and I was consequently unable to recognize the true nature of the striation. Since then I have found that there exists two rows of excessively delicate beads between the striae, and consequently I refer this form, which appears to be the N. scutellum of O'Meara, to N. Smithii. N. nitescens Greg. (Diat. of Clyde, p. 15, pi. i, f. 16*), plate 26, fig. 747. Valve elliptic-lanceolate, with apices subobtuse. Transverse striae, 8 in i c.d.m, cut by the sulcus almost in the middle of their length. Inter- costal spaces showing two rows of small beads well marked in the portion of the valve exterior to the sulcus ; rudimentary and little visible in the internal portion. Length, 5 to 8*5 c.d.m. Breadth, 2 to 3.5 c.d.m. Marine— and also found in the stomachs of marine animals. Coasts of England, Scotland, Norway, etc. N. fusca Greg. (N. Smithii var. fusca Greg. Diat. of Clyde, p. 14, pi. 1, f. 15; H.V.H. Atl. Supp., f. 24*: Type No. 105), plate 4, fig- 153- This diatom is distinguished from N. Smithii by its generally somewhat smaller size, and because it has only a single row of rather large beads between the costae. Marine. — Blankenberghe (rare)— England, Scotland, Denmark. NAVICULA. 199 Prof. Cleve distinguishes the following forms in N.fusca from the North Sea : — var. norvegica CI. (A fusca Ad. Schm. Ad., pi. 7, f. 2-3*), plate 26, fig. 741. Valve broadly elliptic ; ro costal and ic longitudinal puncta in 1 c.d.m. var. subrectangularis CI. (A jusca Ad. Schm. Atl., pi. 7, f. 4*), plate 26, fig. 742. Very large, subrectangular; 8-5 to 13 c.d.m. in length ; S costse and S longitudinal puncta in 1 c.d.m. var. Gregoni CI. (A. Smithii, var. fusca Greg.), Diat. of Clyde, pi. 9, f. 15*), plate 26, fig. 743. Elliptic, subrectangular. Length, 17 c.d.m.; 7 costal and 7 longi- tudinal puncta in 1 c.d.m. var. delicatula Ad. Schm. (Atl., pi. 7, f. 7-8*), plate 26, fig. 744. Elliptic. Length, 7 to 13 c.d.m. ; 7 to 10 longitudinal costae and 10 to 15 longitudinal puncta in 1 c.d.m. var. tenuipunctata CI. (A fusca, H.V. H. in Syn. Suppl., f. 24*), plate 4, fig. 153. 6 to 9 costae and 12 to 18 longitudinal puncta in 1 c.d.m. var. hyperborea. (A. hyperborea Grun., Verb., 1S60, p. 531.pl. 1, f. 16*), plate 26, fig. 745. Sulci abruptly curved round the central nodule ; 7 costae in 1 c d.m. Marine. — Bohuslan (Sweden, Grun.) Blankenberghe, H.V. H. forma excisa. (A. excisa Ad. Schm., Nordsee, pi. 2, f. 9*), plate 26, fig. 746. Valve gently constricted at the median portion ; 9 costae in 1 c.d.m. Marine. — North Sea. N. suborbicularis Greg, (i)iat. of Clyde, p, 15, pi. 1, f. 17*; in H.V.H.'s Types, No. 197), plate 26, fig. 748. Valve small, broadly oval-suborbicular. Costae robust. 6 in 1 c.d.m. ; ■ terminated by a large bead, not showing small beads in the intercostal spaces, the Central nodule large, quadrangular, elongated. Sulci very attenuate near central nodule, which they touch. Length, 4 to 5 "5 c.d.m. Breadth. 2 "5 to 3'5 cd-m- Marine. — Blankenberghe (H.V.H.). England, various localities. Norway. var. coffeaeformis Ad. Schm. (Schm. Atl., pi. 8, f. 6*), plate 26, fig. 749. Smaller and much more delicate in all its parts. Striae, 8 to 12 in 1 c.d.m., feeble, delicate. Horns of nodule scarcely arcuate. Passes into the type by every gradation. Marine. — North Sea. 20D NAVICULA. N. notabilis Grev. (T.M.S., 1863, iii., p. 18, pi. 1, f. 9; Sch. Atl., pi. 8, f. 46-47*), Piate 26, fig. 750. Valve oval-elliptic, with sulci scarcely attenuate near the median portion. Costae robust, 10 in 1 c.d.m., not showing small beads in the intercostal spaces, interrupted by two broad and deep depressions, one at the middle of their length, the other between their apices and the sulcus. Marginal costae in addition interrupted by one or two narrow sulci in a manner to simulate beads. Length, 3 c.d.m. Breadth, abjut 2 c.d.m. Marine. — Not yet found in Europe. var. expleta Ad. Schm. (Nordsee, p. 88, pi. 2, f. n ; Atl., pi. 8, f. 48-5°*), Plate 26' fig- 751- The median depression of the cos! a; disappears, and these are trans- formed into a series of false puncta forming longitudinal lines in zig-zag. Marine —Maritime Scheldt (H.V.H.). Hvidingsoe (Ad. Schm.). English Channel. Estuary of Shannon, Ireland The form found in the Scheldt is less oval and more subquadrangular than the type form figured by Dr. A. Schmidt. N. advena Ad. Schm. (Atl., pi. s, f. 29* ; H.v.H.'s Types No. 197), plate 26, fig. 752. Valve longly linear-elliptic, sometimes somewhat constricted at the median- portion. Costre 9 in 1 c.d.m., delicate, parallel, continuing into the sulci. Central nodule of medium size, with straight horns, approximate. North Sea. — Scotland (Cumbrae !) var. parca. (Ad. Schm. Atl., pi. 8, f. 20. 21, 22*), plate 26, fig. 753. Smaller and more delicate ; valve longly elliptic. Marine. — North Sea. A A. Valve moniliform, not furnished with costcc. N. littoralis Donk. (Brit. D., p. 5, pi. 1, f. 2; H.V.H. Atl. Supp., f. 25* in Type No. 104), plate 4, fig. 154. Valve oval. Nodule very elongate. Raphe not surrounded by a hyaline area. Sulci completely straight, and quite approximate to the raphe. Striae 14 in 1 c.d.m., perpendicular to the raphe at the median portion, becoming more and more radiate near the apices. Length, about 4 to 5 c.d.m. Marine. — Blankenberghe (very rare), England. NAVICULA. !OI N. OCulata Breb ! (in Desm. ed., 1854, No. no; H.V.H. At!., pi. 9, f. 10*), plate 4, fig. 155. Valve linear-oblong, with broadly rounded apices. Central nodule sub- quadrangular ; raphe surrounded by a narrow hyaline zone ; sulci approximate to raphe, straight, gently incurved near the central nodule; striae finely punc- tate, straight at the median portion, then becoming little by little radiate, 17 in 1 c.d.m. Length, 2 to 2-5 c.d.m. Breadth, about 75 c.d.m. Fresh water. — Brussels (Botanical Gardens, Delogne), France. N. elliptica Kutz. (Baa, p. 98, pi. 30, f. 55; h.v.h. Atl., pi. 10, f. 10*; Type No. 107), plate 4, fig. 156 (first figure). Valve oval-elliptic or oblong-elliptic. Raphe robust, surrounded by a rather broad hyaline area, abruptly enlarged round the central nodule; sulci very approximate to the raphe, following the outline of the hyaline zone ; striae formed of coarse puncta, straight at the middle of the valve, and becoming little by little radiate near the apices, 1 1 in 1 c.d.m. Length, 25 to 3*5 c.d.m. Breadth, 1*3 to 1*5 c.d.m. Fresh and brackish water. — Rather common throughout Europe. var. ovalis Hilse, plate 4, fig. 156 (second figure). Valve elliptic ; central nodule very large, rounded ; striae fine, 13 to 19 in 1 c.d.m., formed of puncta arranged in irregular longitudinal rows. Length, 3-5 to 4 c.d.m. Breadth, 2 to 2-5 c.d.m. var. oblongella Naeg. (H.V.H. Atl., pi. 10, f. 12*, in Type No. 108), plate 4, fig. 157. Small, very elongate, about 16 striae in 1 c.d.m. Length, 2 c.d.m. Breadth, -75 c.d.m. var. minima (H.V.H. Atl., pi. 10, f. ir ; Nav. Puellx CL), plate 4, fig. 158. Very small, being little more than 1 c.d.m. in length. N. hyalina Donk. (Q.J.M.S., iS6r, p. 10, pi. i, f. 6; Brit. Diat., p. 5, pi. i, f. i ; Ad. Sch. Atl., pi. 70, f. 1-4*), plate 26, fig. 754. Valve linear elliptic, with obtuse apices. Raphe placed in a deep sulcus, abruptly attenuate near the central and terminal nodules. Striae excessively delicate, 20 in 1 c.d.m., appearing marginal in axial illumination, and irregu- larly bordered near the internal margin with coarse dots ; between these dots and the median sulcus the valve is depressed, and in this depression the striae 202 NAVICULA. are less marked, and are only apparent with oblique illumination. Length, up to 6 c.d.m. Breadth, 2*5 c.d.m. Valve excessively delicate, apparently hyaline under the best dry objectives. Marine. — Very rare? On the sands at the coast at Cresswell and Boulmar (England ; Donkin). Curabrae (Scotland, Coll. W. Arnott in Coll., H.V.H.). V. Lyratae. f Sulci more or less divergent, equally broad through- out . . . . . N. Lyra. Sulci straight or somewhat convergent, much broader at their median portion than at the apices . N. spectabilis. Blank space surrounding the raphe, with median apices clavate . . . . , N. forcipata. 0, , f Central nodule surrounded by a nar- Blank space , . r , • . J ,- Valve with coarse puncta. Valve with fine puncta; sulci ■ K- row.hyahne area ; sulci not reaching J surrounding ■' J a nver- \ gent. strongly conver- ~\ jV rounoing to the apex of the valve . . N. abr^pta. j with median apices not clavate. Central nodule surrounded by a broad hyaline area ; sulci reaching almost to the apices . . N. pygmaea. A. Siricz formed of coarse granules. N. Lyra Ehr. (KUtz. Baa, p. 94, pi. 28, f. 55; h.v.h. Atl., pi. 10, f. 1 and 2*; Type No. no), plate 4, fig. 161. Valve broadly elliptic, with apices often somewhat diminuate subrostrate. Raphe surrounded by a narrow hyaline zone, dilated into a stauros round the central nodule. Striae formed of coarse puncta, about 7 to 9 in 1 c.d.m., more and more radiate from the median portion, and interrupted on each side of the raphe by a sulcus, the bottom of which is generally smooth, but where the striae continue sometimes more feebly, incurved at the middle where it rejoins the stauroneiform hyaline space, in such a manner that the entire smooth spaces have the appearance of a lyre. Length, 11 to 12 c.d.m. Breadth, about 5 c.d.m. Marine. — Blankenberghe (rare). Found on all the North Sea coasts. N. spectabilis Greg. (Diat. of Clyde, p. 9, pi. 1, f. 10*), plate 27, fig- 757- Probably only a form of the preceding, from which it differs essentially in that the sulci are at least twice as broad, and are finely dotted. Marine. — Not yet found in Belgium. Scotland, Ireland, France, Sdlsvig, Cuxhaven, Marstrand. NAVICULA. 203 A A . Valves with finely punctate stria:. N. abrupta Greg. (IV. Lyra vat. abrupta Gre<>. Diat. of Clyde, p. 14, pi. 1, f. 14; H.V.H. Atl., pi. 10, f. 4*; in Type No. 104), plate 4, fig. 162. Differs from the preceding by the valves being regularly oval, with apices never diminuate, and by the sulci always recurved on the side of the raphe, and abruptly terminated at a certain distance from the apices. Striae about 10 in 1 c.d.m. in my specimen, which appears to be smaller than usual. The valve appears colourless when dry. Marine. — Very rare. — Washing of mussels (Debj. ). England, Scotland, Bahnsie. N forcipata Grev. (Q.J. M.S., 1859, vii., p. 83, pi. 6, f. 10 and 11 ; H.V.H. Atl, pi. 10, f. 3 ; in Type No. 104), plate 4, fig. 163. Differs from N. Lyra by its smaller size, its striae approximate and finely granulate, and especially by the clavate enlargement (which is characteristic) of the median apices of the raphe. Striae fine, about 15 in 1 c.d.m. Valve brown when dry. Marine. — Rather common. Scheldt at Antwerp, Blankenberghe. England, Scotland, France. N. pygmaea Klltz. (Spec. Alg., p. 77; N. minutula IV. Sm. ; H.V.H. Atl., pi. 10, f. 7*, in Types No. 9, 11, 77, 95, 99, 192, etc.), plate 4, fig. 164. Small, valve narrowly elliptic. Raphe surrounded by a hyaline zone, narrow, very much enlarged quite round the central nodule. Striae very fine, about 26 in 1 c.d.m., becoming gradually radiate from the middle of the valve, interrupted on each side of the raphe by a sulcus strongly incurved at the median portion, and of which the apices rejoin the raphe somewhat before reaching the apex of the valve. Length, 2^25 to 4'5 c.d.m. Breadth, 1 to 1*25 c.d.m. Brackish water.— Antwerp, Blankenberghe; England (Kitton), France. Fresh water. — Louvain (P.G. ). VI. Hennedyeae. f Margins of valve with coarse beads ; sulci with coarse scattered beads . N. prsetexta. I J Margins of valve with coarse beads; sulci finely dotted, showing in the middle an arc formed by ro»vs of 1; to 6 coarse beads . . . N. Sandriana. i I. Margins of valve with fine beads ; sulci smooth or finely dotted . . N. Hennedyi. 204 NAVICULA. N. praetexta Ehr. (Acad.. Berlin, 1840, p. 20; H.V.H. Atl., pi. 9, f. 13*), Plate 4, fig. 159. Valve broadly elliptic. Raphe surrounded by a very narrow hyaline zone, enlarged in the form of a stauros near the central nodule. Normal striation in the form of two bands, one at the margin of the valve, the other running the length of the raphe formed of coarse granules with an intermediate space occupied by a broad depression, the bottom of which is irregularly granulated ; normal striae, straight in the middle of the valve, then gradually radiate 6 or 7 in 1 c.d.m. Girdle face quadrangular, oblong, deeply constricted at the central nodule, girdle face showing six longitudinal lines of fine granules, of which the four interior are arranged in pairs. Length, 7 to 9 c.d.m. Breadth, 5*5 c.d.m. Marine. — Blankenberghe, Scheldt at Antwerp (rare). Scotland, England, Ireland (O'Me.). France, Denmark, Holland. N. Hennedyi W. Sm. (S.B.D., ii., p. 93; H.V.H. Atl., pi. 9, f. 14 ; Type No. 109), plate 4, fig. 160. Valve oval ; raphe surrounded by a very narrow hyaline zone, enlarged into a stauros near the central nodule; stria; finely granular 10 in 1 c.d.m., gradually radiate from the middle of the valve, interrupted on each side by a crescent-shaped depression, the bottom of which is smooth or very finely dotted. Length, about 6 to 7 c.d.m. Breadth, about 4 c.d.m. Marine.- -Very rare. Blankenberghe. England, Scotland, Ireland, and on all the North Sea coasts. var. clavata (A', clavata Greg., T.M.S., 1856, iv., p. 46, H.V.H. Atl., pi. 5, f. 17). Differs from the type form by the apices gently subrostrate, and by the depression, which is very narrow. Marine. — Blankenberghe ; very rare. England, Scotland, Ireland. var. nebulosa (N. mbulosa Greg., Diat. of Clyde, p. 68, pi. 1, f. 8 ; Ad. Schni. Atl., pi. 3, f. 14*), plate 27, fig. 755. Differs from the type form by less obtuse apices, finer striae (12-14 in 1 c.d.m.), which only occupy a narrow marginal band right round the valve. Length, 6 to 9 c.d.m. Marine. — Not yet found in Belgium, where however it will be. Scotland (Greg.), Ire- land (O'M.), Solsvig (A. Schm.), Marstrand (H.V.H. ). N. Sandriana Grun. (in Wien. Verh., 1863, p. 153, pi. 13, f. 5*), plate 27, fig. 756. NAVICULA. 205 Differs essentially from N. Hennedyi in the fact that the sulci are finely dotted, and presenting in the middle a longitudinal arc formed by rows of 5 or 6 coarse beads. The valve is also larger and more broadly rounded than in N. Henmdyi\ the striae are marginal, and those near the raphe more distant (10 in 1 c.d.m.), and formed of coarser beads. Length, about 10 c.d.m. Breadth, 6 c.d.m. Marine. — Scheldt and Blankenberghe (H.V.H.) ; Bahusee (Lagerst. ); St. Brieuc (France) and Solsvig (A. Schm); Ireland (O'M.). — This diatom, one of the most beautiful forms of the North Sea, is not excessively rare. VII. Asperae. f Hyaline space forming a band with cuneate apices, girdle face with almost straight margins ; angles verv rounded . . . . N. aspera. i ~\ I H\ aline space rounded, not cuneate; girdle face with concave margins, [ angles not rounded . . . . . N. Clepsydra. N. aspera Ehr. {Stauroptera aspera Ehr., Amer., p. 134, pi. 1, I., f. T2, etc. ; Stauroneis pulchella IV. Sm. ; H.V.H. Atl., pi. 10, f. 13, and Supp., f. 27* ; in Type No. 101, etc.), plate 4, fig. 165. Valve linear-lanceolate or elliptic-lanceolate, with apices obtuse or subacute. Raphe surrounded by a narrow hyaline zone, dilated into a hyaline cuneate band, not reaching the margins of the valve, round the central nodule, which is round, very large, but visible with difficulty. Valve apparently covered with coarse puncta, but which with the best objectives are found to be very fine striae, interrupted in their length, finely divided transversely, regularly radiate up to the apex of the valve, 9 to 10 in 1 c.d.m. Girdle face broad, elongate, with apices truncate, rounded and in the median portion constricted. Length, 10 to 18 c.d.m. Breadth, about 2-5 c.d.m. Marine. — Antwerp (very rare), Blankenberghe, Ostend. England, Scotland, find probably on all the North Sea Coasts. N. Clepsydra Donk. (Q.J.M.S., 1861, i., n.s., p. 8, pi. 1, f. 3*), plate 27, fig. 759. Differs from the preceding species by finer striae, 10 to 12 in i c.d.m., by the circular hyaline space which surrounds the central nodule, and by the girdle face being much more deeply constricted at the median portion. Marine. — Sand of seashore. England, Scotland ; France. 206 NAVICULA. My group, Aspera, corresponds with the genus Trachyncis of Prof. Cleve, a genus which appears to me to be well founded, but I have not provisionally admitted it here, in order not to interfere too much with the order adopted in the Synopsis. VIII. Stauroneideae. f Apices capitate ; puncta interrupted Hyaline space here and there . . N. Tuscula. narrow, -\ appearance j striae radiate. | Apices not capitate ; stauroneiform caused by a | ^ space showing an isolated bead . N. mutica. Stauroneiform appearance caused by a hyaline space | Hyaline space excessively broad ; valve linear-elliptic ; t striae perpendicular to the raphe . . \*N. Pinnularia. Stauroneiform c Valve lanceolate, neither rostrate nor undulate . N. crucicula. appearance, caused by more -J Valve tri-undulate, with apices apiculate-rostrate . N. integra. distant median I. striae. i. Valve linear-subelliptic . . . . N. subinflata. A . Stauroneiform appearance caused by a hyaline space. a. Hyaline space narrow, valve with radiate striae. * PUNCTA FORMING IRREGULAR LONGITUDINAL LINES. N. TllSCllla Ehr. (Stauroneis punctata Ruiz., Bac, p. 106, pi. 21, f. 9. ; H.V.H. Atl., pi. 10, f. 14; Type No. in), plate 4, fig. 166. Valves elliptic, with apices strongly rostrate capitate. Raphe surrounded by a narrow hyaline zone, dilated round the central nodule into a pseudo- stauros irregularly subdivided. Striae 7 or 8 in 1 c.d.m., becoming radiate from the middle of the valve, finely divided transversely and with frequent interruptions, the entirety forming irregular longitudinal lines. Length, about 8 c.d.m. Breadth, 2*5 c.d.m. Fresh and brackish water. — Antwerp (H.V.H.) Orval (Del.) England (Wm, Sm. and W. Arnott), and probably elsewhere. ** PUNCTA NOT FORMING LONGITUDINAL LINES. N. mutica Kutz. ! (Stauroneis Cohnii Hilse \ H.V.H. Atl., pi. 10, f. 17*; Type No. 113), plate 4, fig. 167. Valve elliptic or elliptic-lanceolate. Raphe surrounded by a narrow hyaline zone, which, round the central nodule, is dilated into a pseudo- stauros, on one of the sides of which a coarse isolated bead is seen. Striae radiate with well marked puncta, 15 to 18 in 1 c.d.m. Length, 1 to 2 c.d.m. Breadth, about 7 c.d.m. Brackish water. — Piles in the Scheldt at Antwerp. Ostend, etc. England (Kitton, Norman). Ireland (O'M.) and probably throughout Europe. NAVICULA. 207 var. Goeppertiana. (H.V.H. Atl., pi. 10, f. iS, Type No. 114), plate 4, fig. 168. Valve regularly lanceolate. Laeken, near Brussels (Del.). var. undulata. (H.V.H. Atl, pi. 10, f 2 or., in Type No. 148), plate 4, fig. 169. Margins feebly undulate. Not yet found in Belgium. var. quinquenodis (H.V.H. Atl., pi. 10, f. 21, in Type No. 146), plate 4, fig. 170. Valve showing three strong inflations on each side. Groenendael (Del.). var. ventricosa. (H.V.H.. pi. 4, f. i/>., Stauroneis venlricow Kit/z.), plate 4, fig. 171. Valve with apices rostrate-capitate. Not yet found in Belgium. a a. Hyaline space very broad, valve with striae perpendicular to the raphe. N. Pinnularia Cleve. (Sv. och Norsk D., 1868, p. 224, pi. 4, f. 1-2* ; N. quadratarea Ad. Schm.), plate 27, fig. 758. — See under (I) Pinnularia;, page 167. A A . Stanronciform appearance caused by the median stride being distant from one another. N. crucicula (W. Sm.). {Stauroneis W. Sm., S.B.D., i., p. 60, pi. 19, f. 192 ; H.V.H., pi. 10, f. 15*; Type No. 112), plate 4, fig. 172. Valve broadly lanceolate or lanceolate-elliptic, with apices obtuse, some- what constricted ; striae almost touching the raphe, slightly shortened near the central nodule. Median striae straight, more robust and more distant, and producing, under insufficient magnification, the appearance of a stauros ; the others about 16 or 17 in 1 c.d.m., fine; compact, delicately punctate, more and more radiate as they are distant from the median. Length, about 4*5 c.d.m. Breadth, 1*5 c.d.m. Brackish water.— Antwerp (Scheldt), Blankenberghe. England, Ireland, Denmark. van protracta Grun. (Arct. D., p. 35, pi. 2, f. 38; H.V.H. Atl. Supp., f. 27*; in Type No. 99), plate 4, fig. 173. Valve linear lanceolate, with apices broadly rostrate. Striae 18 to 21 in 1 c.d.m. Length, 2^25 to 3*5 c.d.m. Brackish water.— Austruweel near Antwerp(H.V.H.). Ard. Liege. (DeWild.). Cheshire, England, 208 NAVICULA. N. integra W. Sm. (S.B.D., ii., p. 96 ; H.V.H. Atl., pi. n, f. 22* ; in Type No. 55), plate 4, fig. 174. Valve lanceolate elliptic, margins with 3-7 undulations, apices abruptly rostrate-apiculate. Raphe surrounded by a narrow hyaline zone ; median stria? straight, distant, producing a pseudo-stauros under low magnification, then radiate, 23 in 1 c.d.m. Length, about 3 c.d.m. Breadth, about 1 c.d.m. Slightly brackish water. — Antwerp, Blankenberghe. England, Scotland, Ireland, Holstein. This may possibly be, according to Grunow (Arc. Diat., p. 36), only a simple variety of N. crucicula, which is a protean form analogous to JV. mutica. N subinflata Grun. (in Cleve Vega, p. 470, pi. 37, f. 50*), plate 27, fig. 760. Valve linear, more or less elliptic, somewhat inflated at the median portion with obtuse, rounded apices. Stria? almost perpendicular to raphe, 19 in 1 c.d.m. ; the twc or three central ones somewhat shortened and very distant. Girdle face rectangular with connecting zone showing fine longitudinal lines. Length of valve, 2*5 to 4 c.d.m. Breadth, 8 mill. d.m. Marine. — Norway, Grip ; Cape Wankerema. var. elliptica. -Valve more elliptic (Adriatic, Cleve and Moll Diat. No. 210). IX. Palpebrales. Valve with hyaline zone very elongate, lanceolate ..... N. palpebralis. N. palpebralis Breb. (in w. Sm., S.B.D., i., p. 50, Supp. pi. 31, f. 273 ; H.V.H. Atl., pi. 11, f. 9* ; Type No. 116), plate 4, fig. 175. Valve broadly elliptic-lanceolate, with apices acute, slightly mucronate ; stria? radiate, rather robust, not punctate, marginal, leaving round the raphe a broad hyaline space, lanceolate in form. Stria? vigorous, about 10 in 1 c.d.m. Breadth, 4*5 to 5 c.d.m. Length, 7*5 c.d.m. Marine. — Ostend, Blankenberghe (H.V.H.). Mouth of the Scheldt (Thomson). On all the North Sea Coasts. var. obtusa (H.V.H. Atl., pi. n, f. 8*), plate 4, fig. 176. Apices somewhat constricted, very obtuse. Marine. — Blankenberghe, NAVICULA. 209 var. angulosa. (A7, angulosa Greg., H.V.H. Atl., pi. 11, f. 10*; in Type No. 116), plate 4, fig. 177. Hyaline area very small, angular. Marine. — Scheldt at Antwerp ; Blankenberghe. England (Donkin), Scotland (Gregory), Ireland (O'M.). var. minor Grun. (H.V.H. Atl., pi. 11, f. n*), plate 4, fig. 178. Much smaller than the type form, scarcely 2-5 c.d.m. in length, 10 or 1 1 striae in 1 c.d.m. Marine. — Ostend. var. Barklayana Greg.? (N. Barklayana Greg.'! H.V.H. Atl., pi. 11, f. 12*), plate 4, fig. 179. Valve with margins almost straight, abruptly attenuate. Marine. — Blankenberghe. var. semiplena. (Pinnularia semiphna Grev.). Valve linear-elliptic, narrow, very elongate. Marginal striae vigorous, 10 in 1 c.d.m. Length, about 8 c.d.m. Breadth, about 2 c.d.m. Marine. — Blankenberghe (H.V.H.). Coasts of Scotland (Gregory), and probably else where. Observ. — The striae of N. pulpebralis in my plates have erroneously been drawn punctate, and so described in my Synopsis. In 1882 I fell into the same error as my predecessors — W. Smith, Grunow, etc. Recent study, with the aid of better objectives, has proved to me that they are in reality irresolvable costw. X. Abbreviate. Valve with considerable hyaline space, rounded, i Strias delicate> feebly radiate ■ N- brevis- abruptly diminuate . . ,].. , , „ , J \ Striae robust, strongly radiate . N. elegans N. brevis Greg. (Diat. of Clyde, p. 6, pi. 1, f. 4 ; H.V.H. Atl., pi. 11, f. 19*), plate 4, fig. 180. Valve elliptic, with apices diminuate-rostrate, rostrum very broad. Raphe surrounded by a rather broad hyaline zone, dilating round the central nodule into a considerable hyaline space, rounded, abruptly diminuate. Striae radiate, finely punctate, 14 in 1 c.d.m. Marine. — Washing of mussels (Deby). Very rare form. England, Scotland (Greg. ), Finmark, Bahusie. var. elliptica (H.V.H. Atl., pi. 11, f. 18*; = C. brevis var. vexans CI.), plate 4, fig. 181. This form, with rounded apices, not diminuate-rostrate, is much commoner than the type form. It is found in brackish water, but has not yet been found in Belgium. p 210 NAVICULA. N. elegans W.Sm. (S.B.D., i., p. 49, pi. 16, f. 137*), plate 27, fig. 761. Valve lanceolate, with apices diminuate, sub-acute. Central nodule sur- rounded by a considerable hyaline area. Stria; not reaching to the raphe, radiate, undulate ; apparently costiform, very vigorous, 6 or 7 in i c.d.m. Length, 7 to n c.d.m. Breadth, 3 to 3*5 c.d.m. Brackish water. — Not yet found in Belgium. Rather common in England. Marstrand ! (Sweden). XI. Perstriatse. r r 0) 3 I 3 s a o o'rt o > Valv T3 u '_> 3 T3 O (X < Median strire alter- nately long and short. Valve large, elliptic, oval, or subquadrangular. f Apices elongate, ros- I trate j ! Apices very gently diminuate, not ros- t trate ( Valve small, suborbiculate r Striae not alter- nately long and short. Valves with coarse puncta. ( Valve with rounded Apices ! h>'aline st5ace somewhat \ Valve wkh nan.ow rostrate. elongated pseudo- l_ stauios . Apices sub-acute I Valve regularly elliptic. Scattered puncta in centre of valve j Striae with distant l_ puncta . Valve with fine puncta, valve regularly elliptic . _ Apices produced, rostrate . e having two lunate sulci near the central nodule N. humerosa. N. latissima. N. scutelloides. N. granulata. N. Scandinavica. N. marina. N. Baileyana. N. fraudulenta. N. Scutum. N. pusilla. N. Schumanniana. I. Valve without lunate sulci near the central nodule. a. Apices not produced rostrate. a'. MEDIAN STRL« ALTERNATELY LONG AND SHORT. N. humerosa Breb. (in w.Sm., S.B.D., ii., p. 93; H.v.H. Atl., pl. 11, f. 20*; Type No. 117), plate 4, fig. 182. Valve linear-elliptic, with apices somewhat abruptly constricted, attenuate. Raphe surrounded by a narrow hyaline zone, somewhat dilated transversely NAVICULA. 211 round the central nodule. Striae distinctly granular, radiate, the median ones of unequal length, rather distant, the others very compact, about 9 in 1 c.d.m. Length, 5 to 7 c.d.m. Breadth, 2-5 to 3 c.d.m. Marine. — Blankenberghe (H.V. H. ; P. Petit). Great Britain (common), and probably or all the North Sea shores. This species, says Donkin (Brit. D.), is very variable in size and outline. The dry valve is colourless. N. latissima Greg. (T.M.S., 1856, iv., p. 40, pi. 5, f. 4; Ad. Schm. Atl., pi. 6, f. 7*), plate 27, fig. 762. Differs from the preceding by its larger size, its more rounded form, and its apices very slightly diminuate, not rostrate. Length, 10 c.d.m. Breadth, 5'5 c-dm- Marine.— Scheldt ; Blankenberghe (H.V.H. ). England, Scotland, Denmark, Finmark, Sweden. N. scutelloides W. Sm. (Q.j.m.s., 1856, iv., p. 4, pi. 1, f. 15*), plate 27, fig. 763. Valve small, suborbicular. Striae moniliform, strongly radiate, very distant, 7 or 8 in 1 c.d.m., reaching to the raphe. Fresh water.- — Not yet found in Belgium. England, Scotland, Ireland, Bahusie. aa'. MEDIAN STRLE NOT ALTERNATELY LONG AND SHORT. b. VALVE WITH COARSE PUNCTA. N. granulata Breb. Ms. (H.v.H. Atl., pi. n, f. 15*; in Types Nos. 74, 94, 116, 339, 369, 523, 549, 550), plate 4, fig. 183. Valve broad, elliptic or linear elliptic, with median portion sometimes slightly conctricted, apices abruptly attenuate, shortly rostrate. Raphe surrounded by a narrow hyaline zone, enlarged transversely round the central nodule. Striae radiate, 8 in i c.d.m., composed of very coarse puncta. Dry valve of a purple blue colour. Length, 6 to 9 c.d.m. Breadth, 2-5 to 4*5 c.d.m. Marine.— Ostend, Blankenberghe. England, Scotland, Ireland, France. var. maculosa. (A. macu/osa Dotik., Br, Diat., p. 25, pi. 5, f. 1*), plate 27, fig. 767. Valve linear-elliptic, narrow ; apices narrowly rostrate. Length, 6-5 c.d.m. Breadth, 2 c.d.rn. Marine. — England (Donk.), usually in company with N. humerosa. 2T2 NAVIGULA. N. Scandinavica (Lag.) Ad. Schm. (sub Stauroneis in Salltv. Bohuslan, p. 47 ; Ad. Schm. Nordsee, pi. 1, f. 29*), plate 27, fig. 764. Valve lanceolate, with apices produced-subrostrate. Striae radiant, reaching to the raphe, about 10 to 11*5 in 1 c.d.m., with strong puncta, shortened near the central nodule, where they leave a stauroneiform space, narrow, elongate. Length, 6-5 to 10-5 c.d.m. Breadth, 3 to 3-5 c.d.m. Marine. — Bahusie (Lag.). North Sea (Ad. Schm.). Note. — Most authors have confounded this species with N. lacustris Greg. According to authentic specimens of Gregory in our possession, N. lacustris is a form almost typical of N. Placentula Ehr. (Syn., pi. 8, f. 28). N. Baileyana Grun. (in Ad. Schm. Atl., pi. 6, f. 26*; N.granu- lata Bail, nee Breb.), plate 27, fig. 765. Valve elliptic or elliptic oval ; striae strongly granular, about 8 in 1 c.d.m. with approximate granules at the margin of the valve, but becoming scattered as they approach the raphe. Raphe sometimes enlarged and accompanied by a hyaline area, equally enlarged on each side of the valve. Central nodule elongated, surrounded by a stauroneiform hyaline area, more or less elongate, narrow. Length, 5 to 8 c.d.m. Breadth, 2-5 to 3*5 c.d.m. Marine. — North Sea (Hvidingsoe, Ad. Schm. ; Bahusie CI.). N. fraudulenta Ad. Schm. (in Atl, pi. 70, f. 60*), plate 27, fig. 766. Valve regularly elliptic ; stria; not reaching to the raphe, 10 in i c.d.m. at the middle of the valve, somewhat radiant, formed of rather strong granules, distant, leaving a small hyaline area round the central nodule. Length, about 3 c.d.m. Breadth, almost 2 c.d.m. Marine.— North Sea (Solsvig, Ad. Schm.). N. marina Ralfs. (in Pritch. inf., p. 9o3; h.v.h. Atl., pi. n, f. 16*; Type No. 118), plate 4, fig. 184. Valve broadly oval, with sub-acute apices. Raphe surrounded by a narrow irregular hyaline zone, somewhat enlarged round the central nodule. Stria; radiate, 10 or 11 in 1 c.d.m., formed of very coarse puncta. Length, 6 to 7 c.d.m. Breadth, 2-5 to 3-5 c.d.m. Marine? (Brackish water, according to Donkin). — Very rare : Washings of mussels (Debv). — England, Ireland, France. NAVICULA. 2 I b. VALVE WITH FINE PUNCTA. N. Scutum Schumann. ? (Preuss. D., p. 188, f. 45 ; H.v.H. Atl., pi. ii, f. 14*), P^te 4, fig. 185. Valve narrowly elliptic, with apices not attenuate. Raphe surrounded by a hyaline zone rather broad, irregular, enlarged round the central nodule. Terminal nodules robust. Striae feebly radiate, finely granular, 16 in 1 c.d.m. Length, 3 c.d.m. Breadth, 1 c.d.m. Freshwater. — Very rare? Manage (P. G.), Prussia, Spitzbergen. aa. Apices produced rostrate. N. pusilla W. Sm. ! (s.b.d. i., P. 52, pi. 17, f. 145; h.v.h. Atl., pi. 11, f. 17*; Type No. 119), plate 4, fig. 186. Valve varying from broadly oval to elliptic-lanceolate, with apices produced rostrate, rostrum truncate. Raphe surrounded by a small hyaline zone enlarged round the central nodule ; striae distinctly granular, the median often of unequal length, distant, about 10 in 1 c.d.m., the following ones more compact, less robust,, about 14 in 1 c.d.m., radiate. Length, 3-5 to 4*5 c.d.m. Breadth, about 2 c.d.m. Brackish water. — Antwerp, England, Ireland, Denmark. II. Valve having two lunate sulci near the central nodule. N. Schumanniana Grun. (N. Trochus (Ehr) ? n Schumann Preus. D., p. iS9; pi. 2, f. 52 ; H.V.H. Atl., pi. 11, f. 21* = Coloneis CI ), plate 4, fig. 187. Valve narrowly elliptic, with median portion strongly inflated ; raphe surrounded by a feeble hyaline zone, conspicuously enlarged round the central nodule, and showing there, on each side of the nodule, in the longitudinal direction, a deep lunate sulcus; striae radiate, about 16 or 17 in 1 c.d.m. Length, about 3 c.d.m. Breadth at the median inflation, 1 c.d.m. Freshwater. — Rare. Antwerp (P. G.), Brussels (Delogne). XII. Johnsonieae. N. JohnSOnii (W. Sm.)! (Pinnularia Johnsonii IV. Sm., S.B.D., i., p. 58, pi. 19, f. 179; H.V.H. Atl. Supp., f. 28*), plate 4, fig. 188. 2T4 NAVICULA. Valve very elongate, linear, gently inflated at the median portion and at the apices; raphe not surrounded by a hyaline area; longitudinal and transverse stria? delicate, cutting one another at right angles, equally distant, about 20 in 1 c.d.rn. Length, 13 to 14 c.d.m. Breadth at the median portion, 1 c.d m. Brackish water.— Not yet found in Belgium. England, Ireland, France. var. Belgica H.V.H. (H.V.H. Atl. Supp., f. 29*), plate 4, fig. 189. Much smaller than the type form and with very pronounced inflations. 24 striae in 1 c.d.m. Length, 6 to 7 c.d.m. Breadth at the central inflation, 075 c.d.m. Brackish water. — Ostend (Charles Petit). XIII. Crassinerves. { Valve lanceolate, with apices not rostrate-capitate . . N. cuspidata. -{ Valve with apices rostrate-subcapitate *. N. ambigua. (. Valve rostrate-subcapitate, showing transverse thickenings . . forma craticula. N. CUSpidata KlltZ. (Baa, p. 94, pi. 11, f. 24 and 37; H.V.H. Atl., pi. 12, f. 4*), plate 4, fig. 190. Valve broadly lanceolate, with apices gently inflated, not rostrate ; trans- verse striae gently radiate, almost perpendicular to raphe, fine, reaching almost to the raphe, 14 in 1 c.d.m. Longitudinal striae fine and more compact. Length, about 9 c.d.m. Breadth, 2-3 c.d.m. Fresh water. — Common throughout Europe. var. halophila Grun. (H.V.H. Atl. Supp., f. 30*; in Type No. 12), plate 4, fig. 191. Narrow, very small: about 5 c.d.m.; striae delicate, about 16 in 1 c.d.m., radiate near the median portion, convergent at apices. Brackish water. — Blankenberghe. N. ambigua Ehr, (Amer., 1843, p. 129, pi. II. 2, f. 9; H.V.H. Atl., pi. 12, f. 5*; Type No. 121), plate 4, fig. 192. Differs from the preceding, of which it is probably only a variety, by its smaller size, and its apices which are rostrate-capitate. Length, 6 to 7 c.d.m. Breadth, 1*5 c.d.m. Fresh water.— Common throughout Europe. forma craticula. (H.V.H. Atl., pi. 12, f. 6*; Type No. 122), plate 4> fig- 193- Valve showing transverse thickenings. NAVICULA. 2 I 5 There is shewn in fig. 193, on the right moiety of the specimen, the fine striae which only exist on the surface of the valve, and on the left robust stride, strongly radiate, which are found in a deeper layer, probably on the interior surface of the valve. Mixed with the type form, but rare. Louvain and Manage (P. G. ). Note. — The forms above described were included by my late excellent friend Mr. de Brebisson in his genus Van Heurckia. The examination which I have made with better objectives than those in existence at the time de Bre'bisson published his Work, has convinced me that the raphe is simple, and that therefore these forms cannot be included in the said genus. XIII bis. Fusiformes. N. fusiformis Grun. (M.M.J., 1877, xviii., p. 178, pi. 195, f. n*)3 plate 27, fig. 768. Valve narrowly lanceolate, infinitesimal])' attenuate up to acute apices. Transverse stria?, 33 in 1 c.d.m. Longitudinal striae, 36 in 1 c.d.m. Raphe thick, very distinct, central nodule indistinct. Length, 11 to 15 c.d.m. Marine. — Hitherto only found in Honduras. var. ostrearia (Gaill.) H.V.H. (JV. fusiformis vcr. ostrcaria Grun. in H.V.H. Syn., pi. 14, f. 33*). plate 27, fig. 769. Valve small ; transverse striae, 36 in 1 c.d.m., excessively delicate, scarcely visible. Length, 6*25 to 7^25 c.d.m. Breadth, 6 to 7 mill. d.m. Marine. — North Sea. Sweden and probably other places. This form lives in oyster beds and colours the oysters green. By the side of N. fusiformis are placed two forms not very well known, which Prof. Cleve includes in his group Navicular Entoloice and which are distinguished from the Fusiformes by their lanceolate axial area. They are : — N. inornata Grun. (Arc. Diat., p. 124, pi. 3, f. 56*), plate 27, fig. 770. Valve fusiform, convex. Striae delicate, almost parallel, 19 to 21 at the middle of the valve, 23 or 24 in 1 c.d.m. at the apices, leaving a longitudinal area, narrow, lanceolate, and appearing to be crossed by two longitudinal lines, which however are illusory. Length, 5 to 9 c.d.m. Breadth, about 1 cd.m. Marine. — English Channel. Finmark. Bahusie. 2l6 N.WICULA. N. fusoides Grun. (Arc. Diat., p. 46, without figure). Valve narrow, linear-lanceolate, with apices more or less obtuse. Axial area narrow. Striae, 21 to 25 in 1 c.d.m., gently radiant, crossed by two true longitudinal lines. Length. 5 to 12 c.d.m. Breadth, 7 to 12 mill. d.m. Marine. — Bahusie (Grun.). XIV. Sculpteae. Valve with apices rostrate, no median depression forming a pseudo-stauros N. sculpta. Valve with apices rostrate-capitate, with median depression simulating a pseudo-stauros . . . . . . N. sphseropliora. \ N. sculpta Ehr. (Mikr., pi. x. i, f. 5; h.v.h. Atl., pi. 12, f. 1*; Type No. 123), plate 4, fig. 194. Valve elliptic, with tapering apices, then longly rostrate, rostrum obtuse. Raphe surrounded by a considerable hyaline zone. Striae feebly radiate, 15 to 16 in 1 c.d.m., formed of coarse puncta, interrupted near the raphe by a broad depression of the valve in such a manner as to leave against it only a single row of granules. The depression also continues — but not so deep — near one of the margins of the valve in the form of a unilateral, indistinct, pseudo- stauros. Length, 7 to 8 c.d.m. Breadth, 2-5 c.d.m. Fresh and brackish water.— Rare. Parck near Louvain (P.G.), Blankenberghe. England, Ireland, France, Norway. N. sphaerophora Kutz. (Bac, p. 95, pi. 4, f. 17; H.V.H. Atl., pi. 12, f. 2 and 3* : Type No. 124), plate 4, fig. 195. Valve elliptic-lanceolate, with apices rostrate-capitate. Raphe surrounded by a considerable hyaline area. Striae, 16 in 1 c.d.m., gently radiate, granular, interrupted by narrow longitudinal depressions and by a broad transverse depression, forming a very conspicuous pseudo-stauros. Length, 5^5 to 8 c.d.m. Breadth, 175 to 2 c.d.m. Fresh water. — Not very common. Antwerp. Brussels (Delogne). Found throughout Europe. Probably only a variety of the preceding. XV. Serianteae. f Valve lanceolate, sometimes subrhomboidal, with subacute apices . . N. serians. < Valve lanceolate, narrow, with apices rostrate-capitate . . . N. exilis. I Valve cruciform .... . N. follis. NAVICULA. 217 N. serians Breb. (in Kutz. Baa, p. 92, pi. 3c, f. 23 ; H.v.H. Atl, pi. 12, f. 7* ; in Type No. 125), plate 4, fig. 196. Valve lanceolate. Raphe surrounded by a rather broad hyaline zone, somewhat dilated round the central nodule, which is coarse and round. Striae fine, about 24 in 1 c.d.m., feebly radiate, formed of elongate beads which, by being arranged at some distance apart, appear like irregular longitudinal lines. Length, 6 to 8 c.d.m. Breadth, 1*5 c.d.m. Boggy pools. — Rare. Calmpthout (Deby) ; Tete de Flandre at Antwerp (H.V.H.) ; Ard. Li£g. (De Wild. ). England, Scotland, Ireland, France. var. brachysira. (JV. brachysira Breb., H.V.H. Atl. Supp., f. 126*; Types Nos. 126 and 127), plate 4, fig. 197. Valve subrhomboidal, with subacute apices. Freshwater. — Cornimont, Bouillon (Del.). N. exilis Grun. (in H.V.H. Atl., pi. 12, f. n and 12* 1 Type No. 128), plate 4, fig. 198. Valve lanceolate, narrow, with apices rostrate-capitate. Striation, both in structure and direction, analogous to that of N. serians, to which it is allied by infinitesimal gradation (see H.V.H. Atl., pi. 12. f. 10); about 30 striae in 1 c.d.m. Length, 23 to 3 c.d.m. Breadth, about 0*5 c.d.m. Fresh water. — Ard. Lieg. (De Wild.). Ireland. N. follis Ehr. (Inf., 1S38, p. 179; Mikr., pi. XVI. 1, f. 14; Donk. Br. D., p. 44, pi. 6, f. 15*; in Type No. 274), plate 27, fig. 771. Valve small, cruciform, with costae incurved and gently inflated, apices obtuse. Puncta forming uninterrupted lines in zig-zag in axial illumination, but reduced in oblique illumination to fine stride, radiate, irregularly punctate, about 25 in 1 c.d.m. Raphe thick, central nodule elongate, surrounded by a rhomboidal hjaline space. Length, about 4 c.d.m. Breadth at central inflation, 2 c.d.m. Freshwater. — Rare. Near Heigham, Norfolk (Kitton). Loch. Kinnord (Davidson). Loch Oich, fossil deposit (Donkin). Loch Canmor, Scotland (Coll. Weissfl. !) Frico, nr. Christiansund, Norway (Coll. W. Arnott !). XVI. Formosse. Striae everywhere marginal . . . . . N. formosa. f Zone feebly dilated ( Valve narrowly elliptic . . N. Liburnica. round the central < nodule. ( Valve oval, elliptic . . N. latiuscula. Stria; not ; marginal. \ y r ,-, , / Dilatation in form of rounded area . N. permagna. round the central < -,-.•, . .■ -j Ui u , -, J Dilatation very considerable, sub- no e" v, quadrangular . . . N. amphisbaena. 21 8 NAVICULA. N. formosa Greg. (T.M.S., 1856, p. 42; h.v.h. Atl., pi. n, f. 2* ; in Type No. 105 = Caloneis formosa mr. Holmiensis C/.), plate 5, fig. 199. Valve linear, elliptic, with apices somewhat attenuate obtuse. Raphe sur- rounded by a broad hyaline zone, elliptic lanceolate ; terminal nodules robust, central nodule lateral. Marginal striae robust, finely divided transversely, somewhat radiate, crossed by a narrow sulcus rather distant from the margins, about 10 in 1 c.d.m. Length, about 14 c.d.m. Breadth, about 3 c.d.m. Marine and brackish water. — Scheldt at Antwerp. England, Scotland, Ireland, Denmark, Bahusie. N. Liburnica Grun. (Wien. Verh., i860, p. 547, pi. 1, f. 25; H.V.H. Atl., pi. 11, f. 3*; Type No. 133 = Cal formosa Cl.\ plate 5, fig. 201. Differs from the preceding by its subacute apices, its smaller size, narrow hyaline zone, and its more approximate stria? (12 in 1 c.d.m.). Length, 9 to 10 c.d.m. Breadth, 2 c.d.m. Marine.— Blankenberghe (H.V.H. ). Ireland (O'M.). Yarmouth, England (Kitton). N. latiuscula Kiitz. (Bac, p. 93, pi. 5, f. 11 : N. patula IV. Sm.I S.B.D. i., p. 49, pi. 16, f. 182 ; H.V.H. Atl., Supp. pi., pi. B., f. 29^*3 Type 906), plate 5, fig. 200. Valve broadly oblong or elliptic lanceolate with apices obtuse, rounded. Stria? finely punctate, 14 in i c.d.m., not reaching to the raphe, scarcely radiate ; raphe surrounded by a hyaline area inflated at the central nodule, which is elongated, somewhat arcuate. Length, about 15 c.d.m. Breadth, about 3 c.d.m. Fresh and brackish water.— Antwerp, Tete de Flandre (H.V.H. ). Found throughout Europe. N. permagna Bailey. (Smithson. Contrib., 1850, Bail. Micros. Observ. in Georgia, S. Carolina and Florida, p. 40, pi. 2, f. 28, 38 ; T.M.S., 1866, vi., n.s., p. 127, pi. 12, f. 18-21 ; H.V.H. Atl., pi. 11, f. i*j Type No. 134), plate 5, fig. 202. Valve broadly lanceolate, with subacute apices. Central nodule lateral, terminal nodules robust. Raphe surrounded by a broad hyaline zone dilated into a round area at the median portion. Stria? fine, about 12 in 1 c.d.m., 219 radiate, finely divided transversely and interrupted near the margin of the valve by a rather broad depression, of which the margins have the appearance of double sulcus. Length, about 14 c.d.m. Breadth, 4 c.d.m. Brackish water. — Rare, Antwerp (H.V.H.). The type form does not appear to have yet been found in any other part of Europe. The forma parva has been found at Schleswig, and a var. by Kitton at Breydon, Norfolk, England. N. amphisbaena Bory. (Encyciop. Method., 1824; h.v.h. Atl., pi. 11, f. 7*; Type No. 130), plate 5, fig. 203. Valve broadly elliptic, with apices strongly rostrate capitate. Central nodule lateral, terminal nodules robust. Raphe surrounded by a considerable hyaline zone, dilated in the middle of the valve into a broad space lanceolate- subquadrangular. Stria; radiate, about 14 in 1 c.d.m., finely divided trans- versely, interrupted by a rather broad submarginal sulcus. Length 6 to 7 c.d.m. Breadth, 225 c.d.m. Fresh or somewhat brackish water. — Antwerp, &c. Throughout Europe. var. subsalina. (H.V.H. Atl., pi. 11, f. 6* ; Type No. 131), plate 5, fig. 204. Apices gently acuminate, not rostrate capitate. Brackish water. — Banks of the Scheldt at Antwerp. England. forma major. (H.V.H. Atl., pi. 11, f. 4*), plate 5, fig. 205. Much larger, valve lanceolate, infinitesimally attenuate as far as the apices, which are very gently acuminate. Length, 10 c.d.m. Breadth, about 3 c.d.m. Brackish water. — Scheldt at Antwerp. var. Fenzlii. (H.V.H. Atl., pi. 11, f. 5*), plate 5, fig. 206. Valve broader, with apices scarcely acuminate. XVII. Limosae. f No pseudo stauros, valve with three well marked inflations . . N. limosa. Valve with three inflations slightly marked . N. ventricosa. { A pseudo stauros Valve linear, without inflations . . N. fontinalls. N. limosa KlltZ. (Baa, p. 101; H.V.H. Atl., pi. 12, f. 18*; Type No. 135 : Caloneis Silicula (Ehr.) CI.); plate 5, fig. 207. Valve narrow, linear, with three undulations, equal, feeble, with rounded apices. Raphe surrounded by a lanceolate hyaline zone, somewhat enlarged at the median portion. Ctntral nodule somewhat lateral; terminal nodules 2 20 NAVICULA. robust. Striae 16 or 17 in 1 c.d.m., somewhat convergent at the median portion, feebly radiate at the apices, crossed by a narrow sulcus approximate to the margins of the valve, the outlines of which it follows. Length, 7 to 8 c.d.m. Breadth, about 1*5 c.d.m. Fresh water— Louvain (P.G.). Laviot (Del.), Antwerp (H.V.H.) Aid. Lieg. (De Wild.). Probably not rare, for it has been found throughout Europe. var. gibberula. (N. gibberula Kiitz. ; H.V.H. Atl., pi. 12, f. 19*; Caloneis Siltcula {Ehr.) CI. var. gibberula); plate 5, fig. 208. Smaller, valve with more marked inflations, apices cuneate. Length, 4-5 to 5 c.d.m. Like the preceding, throughout Europe. N. ventricosa (Ehr.?) Donkin. (Br. D., p. 74, pi. 12, f. 7; H.V.H. Atl., pi. 12, f. 24*; Cal. Silicilla (Ehr.) CI. var. ventricosa), plate 5, fig. 209. Differs from N. linwsa by its inflations being scarcely noticeable, its finer striae, 18 to 20 in 1 c.d.m., and by the stauroneiform hyaline area which surrounds the central nodule. Length, about 6 c.d.m. Breadth, 1*25 c.d.m. Fresh water. — Antwerp, etc. — As in the preceding, var. minuta. (H.V.H. Atl., pi. 12, f. 26*); plate 5, fig. 210. Very small (2-5 c.d.m. in length), with more marked inflations ; pseudo stauros broader, and apices somewhat cuneate, 21 striae in 1 c.d.m. Fresh water. — Louvain (P.G.). Ard. Lieg. (De Wild.). N. fontinalis Grun. (H.V.H. Atl., pi. 12, f. 33*: Caloneis fascial a ( Lag. ) Cleve) ; plate 5, fig. 211. Valve linear, with rounded apices. Raphe surrounded by a lanceolate hyaline zone, enlarged at the middle of the valve into a very broad pseudo- stauroS; Striae feebly radiate, 24 to 26 in 1 c.d.m., crossed by a sulcus almost marginal. Length, about 2*5 c.d.m. Breadth, 0-5 c.d.m. Fresh water. — Brussels (Delogne). XVIII. Affines. Raphe with median apices curved like a crook, subparallel, with elongated puncta, interrupted near the margins by a deep sulcus . . . N. Iridis. N. Iridis Ehr. (Kiitz. Bac, p. 92, pi. 28, f. 42, N. firma IV. Sm.; H.V.H. Atl., pi. 13, f.i*), plate 5, fig. 212. Valve linear elliptic, with rounded apices. Raphe with median apices curved like a crook, in opposite directions, surrounded by a hyaline zone NAV1CULA. 22 1 dilated transversely round the central nodule, which is placed somewhat obliquely ; terminal nodules robust. Strice fine with elongated puncta, about 1 6 in i c.d.m, subparallel, somewhat oblique, interrupted near the margins by a deep sulcus, which terminates at the anterior part of the terminal nodules. Length, to to 17 c.d.m. Breadth, 2^25 to 3 c.d.m. Fresh water. — Pleinevaux (Delogne), Ard. Lieg. (De Wild.). England, Ireland, Germany, Finland (Cleve), etc. var. amphigomphus Ehr. (H.V.H. Atl., pi. 13, f. 2* ; in Type No. 67), plate 5, fig. 213. Smaller, with cuneate apices. Fresh water. — Ard. Lieg. (De Wild.). England, Ireland. var. firma Kutz. (in H.V.H. 's Type No. 67). Differs from the preceding form in the apices, being rounded and not cuneate. All intermediate forms are found in the same gathering. The striae (in Type No. 136) have otten an oblique direction. Fresh water. — This variety as well as the following are found here and there throughout Europe. var. amphirhynchus Ehr. (H.V.H. Atl., pi. 13, f. 5*), plate 5, fig. 214. Valve linear, narrow, with apices broadly and longly rostrate, rostrum slightly inflated at the apex. Fresh water. var. dubia Ehr. (H.V.H. Atl. Supp., f. 32* ; in Type No. 79), plate 5, fig. 215. Valve linear, short, rather broad, with apices broadly rostrate, rostrum not inflated. 20 striae in 1 c.d.m. Length, 375 c.d.m. Breadth, about 1 c.d.m. Fresh water. — La Hulpe (Del.). var. undulata Grun. (H.V.H. Atl., pi. 13, f. 6*), plate 5, fig. 216. Differs from the amphirhynchus in its margins being tri-undulate. Fresh water. — Rather rare? Antwerp. var. affinis. (H.V.H. Atl., pi. 13, f. 4*; Type No. 136), plate 5, fig. 217. Valve linear, with apices more or less rostrate capitate. Fresh water. var. producta. (H.V.H. Atl., pi. 13, f. 3*), plate 5, fig. 218. Valve elliptic, with apices strongly rostrate capitate. Fresh water. Many of these forms are often met with together. The Revd. P. A. Gautier has observed that in all these forms, after death, the endochrome divides into four parts ; during life the commencement of a division can even be observed in the middle of the endochrome. N. Iridis and its various forms constitute the genus Neidium of Messrs. Pfitzer and Cleve. N. Liber. 22 2 • NAVICULA. XIX. Lineares. fc, ■ , ,• f Margins straight, apices rounded Stnneextendingover | ° 6 . the whole valve . *| ,^ . , . .. ,. ... .. l_ Margins excavated at the median portion . . var. bicuneata. C Pseudo-stauros very broad ; 13-16 in 1 c.d.m ; Striae interrupted by J sulcus conspicuous . . N. consimilis. a pseudo-stauros . ~j D , . . . , ^ I Pseudo-stauros narrow, 19-21 striae in 1 c.d.m. ; { sulcus less visible . . . . . N. aemula. N. Liber W. Sm. (S.b.d., i., p. 48, pi. 16, f. 133; h.v.h. Atl., pi. 12, f. 36* ; Type No. 137), plate 5, fig. 219. Valve linear narrow, with rounded apices. Raphe with a hyaline and but slightly marked zone. Central nodule surrounded by a small rounded hyaline area ; terminal nodules somewhat distant from the apices, curved like a comma. Striae fine, parallel, about 18 in 1 c.d.m., crossed by a longitudinal sulcus flexed towards the margin at the median portion. Length, about 8 c.d.m. Breadth, 1.5 c.d.m. Marine. — Washings of mussels (Deby.) Blankenberghe, Scheldt (H.V. H. ). England (W. Sm., Kitton, Comber, Norman). Ireland (O'Meara), and probably on all the North Sea Coasts. var. linearis. (H.V.H. Atl., pi. 12, f. 35), plate 5, fig. 220. Much smaller and narrower. Length, 5.5 c.d.m. Breadth, about 1 c.d.m. var. bicuneata Grun. (N. maxima Greg., Q.J. M.S., 1856, hi., p. 41, pi. 4, f. 19 ; T.M.S., 1856, iv., p. 39, pi, 5, f. 2*),' plate 35, fig. 910. Differs from the type form by its greater breadth, by its sides being somewhat excavated at the median portion, and its apices somewhat cuneate. Valves large, broadly linear, oblong, with margins gently excavated at the median portion, apices cuneate, obtuse. Transverse striae 13-14 in 1 c.d.m., reaching to the raphe, parallel, crossed by a sulcus at the middle of their length. Length, 10 c.d.m. Breadth, 2 to 2.5 c.d.m. Marine. — Scotland (Gregory, Donkin), Ireland (O'Meara). Mr. Grunow believes that this form ought to be considered as a variety of N. Liber. N. COnsimilis Ad. Schm. (Nordsee Diat., p. 91, pi. 2, f. 46*), plate 27, fig. 773. Has been found in the North Sea by Dr. A. Schmidt. It is distinguished from JV. Liber by stronger strise (13 to 16 in 1 c.d.m.), interrupted in the median portion of the valve by a very broad hyaline space stauroneiform, and again by more robust sulci, NAVICULA. 223 N. semilla Ad. Schm. (Nordsee, p. 91, pi. 2, f. 47*; JV. subdivisa Grun., Arc. Diat, p. 29, pi. i, f. 20), plate 27, fig. 772. Is only differentiated from N. consimilis by its smaller size, by its stride being more approximate (19 to 21 in 1 c.d.m.) and by the marginal sulcus being less apparent. This form has been recorded from Normandy and the Baltic. XX. Americanae. Striae marginal throughout, and much shortened at the median portion of the valv,5 .......... N. Americana. N. Americana Ehr. (Mikr., Pi. 11. 2, f. 16; h.v.h Atl., pi. 12, f. 37*; Type No. 138), plate 5, fig. 221. Valve linear obbng, with rounded apices, slightly constricted near the middle. Raphe robust, surrounded by a hyaline zone, occupying the moiety of the valve and further dilated round the central nodule, which is robust and marked by one or two pore-like puncta near its lower third. Marginal striae feebly radiate, finely punctate, 16 in 1 c.d.m. Length, about 9*5 c.d.m. Breadth at the median constriction 2*5 c.d.m. ; at the broadest portion 275 c.d.m. Fresh water.— Very rare. Antwerp (Belleroche !), Ireland (OM.), Loch Kinnord, Scotland (Davidson). XXI. Bacilleae. Valve linear, without any considerable inflations. r f No pseudo-stauros, terminal nodules Terminal nodules straight, not - prolonged la- terally . surrounded by a considerable hya- line area I A pseudo-stauros, terminal nodules without any considerable hyaline L area ..... Terminal nodules straight, comma-like Terminal nodules curved later- ally like a crook Valve broadly linear, central nodule surrounded by a considerable hya- line area .... N. Bacillum. N. bacilliformis. N. subhamulaba. N. pseudo-bacillum Valve narrowly linear, often very feebly inflated at the median por- tion ; no considerable hyaline area N. laevissima. Valve f Striae almost submarginal, no false stauros, terminal inflated in nodules curved like a crook unilaterally . . N. Hebes. the middle -1 and at the | Striae extending up to the raphe — a false stauros — ter- apices. I, niinal nodules curved like a crook bilaterally . . K. Pupula, 224 NAVICULA. N. Bacillum Ehr. (Mikr., pi. 15, A., f. 38; H.v.H. Atl, pi. 13, f. 8*; in Type No. 548), plate 5, fig. 222. Valve linear, with apices rounded, thickened, smooth. Raphe surrounded by a very narrow hyaline area, slightly enlarged round the central nodule and at the apices of the valve. Striae slightly radiate, finely granular, 14 in 1 c.d.m. at the median portion of the valve, and about 17 at the apices. Length, 5-5 c.d.m. Breadth, 1-5 c.d.m. Fresh water. — Here and there throughout Europe. forma minor. (H.V.H. Atl., pi. 13, f. 10*), plate 5, fig. 223. Smaller and narrower, dimensions amounting to not more than about a moiety of the preceding. Striae finer, 16 in 1 c.d.m. at the middle, 20 at the apices of the valve. Fresh water. — Brussels Botanical Gardens (Delogne). N. bacilliformis Grun. (in CI. and Gr. Arct. D., 1880, p. 44, pi. 2, f. 51 ; H.V.H. Atl., pi. is, f. 11*), plate 27, fig. 774. Valve linear, with apices rounded. Raphe surrounded by a hyaline zone, very narrow, enlarged into a stauros round the central nodule. Striae feebly radiate, convergent towards the apex of the valve, 10 to 15 in 1 c.d.m. Length, 3-5 to 4^5 c.d.m. Breadth, about 1 c.d.m. Fresh water?— Ard. Lieg. (De Wild.). Hickling, Norfolk, England (Kitton) ; Dover, England (Grun.). N. subhamulata Grun. ! (H.v.H. Atl., pi. 13, f. 14*) plate 5, fig. 225. Valve linear, somewhat inflated at the median portion, with rounded apices. Raphe surrounded by a very slight hyaline zone, somewhat dilated round the central nodule. Terminal nodules comma-shaped. Striae some- what radiate, very feeble, about 26 in 1 c.d.m. Girdle face with undulated margins. Length, 2 c.d.m. Breadth, somewhat more than -5 c.d.m. Fresh water. — Brussels (Delogne). N. pseudo-Bacillum Grun. ! (H.V.H. Atl., pi. 13, f. 9*), plate 5, fig. 224. Differs from JV. Bacillum by its larger hyaline area, its terminal nodules prolonged laterally like a comma on each side and its finer striae, 21 in 1 c.d.m. in the middle, and 24 at the apices of the valve. Length, 4^5 c.d.m. Breadth, about 1-5 c.d.m. Freshwater. — Louvain (P.G.). Ard. Li£g. (DeWild.). NAVICULA. 225 N. levissima (Kutz. ?) Grun. (H.V.H. Atl., Pi. 13, f. 13*), plate 27, fig. 775. Valve linear, with rounded apices, at the median porrion often somewhat inflated, stride slightly radiate-convergent, not reaching to the raphe, 13 in 1 c.d.m. at the median portion of the valve, 20 in 1 c.d.m. near the apices. Length, about 3 c.d.m. Breadth, 75 c.d.m. Fresh and brackish water. — Ard. Lieg. (De Wild.) England, France. N. Hebes Ralfs. (in Pritch. Inf., p. 896; N. obtusi IV. Sm., S.B.D., i., p. 50, pi. 16, f. 140*; H.V.H. Type No. 75), plate 27, fig. 776. Valve oblong elliptic, contracted towards the apices which are inflated, rounded, sometimes subtruncate. Striae 12 to T4-5 in 1 c.d.m., snbmarg.nal, punctate, leaving round the raphe a considerable hyaline area, which is further dilated round the central and terminal nodules. Length, about 6 c.d.m. Breadth, 2 c.d.m. Fresh water.— Ireland (W. Sm. ; O'M.). Scotland (Donkin ; W. Sm.). N. Pupula KlltZ. ! (Bac, p. 93, pi. 30, f. 40; H.V.H. Atl., pi. 13, f. 15-16*), plate 5, fig. 226. Valve linear, inflated at the median portion and at the apices, which are rounded. Raphe surrounded by a narrow hyaline zone, abruptly enlarged into a pseudo-stauros round the central nodule. Terminal nodules prolonged laterally. Striae radiate, fine, 21 to 24 in 1 c.d.m. Length, r6 to 3-6 c.d.m. Breadth, *5 to i'o c.d.m. Fresh water. — Louvain (P.G.), Antwerp. France. 226 NAVICULA. XXII. Minutissimae. I. Frustules not united into bands. f Valve with coarse striae simulating costee i I I -s -! -° 8 *c (73 Valves ( Valve somewhat inflated at the median portion having ( Valve linear-elliptic ( Valve elliptic a Valve pseudo- not stauros. L inflated. f f Valve lanceolate, narrow, stria; radiate, very dis Valve without a pseudo- stauros. tinct N. incerta, N. Seminulum. N. minima. N. atomoides. . N. Falaisensis. 1 Valve lanceolate, ( Marine : 24 — 30 since in 1 rather bioad, c.d.m. . . . N. Bahusiensis. striae scarcely J Valve radiant, the ; lanceolate. -| median more | Fresh water : 36 strire in 1 apparent. L c.d.m. . . . N. minuscula. Valve rather broad, striae radiate, alternately long and short at the median portion of the valve, apices obtuse . . . . N. cocconeiformis. Valve very narrow, striae parallel, apices not sub- L rostrate . . . . N. Bulnheimii. " Valve deeply constricted at the median portion . N. binodis. ( Valve inflated at the median portion . N. perpusilla. f Valve linear elongate . N. lepidula. I Valve elliptic, sublanceo- Valve not lanceolate. Valve not con- -; stricted. I Valve not inflated. late N. exilissima. I Valve elliptic, suborbicu- i_ late . . N. Atomus. II. Frustules united in bands. ' Valve with median and terminal portions inflated ... N. contenta. ,, , ( Valve linear-elliptic, with margin furnished with coarse, distant beads . N. Gallica. Valve J ' not so. I vklve linear, inflated in the middle, without coarse beads at the margin N. Flotowii. /. Frustules not united in long bands. a. Valve furnished with costas. N. incerta Grun. ! (H.V.H. Atl., pi. 14, £ 43*). Plate 5. fiS- 227- Valve linear lanceolate, with apices somewhat produced ; striae in form of robust costae, reaching almost to the raphe, somewhat distant, about 15 in i c.d.m. Length, 1*5 c.d.m. Breadth, -6 cd.m. Marine. — Blankenberghe. NAVICULA. 22 7 a a. Valve without costae. b. VALVE FURNISHED WITH A PSEUDO-STAUROS N. Seminulum Grun. ! (H.v.H. Atl., pi. 14, f. 9*; Type No. 143), Pla*e 5, fig- 228. Valve almost linear, with median portion inflated, apices obtuse rounded ; striae radiate, rather robust, punctate, 20 in 1 c.d.m., reaching almost to the raphe, much shortened near the central nodule, where their limited length produces a stauroneiform blank space. Length, about 1.5 c.d.m. Breadth •4 c.d.m. Fresh water. — Brussels (Delogne). N. minima Grun. ! (H.v.H. Atl., pi. 14, f. 15*; Type No. 142), plate 5, fig. 229. Valve linear, with rounded apices ; stria? radiate, 26 in 1 c.d.m, reaching to the raphe, the median ones much shortened, and considerably more distant. Length, 1*5 c.d.m. Breadth, '45 c.d.m. Fresh water. — Brussels, in a water bottle (Del.). N. atomoides Grun. ! (H.V.H. Atl., pi. 14, fig. n*; in Type No. 219), plate 5, fig. 230. Valve elliptic ; striae fine, feebly radiate, 27 to 30 in 1 c.d.m,, reaching almost to the raphe, but shortened near the central nodule, where they form a pseudo-stauros of greater or less length. Fruslules often united into a band of 3 or 4. Length, about '8 c.d.m. Breadth, about '4. c.d.m. Fresh water. — Antwerp, in an aquarium, where the species has been maintained for several years. Prof. Cleve makes this form a simple variety of N. minima. b b. VALVE WITHOUT FSEUDO-STAUROS. N. Atomus Nsegeli. (H.v.H. Atl, pi. 14, f. 24* ; Type No. 149), plate 5, fig. 231. Valve elliptic, feebly silicious ; raphe robust ; striae fine, strongly radiate, about 30 in i c.d.m. Length, *4 to -8 c.d.m. Breadth, -25 to "4 c.d.m. Humid positions. — Brussels (Delogne), Antwerp. 228 NAVICULA. N. Falaisensis Grun. ! (H.v.H. Atl., pi. 14, f. 5* ; in Type Nos. 127 and 348), plate 5, fig. 232. Valve narrowly lanceolate, apices subrostrate ; striae rather robust, about 20 in 1 c.d.m., not quite reaching to the raphe, and leaving around the central nodule a small rounded hyaline area. Length, about 2*5 c.d.m. Fresh water, — Bouillon (Del.). N. minuscula Grun. (in H.v.H. Syn., pi. 14, f. 3*), plate 27, fig. 777. Valve lanceolate, with subrostrate apices ; striae reaching to the raphe, scarcely radiant, about 36 in 1 c.d.m., the median ones somewhat distant, and consequently more distinct. Length, about 1*25 to 175 c.d.m. Breadth, about o-5 c.d.m. Fresh water. — Ditch at Kiel, near Antwerp (H.V.H.). N. Bahusiensis Grun. (in H.V.H. Syn., pi. 14, f. 2*), plate 27, fig. 778. Differs from the preceding by its larger size (1*5 to 2-o c.d.m. in length), its more vigorous striation (24 to 30 striae in 1 c.d.m.), and its habitat (salt water). Sweden. — (Lysekl, Grun.). N. cocconeiformis Greg. (Q.J.M.S., 1856, iv., p. 6, pi. :, f. 22 ; H.V.H. Atl., pi. 14, f. 1* ; Type No. 140), plate 27, fig. 779. Valve small, lanceolate, inflated at the median portion with obtuse apices. Raphe bordered by a narrow hyaline area, somewhat dilated round the central nodule. Striae very finely radiate, convergent, 28 to 30 in 1 c.d.m. at the apices of the valve, 18 in 1 c.d.m. round the central nodule; the latter alternately long and short. Length, about 3^5 c.d.m. Breadth, 1-25 c.d.m- at the median inflation. Fresh water. — Scotland, Ireland, etc. N. Bulnheimii Grun. ! (H.v.H. Atl., pi. 14, f. 6a*), plate 5, fig. 233- Valve very narrowly lanceolate, with subacute apices ; striae feeble, parallel, about 30 in i c.d.m. The two median striae more vigorous than the others. Length about 2 c.d.m. Marine ? Not yet found in Belgium. var. Belgica Grun. ! (in Type No. 113). Valves somewhat more obtuse, with girdle face broader and con- necting zone finely striated lengthwise. Marine. — Ostend. NAVICULA. 229 N. exilissima Grun. ! (H.v.H. Atl., pi. 14, f. 30*; in Type No. 141), plate 5, fig. 234. Valve linear-subelliptic ; striae fine, radiate, about 40 1 c.d.m., the median ones somewhat more distant, details indistinct even with homogeneous objectives, and in Prof. H. L. Smith's yellow medium. Length, from "5 to i*o c.d.m. Fresh water. — Groenendael (Delogne) ; Ard. Li^g. (DeWild.). N. binodis (Ehr., 1840) W. Sm. (S.B.D., i., p. 53, pi. 17, f. 159 ; H.V.H. Atl. Supp., f. t,3* ; in Type No. 71), plate 5, fig. 235. Valve oblong, strongly constricted at the median portion, apices rostrate capitate ; striae reaching almost to the raphe, feebly radiate, very delicate, about 30 in 1 c.d.m. Length, about 2*5 c.d.m. Breadth at the constriction, •5 c.d.m. Fresh water. — Manage (P.G.), Rouge-Clo!tre (Del.), Antwerp. Great Britain. N. lepidula Grun.! (H.v.H. Atl., pi. 14, f. 42*; Cahneis lepidula C/.), plate 5, fig. 236. Valve narrowly linear, apices rounded. Central nodule surrounded by a considerable hyaline area. Striae reaching almost to the raphe, parallel, fine, 27 to 30 in r c.d.m. Length, about 2 c.d.m. Breadth, -6 c.d.m. Fresh water. — Groenendael (Delogne). N. perpUSilla Grun. (Ueber neue, etc., i860, p. 552, pi. 2, f. 7 ; H.V.H. Atl., pi. 14, f. 22, 23*), plate 35, fig. 911. Valve minute, oblong, with rounded apices, inflated at the median portion. Transverse striae very delicate, subparallel, indistinct. Length, 1-25 c.d.m. Breadth, '5 c.d.m. Fresh water.— Rouge Cloitre (Delogne), Scotland. Ireland (O'Meara). II. Frustules united in long bands (Diadesmis). * Valve with border furnished with coarse distant beads. N. Gallica (W. Sm.) H. Van Heurck. (H.V.H. Atl., pi. 14, f. 39* ; Type No. 47), plate 5, fig. 237. Valve linear-elliptic or linear, with median portion somewhat inflated, apices obtuse rounded, presenting throughout the length of the margin an appearance of coarse beads. Raphe surrounded by a slight hyaline zone, 230 SCHIZONEMA. somewhat dilated near the central nodule. Stria gently radiate, very fine, distant, about 28 in 1 c.d.m. Frustules with girdle face quadrangular, united into long filaments. Length, -8 to 1*5 c.d.m. Breadth, about '3 c.d.m. Fresh water. — Brussels (Delogne). England, France. ** Valve with margin not furnished with coarse beads. N. Flotowii Grun. ! (H.v.h. Atl., pi. i4, f. 41*; Type No. 48), plate 5, fig. 238. Valve linear, with apices rounded, median portion inflated. Raphe surrounded by a considerable hyaline zone, and much dilated at the median portion. Striae radiate, fine, 35 in 1 c.d.m. Length, 1*5 c.d.m. Freshwater. — Frahan (Del.). N. contenta Grun. ! (H.V.H. Atl., pi. 14, f. 31*, sub. n. N. ttinodis ; Type No. 146), plate 5, fig. 239. Valve linear, inflated at the median portion and at the apices. Raphe surrounded by a considerable hyaline zone, only just a little dilated near the central nodule. Striae very delicate, almost parallel, about 36 in 1 c.d.m. Length 7 to t c.d.m. Breadth, 2 to '025 c.d.m. Humid positions. — In a slate quarry at Rochehaut (Del.) var. biceps. (H.V.H. Atl., pi. 14, f. 31**), plate 5, fig. 240. Differs from the type form by the central inflation, which is very slight or absent. Groenendael (Delogne). Observ. — The group " Minutissimce " is not a natural group. The species included in it ought to be incorporated in the other groups previously mentioned. If all these forms, which have nothing in common but their small size, are allowed to remain grouped, it is only to facilitate comparison and consequently the determination of the different species. B. Naviculse not free. Frustules naviculoid, inclosed in tubes or gelatinous-mucous fronds. Sub-genus II. — Schizonema. Frustules naviculoid, generally feebly silia'ous, enclosed in mucous tubes which simulate the higher algce. Habitat : maritte. I agree with Mr. Grunow that it is preferable to preserve distinct the Naviculce belonging to the old genus Schizonema on account of the character SCHIZONEMA. 231 impressed on the species by the abundant formation of coleoderm. I do not attach any importance to the form of the fronds, and in my classification of species I follow the same order as that employed for other ISiavicula. All the Schizonema can, in my opinion, be reduced to a very small number of type forms, and I only describe those, of whose existence as species there can be no doubt. ANALYSIS OF SPECIES. Costae resolvable. No costae, valve striated. f Valve quite small, being only 1 c.d.rn. in length S. corymbosum. -., , c f Valve large, central nodule surrounded Valve of °._i li- 1 1: several c.d.m. in length. by a considerable hyaline area S. Smitiiii. Valve small, central nodule without any hyaline area . . .8. molle. ' Valves furnished with an obvious pseudo-stauros . S. crucigerum. ( Valve with strong puncta, not forming No pseudo- stauros. longitudinal lines ] Strice fine, with divisions forming longi- l_ tudinal lines S. Grevillei. S. ramosissimurn. I. Radiosse. N. (S.) Smithii C. Agardh. (H.V.H. Atl., pi. 15, f. 33 ; Type No. 154), plate 5, fig. 241. Valve lanceolate, with apices somewhat produced rostrate. Raphe sur- rounded by a very narrow hyaline zone dilated round the central nodule into a rounded area. Stride finely divided transversely, of unequal length round the central nodule ; the median ones radiate, the terminal convergent, about 13 in 1 c.d.m. Length, about 6 c.d.m. Breadth, 1*3 c.d.m. Marine.— Mouth of the Scheldt (V. de Bosch). England, Scotland, Ireland, etc. N. (S.) molle W. Sm. ! (S.B.D., i, p. 77, pi- 58, £ 365; H.V.H. Atl., pi. 15, f. 24*), plate 27, fig. 780. Valve lanceolate, with subacute apices. Striae, about 14 in 1 c.d.m., slightly radiant, reaching to the raphe. Length, 3 to 4 c.d.m. Marine. — North Sea. England (Exmouth ; Coll. W. Sm. ). N. (S.) corymbosum Ag. (Syst., p. uj H.V.H. Atl., pi. 15, f, 21*), plate 27, fig. 780 bis. 232 SCH1Z0NEMA. Valve excessively small, elliptic lanceolate, with apices obtuse rounded. Striae radiant, almost straight, reaching to the raphe, 20 or 21 in 1 c.d.m. Length, 1 c.d.m. Breadth, about 0-25 c.d.m. Marine. — Coasts of Northern Europe. II. Stauroneidese. N. (S.) crucigerum W.Sm. ! (S.B.D., ii., p. 74, pi. 56, f. 354, and pi. 57, f. 356; H.V.H. Atl., pi. 16, f. 1*; Type No. 151), plate 5, fig. 242. Valve lanceolate acute ; central nodule prolonged up to the margins of the valve into a stauros, which is covered with two striae more robust than the others. Striae reaching almost to the raphe, 24 in 1 c.d.m., almost parallel, finely divided transversely, with divisionj simulating delicate longitudinal striae. Length, about 7 to 8 c.d.m. Breadth, about 1 c.d.m. Marine. — Scheldt at Antwerp. Blankenberghe. England, Scotland, Ireland. The photograph has not reproduced the stauros as it is found in the original figure. In the figure in my Synopsis the valve appears without a stauros. III. Perstriatae. N. (S.) Grevillei Agardh. (Consp., p. 19; H.V.H. Atl., pi. 16, f. 2*; Type No. 152), plate 5, fig. 243. Valves rather broadly lanceolate, with obtuse apices ; striae reaching almost to the raphe, strongly punctate transversely, the 3 or 4 median ones straight, very distant, the others approximate, about 20 in 1 c.d.m., gently radiate up to the apex of the valve. Girdle face quadrangular, with rounded apices, com- pressed at the median portion ; connective membrane with numerous longitu- dinal striae. Length, 3 to 7 c.d.m. Breadth, about 1*5 c d.m. Marine. — Ostend (Weslendorp, n. 896 and 897), Blankenberghe. England, France, Denmark, Heligoland. Later researches, after the publication of the Atlas to my Synopsis, has proved that the JS'avicula J)elognei (pi. n, f. 13) ought to be considered as a form of S. Grevillei. N. (S.) ramosissimum C. Agardh. (Consp., p. 22; H.V.H. Atl., pi. 15, f. 4*; Type No. 153), plate 5, fig. 244. DICKTEIA. 233 Valves lanceolate, with apices very slightly produced, subobtuse ; striae about 14 in 1 c.d.m., reaching almost to the raphe, gently radiate, finely divided transversely, with divisions simulating longitudinal striae. Length, about 5 c.d.m. Marine. — Blankenberghe. England, France, Bahusie. var. setaceum Kutz. (S. setaceum Kiitz.), H.V.H. Atl., pi. 15, f. 13*), plate 5, fig. 245. Differs from the preceding by shorter valves, and strice more strongly radiate. Length, about 25 c.d.m. Marine. — Blankenberghe. France, Bahusie. Sub-genus III. — Dickieia. Navicula enclosed in fohciceous fronds. Marine habitat. N. ulvacea (Berk.) H.V.H. {Dickieia ulvacea Berkeley in Kiitz. Baa, p. 119; Sp. Alg., p. 109; H.V.H. Atl., pi. 16, f. 10*), plate 27, fig. 78x- Valves elliptic, with apices obtuse rounded. Raphe surrounded by a very narrow hyaline area, dilated into a false stauros at the median portion ; striae 16 in 1 c.d.m., radiate, robust, finely divided transversely. Length, 8*5 to i2-5 c.d.m. Breadth, 2-5 to 3^5 c.d.m. Frustules scattered in gelatinous leaf-like fronds. Marine. — Aberdeen, Scotland (Dickie!), Ireland (O'M.). N.B.— -The Dickieia pinnata Ralfs and D. Dansci Thw. are not entered here, the first is a Schizonema and the second a Mastogloia. The genus Navicula is very vast, and includes at least 1,000 forms. It is therefore conceived that authors, especially those who have had to describe the forms of the whole world, have endeavoured to simplify these difficulties by arranging forms into a certain number of groups which they have elevated into the rank of genera. Some of these genera have been admitted into the present work, but it is still necessary to make a few remarks about others, and to indicate their characters. They will be found here in alphabetical order. Alloioneis Schumann. (1867). Navicula? rhomboidal in transverse section. Valves showing long striae on one side of the raphe and shortened striae on the other. About half a dozen exotic forms belong to this section. Anomaeoneis Pfitzer. (187 1, Ueber Bau., etc.). This group- corresponds with my group of Sculptcce, 234 LIBELLUS. Caloneis Cleve. (rSor, in Le Diatomiste, i., p. 66). Valve with striae not punctate or indistinctly punctate, and crossed by lines or longitudinal bands. Prof. Cleve includes in this group all the species belonging to my divisions : Abbreviated, Formosa', Limosce, and Lineares. Craticula Grun. (1868, Novara, p. 20). This genus was based on certain anomalous valves showing transverse thickenings in the interior, such as Naviada ambigua Jorma craticula. Mr. Grunow himself has now abandoned this genus. Diadesmis Kiitz. (1844). This genus comprises certain Navicular found united in long bands, such as N. gallica, Fiutowii, and contenta. Diploneis Ehr. (1840), created for Navicular with the valve constricted in the median portion : N. didyma, Bombus, bomboides, etc. This genus has been revised by Prof. Cleve, who, however, bases it on the peculiar form of nodule which is laterally prolonged into robust silicious horns surrounding the raphe. My group of Didyma are included in the genus Diploneis, with the exception of N. Musca. Falcatella Rabh. (1853, Suss.-Diat.) an unaccepted genus and a medley of forms with arcuate valves belonging to different genera : Navicula, Synedra, Nitzschia. Libellus Cleve. (1873, D. of Arctic Sea). Navicula? whose connective membrane is plicate so as to imitate an accumulation of pages in a book. The N. (Schizonemi) Grevillei and TV. Bulnheimii form part of this genus as well as five other British species as follows : — ANALYSIS OF SPECIES. Valve furnished with a pseudo-stauros ' Valve narrowly linear .... Valve very narrowly acute-lanceolate ; very small Valve without a pseudo- stauros. Valve not narrowly linear. form . N. simulans. . N. plicata. N. Bulnlieimii. Valve rather large. Median striae more distant than the others Striae not thus and valve only seen with difficulty in consequence of the length of the sutural zone. . N. (S.) Grevillei. f Frustules simulating an Amphora ; sutu- ral zone with very numerous continu- ous pleats . N. complanata. Sutural zone very broad, with very numerous pleats, apparently interrup- ted in the middle . N. Hyalosira. Valve very convex, distinct ; median striae not more distant ; zone with numerous pleats . . N. rhombica. LIBELLUS. 235 N rhombica Greg. (Q.J.M.S., 1S55, iii., p. 40, pi. 4, f. 16 ; Donk. Brit. Diat., pi. 9, f. 1*), plate 27, fig. 783. Valve rhombic, lanceolate, strongly convex, with apices acuminate, sub- acute. Transverse striae finely punctate, the median ones somewhat radiate, the others sub-parallel, 16 to 16-5 c.d.m. Length, about 7 c.d.m. Breadth, about 1*5 c.d.m. Prof. Cleve considers that this form does not essentially differ from IV. (Schiz.) Grevillei. Marine. — England, Scotland, Ireland, Denmark. N. simulans Donk. (Brit. Diat, p. 60, pi. 9, f. 3*), plate 27, fig. 784. Valve linear, with parallel margins, apices cuneate. Stria; very fine, leaving a stauroneiform blank space. Girdle face with apices truncate, rounded angles, somewhat constricted at the median portion. Length, 6 to 7^5 c.d.m. Breadth, 1-5 c.d.m. Marine. — Xewbiggin, Northumberland (Donkin). We give the above description according to Donkin, but we have not seen any authentic specimens. Donkin and other authors connect with this form Amphiprora conslrida W. Sm. This is an error : the forms from Prof. Smith's herbarium are not those of a Navicula. N. plicata Donk. (Brit. Diat., p. 59, pi. 9, f. 2*), plate 28, fig. 787. Valve narrow, linear, with subcuneate apices. Strice fine, 20 in 1 c.d.m., not reaching quite to the raphe. Girdle face broad, linear, with apices trun- cate, angles rounded, constricted at the median portion with the connecting zone showing numerous pleats. Length, 8 or 9 c.d.m. Breadth of the valve, i'5 c.d.m., and of the girdle face, 3 c.d.m. Marine sands. — Warkuorth, Northumberland (Donkin). N. COmplanata Griin. (Amphora comp!a?iaia Grun. ; Hedwigia, vi., p. 25 ; Ad. Schm. Atl., pi. 26, f. 45*), plate 27, fig. 785. Valve linear lanceolate, acute ; striae 18 or 19 in 1 c.d.m. Length, 3*5 c.d.m. Breadth, o#5 c.d.m. Girdle face rectangular, showing very numerous pleats; breadth, 3-5 c.d.m. Marine. — Finmark, Sweden (H.L. Sm., Type No. 612 !). 236 NKIDIUM. N. Hyalosira Cleve. (in Le Diat, i., p. 77, pi. 12, f. 11*), plate 27. fig. 786. Valve convex, thin, lanceolate, rostrate or with rounded apices ; striae punctate, 29 in 1 c.d.m. Frustule quadrangular, connecting zone with numerous pleats. Length, about 2 c.d.m. Frustule feebly silicious. Marine. — Month of the Tay, Scotland (Cleve and Moller, No. 309 !) Cresswell, Northumber- land, England (Deby.). Neidium Pfitzer. (1S71. Ueber Bau und Entw. d. Baa, p. 39). This very natural group corresponds to my Affines ; it is based on the form of the endochrome, on the apices of the raphe near the central nodule being turned in opposite directions, on the striation of the valve being often oblique, and on this striation being frequently interrupted by one or more longitudinal sulci. Pinnularia Ehr. (1840). Valve furnished with costae and not striae. This genus corresponds to my group Pinnularia. Former authors also included in it the Radiosce, whose striae could not then be resolved into beads. Rhaphidodiscus Th. Christian (1887, in the Journal "The Microscope," p. 67). This genus is, according to Mr. Deby, based on the accidental position of a Navicula in a valve of Melosira. It is also perhaps founded on a disciform Navicula, such as that represented in Fig. 33 at the side. This figure, which corresponds very well with that of Mr. Christian, is drawn from one of my photographs, and reproduces a valve found by Mr. Weissfiog in material from Naparima in the ^. ./ig. 33. jslan(j 0f La Trinite, Antilles. Discnorm Aavicula. Lately, Prof. Brun, having been good enough to lend me the photographs and preparations which he received from Mr. Christian, I have been able to assure myself that the Naparima diatom in no wa> differs from that of Mr. Christian's specimen, which is a genuine Navicula. Mr. Deby's explanation is the only one that satisfactorily explains the figure published by Mr. Christian. We have reproduced this as figure 913 on plate 35. Schizostauron Grun. (1867, in Hedwigea, p. 28). A genus containing eight species, all from the South of Europe, or Extra- European. Round the central nodule is a blank space, stauroneiform (or a true stauros ?), bifurcated into a St. Andrew's cross. Stauroptera Ehr. (1843). Group including all forms possessing a pseudo-stauros. Stictodesmis Grev. (1863), South Pac. Diat., p. 30.). Based on the craticular state of the valve, analogous to Craticula. Fig. 34 represents Stictodesmis Australis Grev., the most common form of this genus. CVCLOPHORA. 237 III *< 1 IF 1 1 1 r I'- It 1 is Wt 1 ll 1 , Fig. 34. — StictoJesmis Australia Grev. The Navicula which has given occasion for the creation of St. Australis appears to be the N. Johnsonii or an allied form. Trachyneis Cleve (in litteris, 1893), a genus which corresponds with our Aspera, and comprises N. aspera and Clepsyara. ? ? Cyclophora Castr, 1878. Frustules with girdle face plicate, showing in girdle view a semi-annulus on the visible part of one valve. Frus- tules in chains. Jl C. tenuis Castr. (Atti. Ace. pont. N. Line, XXXI., and Diat. Chall., 18S6, p. 53). Valve linear, very narrow, somewhat F'g- 35-— Cyclophora n.sp. attenuate near the apices, which are obtuse rounded, bearing a large annulus at the median portion. Raphe delicate, terminated by round nodules somewhat distant from the apices, central nodule indistinctly surrounded by an elliptic annulus. Striae rect- angular, very delicate, the transverse ones about 40 in 1 c.d.m. reaching to the raphe. Girdle face rectangular. Sutural zone with numerous fine pleats, bearing a semi-annulus on the margin of che valve. Length, 4 to 7 c.d.m. Marine. — Ancona, Naples (Castr. !). Philippine Islands. The above figure represents the valve of a Cyclophora in a preparation by Mr. Weissflog, from the Labuan Islands (Vega Expedition), which differs considerably from C. tenuis by its length, median constriction and terminal nodules, which are nearer the apices and by the absence of any central nodule. Subsequent researches ought to show if this is really a new form, which is probably the case. The entire characters of Cyclophora prove this form to belong to the Navicular tribe. Count Castracane has ol late years withdrawn the name of Cyclophora, and given to the above C. tenuis that of Diatoma hyalina jorma Cyclophora, The pleats of the connecting zone and the presence of a true raphe does not allow me to adopt Count Castracane's latest opinion. I do not, however, believe that in the C. tenuis 23* RHOICONEIS. Fig. 36. Rhoiconeis Garckeana Grun. we are dealing with a true genus, but only with a craticular state of a Naviculoid form; however, the species of Mr. Weissflog may belong to another genus. GENUS 8.— RHOICONEIS GRUN., 1863. Valves flexed, each furnished with a coarse central nodule. Frustules flexed with connecting zone very developed, showing striae arranged in longitudinal rows. This interesting genus resembles on first view an Achnanthes, but it differs from it in that each of the two valves is furnished with a nodule. It includes a dozen species, none of which live on our shores. The figure above represents Rh. Garckeana Grun., photographed from an original specimen of Mr. Grunow. GENUS 9.— CYMATONEIS CLEVE, 1894. (In Synopsis of the Naviculoid Diatoms*). Valve divided by longitudinal ridges into two or more divisions. Terminal nodules distant from the apices of the valve. Puncta arranged in longitudinal and transverse rows. This beautiful genus is founded on three forms, which are recognized at first sight, but are all unknown to our shores. C. sulcata (Grev.) (JNav. triundulata Gtun.), lives in the Mediterranean and Tropical Seas. C. quadrisulcata {Grun) {Nav. quadrisulcata Grun.) has been found in St. Paul's Island, and C. circum- vallata Cleve is found in the Balearic Islands, Ceylon, Japan, and Labuan. GENUS 10.-COLLETONEMA (BREB, 1849) H. VAN HEURCK. Valve, with structure slightly eccentric ; terminal nodules considerably distant from the apices of the valves from which they are separated by very radiate striae. Frustules enclosed in tubes. Genus forming the con- necting link between Encyonema and Navicula. Fig. 37-. Cymatoneis circumvallata. F'g- 2,%-—Colleto- netna lacustre. Only one species. VANHEURCKIA. 239 C. lacustre (C. Agardh.) H. Van Heurck. (Schizontma lacuslre C. Agardh! Colletonema subcohizrens Thwaites. — H.V.H. Atl., pi. 15, f. 40* ; Type No. 155), plate 5, fig. 246. Valves lanceolate, gently attenuate, with apices obtuse, sometimes very slightly rostrate, one of the sides of the valve often narrower than the other. Striae robust, finely divided transversely, very radiate at the median portion of the valve, then convergent and becoming again very radiate at the apices, 9 in 1 cd.m.j more distant and shorter or absent round the central nodule. Length, 3 to 6 c.d.m. Fresh water. — England (W. Sm.), Sweden. Not yet found in Belgium. GENUS 11. BREB., 1868, VANHEURCKIA Char. Emend. Frustules naviculoid, free, or very rarely enclosed in single file in a membranous tube. Valves with striae fine, parallel, rarely slightly radiate at the median portion of the valve. Central and terminal nodules linear-elongated between the two branches of a double raphe. Prof. Cleve has re-established the genus Frustulia of Agardh to receive Vanheurckia. This proposal appears untenable. Agardh defined his Frustulia (Syst. Alg., 1824, p. 13) as " Frustula acicularia linearia vel cuneata muco obvoluta in corpus lineare aggregata," and in his Conspectus Crit. Diatomacearum (1830, p. 43) he repeats, " Frustula linearia, libera vel muco amorpho immessa, solitaria vel binatim conjuncta." These definitions say practically nothing at all, and accordingly both he and his successors have accumulated in this genus anomalous forms : F'g- 39- Amphora, Navia/la, Synedra, etc. The genus established by de Vanheurckia . . . . vulgaris. Brebisson on the other hand has very distinct characteristics, and deserves to be preserved, and more justly so than many others that have been admitted in this work. The genus includes 5 or 6 species, of which the most beautiful is V. Lewisiana Breb., which is found in America, India, and Guiana. m Strine quite parallel, raphe continued over all the valve. ANALYSIS OF SPECIES. Valve rhomboidal-lanceolate ; endo- chrome yellowish. . V. rhomboides. Valve lanceolate-elongate ; endochrome greenish. . . .V. viridula. k Median striae slightly radiate ; 1 aphe interrupted near the central nodule V. vulgaris. 240 VANHEURCKIA. I. Stria quite parallel: Eu-Vanheurckia. V. rhomboides Breb. ! (Monog. genus Vanheurckia, p. 204 in An. Soc. Phyt. et Mic. de Belg. j H.V.H. Atl., pi. 17, f. 1 and 2* ; Type No. t6o), plate 5, fig. 249. Valves rhomboidal-lanceolate, attenuate and slightly constricted towards the apices. Raphe double, with threads approximate, continuous. Transverse striae fine, reaching to the raphes, about 28 in 1 c.d.m., finely moniliform ; Endochrome yellowish. Length. 7 to 8 c.d.m. Fresh water, peat bogs.— Calmpthout (Deby) Ard. Lieg. (De Wild.) England, France, etc. var. crassinervis. (N. Crassinervia Breb. /—TV". Saxonica Rab. ; H.V.H. Atl., pi. 17, f. 4 and 5 ; Type No. 162), plate 5, fig 250. Size smaller, about 5 c.d.m. Valve with apices more rostrate; stria; very fine and very difficult to resolve, 34 to 35 in 1 c.d.m. V. viridula Breb. (Soc. cit., p. 203; H.V.H. Atl., pi. 17, f. 3*; Type No. 163), plate 5, fig. 251. Valves rhomboidal-elongated, attenuated with regularity as far as the obtuse apices. Raphe with threads approximate, continuous. Striae fine, 28 to 30 in 1 c.d.m., parallel, finely moniliform. Endochrome greenish, Frustules sometimes enclosed in tubes. Length, 10 to n c.d.m. Fresh water,— Ard. Lieg. (De Wild. ). — France. 77. Median stria slightly radiant : Pseudo-V anheurckia. V. vulgaris (Thwaites) H. Van Heurck. (Coiietonema Vulgare Thw. ; H.V.H. Atl., pi. 17, f. 6*; Type No. 164), plate 5, fig. 252. Valves elliptical-lanceolate, with apices obtuse, slightly contracted-rostrate. Raphe double with narrow threads, then approximate and interrupted near the central nodule which is surrounded by a small hyaline area. Striae fine, delicate, the median striae slightly radiate, the terminal parallel, about 34 in 1 c.d.m. ; the median striae more robust, more distant, 24 in 1 c.d.m. and more radiate. Frustules enclosed in tubes generally without branches. Length, about 5 c.d.m. Breadth, about 1 c.d.m. Fresh water. — Antwerp, Rochehaut (Delogne). Ard. Lieg. (De Wild.) — England, France. STENONEIS. 241 GENUS 12.— STENONEIS CLEVE, 1894. Fig. 40. Stenoneis inconspicua. Valve narrow, with rounded apices. Central and terminal nodules very small, rounded. Raphe indistinct, bordered by two strong ribs or silicious costae. Transverse striae fine. Axial area indistinct. Only one species known, S. inconspicua Greg, (sub Navicula (?) Diat. of Clyde, p. 6, pi. 1, f. 3 ; Cleve Synop., pi. 5, f. 28*), plate 28, fig. 789. Valve linear, frequently gibbous in the median portion, with apices rounded, obtuse ; nodules small, the terminal ones somewhat distant from the apices. Raphe bordered by two strong silicious costae. Striae 26 to 1 c.d.m., perpendicular to the raphe throughout, absent at the median portion where there is a broad hyaline transverse band. Length. 5 c.d.m. Breadth, 75 c.d.m. Marine. — North Sea (Scotland, Greg., Bahusie, Cleve.). y GENUS 13.— CISTULA CLEVE, 1894. Valve rectangular, broad. Central nodule very small. Raphe between two strong silicious costae. Striae radiant, slightly inter- rupted by several hyaline bands. Only one species known. longitudinal Fig. 41. — Cistula Lorenziana, C. Lorenziana Grun. (sub Navicula in Verh., i860, p. 547, pi. 3, f. 3* ; Cleve Syn., pi. 1, f. 31), plate 28, fig. 790. Valve rectangular, sometimes somewhat gibbous in the middle and at the apices. Striae gently radiant, about 17 in 1 c.d.m., composed of elongated R 242 AMPHIPLEURA. dots, arranged in regular longitudinal rows, 12 in 1 c.d.m., flexed in the middle. Length, 4-5 c.d.m. Breadth, 2 c.d.m. Marine. — South Coast of England (Roper.). GENUS 14.— AMPHIPLEURA KUTZ., 1844. Frustules fusiform. Valves narrowly lanceolate, furnished near each edge with a marginal keel. Central nodule obsolete ; the two terminal nodules very elongate. The genus Amphiplcura has for a long time been noted as a microscopical test of extreme difficulty, and, until the invention of homogenous objectives, the trans- verse striae could not be seen without the assistance of some extraordinary objectives, such as the i-6th of Tolles, and then it was necessary to employ monochromatic illu- mination. It was only in 1884, by employing a prepara- tion of silvered Amphipkura, that I was able to resolve and photograph this diatom under a silvered aspect. Fig. 42. — Amphiplcura . ,. , , fellucida. This resolution was for a long time disputed, and as other microscopists were unable to obtain the same resolution, it was thought that I was the victim of an optical illusion. The discovery of the arsenical medium, the 2-4 of Prof. Smith, and especially the construction of the famous objective with an aperture of r6o, which Messrs. Zeiss placed at my disposal in 1889, enabled me in that year to publish an irreproachable photograph of the Amphipkura resolved into beads, and that put an end to all further dis- cussion on the subject. The genus Amphipkura includes four or five well-established species, only one of which, and that the most delicate, lives in our regions. The Amphi- pkura Lindheimeri, the most beautiful and largest species, inhabits America, but a variety M Lindheimeri var. Truanii H.V.H.), has been found in Spain. A. pellucida KiitZ. (Bac, p. 103, pi. 3, f. 52, and pi. 30, f. 84 ; H.V.H. Atl., pi. 17, f. 14, 15 and A*; Type No. 165), plate 5, fig. 253. Valve narrowly lanceolate, with acute apices. Raphe not interrupted in the median portion of the valve. Central nodule very rudimentary ; REICHELTIA. 243 terminal nodule very elongated. Transverse strise only visible with great difficulty, 37 in 1 c.d.m. on an average. Length, 8 to 14 c.d.m. Fresh water. — Antwerp, Louvain, Brussels. — Sussex (W. Sm.). Norfolk (Kitton). Hull (Norman). Ireland (O'Meara). Scotland (H.L. Sm., Type No. 7). GENUS 15.— REICHELTIA H.V.H., 1895, *n Litt. Valve lanceolate, slightly gompho- nemoid simulating an A mphi pleura. Girdle face cuneate. A single species, R. nobilis {Reichelt) H.V.H., found in a fossil state at Hainspach. Fig. 43- Reicheltia nobilis. This new genus is excessively interesting, and we do not know of any analogous one. The valve displays rather delicate transverse costae, separated at the median portion by an elongated hyaline space, simulating the terminal nodules of the Amphipleura, but in these hyaline spaces there is a delicate bifurcated raphe, like that of the large Binnularia, and terminating at the apex in a nodule, while the other end of the raphe, after having traversed a kind of nodule placed in a small depression is prolonged a little further on. Between the costae is a double row of very delicate beads, about 20 in 1 c.d.m. About 7*5 costal in 1 c.d.m. Length of valve, about 9 c.d.m. Breadth at the median portion, about 1 c.d.m. The figures in the text are from one of my photographs, that of the valve x 600 diameters, and the details of structure x 1000 diameters. This very curious form has the combined characteristics of an Amphipleura, Berkeley a, and Gomphonema. I have been able thoroughly to study it, thanks to the numerous examples which Mr. H. Reichelt has had the kindness to place at my disposal. The photographs have been made with Zeiss objective of i"6o N.A. The examination made with this objective has enabled me to ascertain that the description given by Mr. Reichelt by means of objectives of less resolving power was defective, and did not correspond with the very curious structure of the valves. I have, therefore, with the assent of Mr. Reichelt. ventured to change the name given by its author, and I have great pleasure in dedicating to him this interesting genus. !44 BREBISSONIA. GENUS 16.— BREBISSONIA GRUN., i860. Valve with central nodule linear, very elongate ; terminal nodules distant from apices. Frustules pediculate. Brebissonia Boeckii (Kutz.) Grun. (i860, Wien, p. 512 ; Doryphora Boeckii, IV. Sm., S.B.D. i., p. 77, pi. 24, f. 223; H.V.H., Type No. 150)- Fig. 44. — Brebissonia Boeckii. GENUS 17. Valve lanceolate, rhomboidal, with striae very robust, radiate, 10 in 1 c.d.m., finely divided transversely like those of the Radiosce (Navicula). Raphe surrounded by a considerable hyaline area, often narrowed near the central nodule, slightly extended beyond the terminal nodules. Length, 7 to 13 c.d.m. Breadth at the median portion, 2 c.d.m. Marine. England (W. Sm., Kitton, Norman); Dundee, Scot- land (Kitton in Baxter's Coll., No. 3463); Ireland (O'M.); Kiel, Germany (Eulenstein) ; North Sea, near Christiania (D. Boeck). ROUXIA J, BRUN AND F. HERIBAUD, 1893. Valve elongated, linear, with central nodule rudimentary or absent, terminal nodules very elongated, and narrow at the apices. A row of beads round the nodules and the raphe, which is not distinct. Frustule A single exotic species. girdle view sigmoid. Fig. 45. — Rouxia Per agaili. Rouxia Peragalli J. Brun and F. Herib. (Diat. d'Auvergne, p. 156, pi. 1, f. 12). From Japan. The authors of the genus place it among the Pseudo-raphidieae, but as it appears to me to have a greater affinity to the Amphiphura, Berkdeya etc., I prefer to arrange it near those genera. BERKELEYA. 245 GENUS 18.— BERKELEYA (GREV. 1827), H. VAN HEURCK, Emend. Valves with central nodule sub-divided, divisions more or less separated. Raphe absent between the divisions of the nodule. Frustules naviculoid, enclosed in mucous tubes as in the Schizonema. ANALYSIS OF SPECIES. f r ('About 32 strife in i c.d.m. B. fragilis. Valves sublinear, narrow ; strire quite parallel \ ( About 26strire in 1 c.d. m. B. micans. . Valves elliptical-lanceolate, median strire parallel, terminal radiate . . B. Dillwynii. OT s I B. fragilis Grev. (Scot. Crypt. Flor. pi. 294 ; H.V.H. Atl., pi. 16, f. 12). Valves linear, narrow, and very elongated ; sub- divisions of central nodule rather approximate ; striae quite parallel, delicate, 32 to 40 in 1 c.d.m. Length, about 8 c.d.m. Breadth, about 0-4 c.d.m. Marine. — Not yet discovered in Belgium. England (Mrs. Griffiths). Scotland (Grev., Arnott), Eulen, Type No. 80. Ireland (O'Meara). France, Brest (Coronan) ; Cherbourg (Bre'bisson). Prof. Cleve makes B. fragilis only a variety of the following : — B. micans (Lyng.) H.V.H. (H.V.H. Atl., pi. 16, f. n* ; Type No. 156), plate 5, fig. 254. Valves linear, narrow and very elongated ; sub- divisions of central nodule rather distant ; striae parallel, delicate, 26 in 1 c.d.m. Length, 8 to 9 c.d.m. Breadth, 0-4 c.d.m. Marine. — Not yet discovered in Belgium, but found in France, Holland and Denmark. Fig 45 B. Dillwynii (Agardh) H.V.H. (H.V.H. Berkeleya fragilis. Atl., pi. 1 6, f. 1 5* J Type No. 157), plate 5, fig. 255, Valves elliptical lanceolate, narrow, with divisions of central nodule more or less distant. Median striae parallel, terminal radiate, delicate, 30 in 1 c.d.m. Length, 1*5 to 3-5 c.d.m. Breadth, C4 to o-6 of c.d.m. Marine. — Ostend (West. 895 sub. Schizonema rutilans). Ostend leg. (Grunow). England (Kitton), Scotland (Eulen, Type No. 81, 82). 246 SCOLIOPLEURA. GENUS 19.— SCOLIOPLEURA GRUN, i860. Frustules free, with valves naviculoid, very convex, slightly twisted spirally so as to render the raphe and connecting zone more or less obliquely-sigmoid. ANALYSIS OF SPECIES. Valve with robust costne, between which are two rows of fine granules . S. latestriata. Valve with striae distinctly moniliform, about 10 in i c.d.m. ; raphe strongly sigmoid . . . . . . S. tumida. [ Striae difficult to resolve into beads, 15 in 1 c.d.m. ; raphe scarcely sigmoid S. Westii. S. latestriata (Breb.) Grun. ! {Amphiprora latestriata Breb. ; Scoliopleura cowvexa Grun.; H.V.H., pi. 17, f. 12*; Type No. 202), plate 5, fig. 247. Valve linear, narrow, with cuneate apices. Raphe surrounded by a rather considerable hyaline zone, slightly dilated round the central nodule. Costae robust, about 7 in 1 c.d.m., interrupted near the raphe by a furrow parallel to the hyaline zone. Between the costae are two rows of granules delicate, alternate, seen with difficulty. Length, about 10 to 15 c.d.m. Breadth, 2^5 c.d.m. Kitton), Ireland (O'Meara), Marine. — Ostend (Deby), Englant France, Bahusie (Sweden). Fig. 47. — Scoliopleura tumida. S. tumida (Breb) Rabenh. (Fi. Eur. Alg., p. 229- H.V.H. Atl, pi. 17, f. 11, 13*; Type No. 201), plate 5, fig. 248. Valve lanceolate, very gently attenuate, with sub- acute apices. Raphe surrounded by a small hyaline zone, considerably dilated at the median portion. Striae about 10 in 1 c.d.m. ; those in the centre often unequal in length, radiate, bent, finely punctate. Length, 10 to 16 c.d.m. Marine. — Antwerp (Scheldt), Ostend, Blankenberghe. Common : England (Kitton), France, Denmark. S. Westii (W. Sm.) Grun. (in Wien Verh., i860, p. 555; n. Weslii IV. Sm., S.B.D., i., pi. 16, f. 135*), plate 28, fig. 791. TOXONIDEA. 247 Valve elliptical-lanceolate, with sub-acute apices ; raphe scarcely sigmoid, surrounded by a small hyaline area, scarcely dilated round the central nodule. Stria; fine, about 15 in c.d.m., difficult to resolve into beads ; connecting zone scarcely oblique-twisted. Length, 8 to 10 c.d.m. Marine.— Scheldt (H.V.H.) England (W. Sm. ! Kttton). Ireland (O'Meara). France (Brebisson). Denmark, Holland (Van den Bosch). Note, — Prof. Cleve forms S. latestriata into a new genus which he calls Scoliotropis Cieve, while the two others remain in the genus Navicula. GENUS 20.— TOXONIDEA DONKIN, 1858. Valves elongate, convex, with asymmetrical margins ; striae decussate. Raphe arcuate with its convexity turned towards the convex margin of the valve. Frustules free. ANALYSIS OF SPECIES. Ventral margin straight, dorsal margin very arcuate, valve short thick set T. insignis . Ventral and dorsal margins feebly curved in opposite directions, valve long, elongate . T. Gregoriana. 1 { Fig. 48. Toxonidea insignis. T. insignis Donkin (T.M.S., 1S58, vi., p. 21, pi. 3, f. 2 ; H.V.H. Atl., pi. 17, f. 10* ; Type No. 168), plate 5, fig. 256. Valve with dorsal margin strongly convex, ventral margin straight, apices strongly produced- rostrate on the dorsal side. Raphe strongly arcuate, dividing the valve into very unequal portions. Striae decussate, reaching to the raphe, 22 in 1 c.d.m. Length, about 10 c.d.m. Breadth, about 3 c.d.m. Marine. — Washings of mussels (Debv) Blankenberghe. England (Kitton, Norman, Comber). Scotland (Baxter, Coll., 1794). Ireland (O'Meara), and on all the coasts of the North Sea. T. Gregoriana Donk. (T.M.S., 1858, vi., p. 19, pi. 3, f. 1 ; Per., pi. 9, f. 16*), plate 28, fig. 792. Valve very elongated, with apices produced-rostnte, margins slightly flexed in opposite directions ; ventral margin nearly straight. Raphe dividing the valve into two almost equal portion:. Striae decussate, reaching to the raphe, the oblique 19 and the transverse 20 in 1 c.d.m. Length, 22 to 26 c.d.m. Breadth, about 5 c.d.m. Marine. — Blankenberghe (H.V.H.). England (Kitton, Comber). Ireland (O'Meara), and found, but in small quantities, on all the coasts of the North Sea. 248 DONKINIA. GENUS 21.— DONKINIA RALFS, i860. Valve carinated, with keel sigmoid, inter- rupted at the median portion by the central nodule. Keel not accompanied laterally by projecting lines (or alae). Frustule strongly constricted at the median portion. ANALYSIS OF SPECIES. Fig. 49. — Donkinia recta. r Strise rectangular, the transverse 20, the longitudinal 21 in 1 c.d.m. \ Striae decussate, fine, 21-24 m l c.d.m. D. recta. D. carinata. D. recta (Donkin) Grun. (Pleurosigma rectum Donk., T.M.S., 1858, vi., p. 23, pi. 3, f. 6 ; H.V.H. Ad., pi. 17, f. 9*; Type No. 194), plate 5, fig. 286. Valve broadly linear, with apices attenuate, subcuneiform-acute. Raphe strongly sigmoid. Strise reaching to the raphe, rectangular, about 2 1 in 1 c.d.m. Girdle face strongly constricted at median portion. Length, about 8 or 9 c.d.m. Marine.— Washings of mussels. England, Ireland (O'Meara). Rather common on all the coasts of the North Sea. var. angusta H.P. {Pleurosigma angustum Donk.). Narrower, with keel more eccentric. England, Ireland (O'Meara). var. minuta H.P. (Pleurosigma minuta Donk.). Small form of type. Length, about 6 c.d.m. Rather common. — Ireland (O'Meara). D. carinata (Donk.) Ralfs (Ralfs in Prit. Inf., p. 921, pi. 8, f. 49*), plate 35, fig. 912. Valve straight, linear-lanceolate, with apices acute, very convex. Raphe very strongly sigmoid. Striae decussate, fine, 21 to 24 in 1 c.d.m, Length, 12 c.d.m. Marine, — England, Ireland (O'Meara). PLEUROSIGMA. 249 I ; 1 ; ■m GENUS 22.— PLEUROSIGMA W. Sm, 1853. Frustules naviculoid, elongated, with valves convex, more or less sigmoid. Raphe more or less sigmoid. Striae decussate or rectangular, reaching almost to the raphe. Frustules with connecting zone straight, generally free, rarely enclosed in mucous tubes. The endochrome oi-Pleurosigma presents a peculiar arrangement, to which we have already referred in the introduction (,L The genus Pleurosigma includes numerous forms which inhabit all parts of the world. Prof. Cleve divides it into two genera, reserving the name Pleuro sigma for forms with decussating striae, and giving that ot Gyrosigma to those with rectangular striae. The name Gyrosigma is the older of the two, having been given by Dr. Hassall. The special study which Professor Wm. Smith made of the group has caused this name of Pleurosigma to be preserved in spite of the incontestibly prior right of Hassall. An excellent monograph of the genus Pleurosigma, by Mr. H. Peragallo has recently been published in " Le Diatomiste." This work includes the genera Pleurosigma, Toxonidea, Donkinia, and Rhoicosigma, and forms a quarto volume of 35 pages, including 10 plates, containing 271 figures. This monograph is indispensable to anyone who wishes to make an exhaustive study of this difficult group, or to determine exotic species. Fig. 50 Pleurosigma Baltic am. See page 4. ANALYSIS OF SPECIES. Striae decussate (cutting one another obliquely in three directions). All the strias almost equally delicate. Oblique striae ci ossing one another at an angle of about 60°. Central nodule not Median elongated oblique trans- strife versely, not oblique flexed. striae equally distant throughout \/r<±A;„r* C Raphe and valve considerably sigmoid . . .PI. angulatum. Raphe and valve scarcely sig- moid, valve broad, apices obtuse Raphe and valve scarcely sig- moid, valve very narrow, ^ apices acute Median oblique striae, flexed . PI. rigidum. » r, . PI. intermedium. . PI. afflne. Striae rectangu- lar (longi- tudinal and transverse striae cutting one another at right angles). Central nodule elongated transversely ; median oblique striae more distant than the terminal . Oblique ( Raphe straight, abruptly curved at apices striae ' Valve with obtuse apices crossing one another - at an angle of more L than 6o°. Raphe very sigmoid. , - Valve with very acute apices Valve with attenuated apices Raphe with a double flexion Transverse striae delicate, oblique striae robust. I Valve very large, linear-lanceolate, with sub-obtuse apices Valve rather large, very narrowly lanceolate, with acute apices PI. naviculaceum. PI. speciosum. PI. elongatum. PI. acutum. PI. naviculaceum. PI. marinum. PI. formosum. PI. decorum. Frustules not enclosed in mucous tubes. f In brackish water : Valve short, lanceolate, apices broad, longitudinal striae 10-11 in 1 c.d.m. . PI. Hippocampu3. Longitudinal strias further apart and conse- j Marine : Valve short, apices narrow, 7-9 longitu- quently more dinal striae in 1 c.d.m. ' e Fresh water : Valve elongated, narrowly lanceo- late, 10-11 longitudinal striae Marine : Valve linear, very elongated visible than the transverse. Longitudinal and transverse striae equally distant. PI. littorale. PI. altenuatum. . PI. Balticum. Fresh water : Valves lanceolate-sigmoid PI. acuminatum. Longitudinal striae more approximate and - less visible than the transverse. ' Valve very large, transverse striae Apices not rostrate produced. . PI strigilis. narrow . PI. Spencerii. Apices rostrate produced. very distant, robust 1 Valve linear - lanceolate, (more than 1 c.d.m. ) I Valve linear, excessively narrow (less ^ than 1 c. d. m. ) . .PI. tenuissimum. Fresh water : Valve broadly lanceo- late, rostrum rather broad . PI. Parkeri. Marine : Rostrum broad and short, striae very fine . . PI. distortum. Valve linear-lanceolate ; Marine. Rostrum very apices very rostrate . PI. Fasciola. Valve very linear-lanceo- late ; apices extremely rostrate Rostrum apices PI. macrum. inflated at PI. reversum. f Valve very obtuse ; raphe appearing strongly sigmoid . PI. exiruium. Frustules enclosed in mucous tubes, valves short, stubby , Valve obtuse ; raphe appearing gently sigmoid . PI. scalproides, PLEUROSIGMA. 25 1 /. Strice decussate (cutting one another in three directions). A. All striae almost equally delicate. * OBLIQUE STRLE CROSSING ONE ANOTHER IN THE MIDDLE OF THE VALVE AT AN ANGLE OF ABOUT 6o°. PI. angulatum W. Sm. (S.B.D., i., p. 65, pi. 21, f. 205; H.V.H. Atl., pi. 18, f. 2, 3, 4* ; Type No. 169), plate 6, fig. 257. Valve broadly lanceolate, gently flexed, sigmoid, with median part slightly angular. Raphe feebly sigmoid. Striae decussate, having the same direction throughout the surface of the valve, 18 to 20 in 1 c.d.m., the transverse striae slightly more approximate than the others. Length, about 15 c.d.m. Marine. — Common. Antwerp (Scheldt), Blankenberghe, Ostend ; Norfolk (Kitton). This species and its varieties are found on all the coasts of the North Sea. var. ^stuarii. {PL Mstuarii IV. Sm. /; H.V.H. Atl., pi. 18, f. 8* ; Type No. 172), plate 6, fig. 258. Differs from the preceding, with which it is often mixed, by its rather smaller size, and its slightly rostrate-produced apices. var. quadratum. {PL quadratum IV. Sm. / ; H.V.H. Atl., pi. 18, f. 1*; Type No. 171), plate 6, fig. 259. Differs from the type form by its larger size, and its more quadrangular shape. var. major. (H.V.H. Atl., pi. 18, f. 5*), plate 6, fig. 260. Differs from the type form by its much larger size, reaching 22 c.d.m. Blankenberghe. var. delicatulum. {PI. delicatiilum IV. Sm. ! ; in H.V.H.'s Types No. 74 and 172). Valve very narrow and infinitesimally attenuate. Striae 24 or 25 in 1 c.d.m. Length, 16 to 18 c.d.m. Breadth, about 2 c.d.m. Blankenberghe. — Rare. var. strigosum. {PL strigosum W. Sm. /; H.V.H. Atl., pi. 19, f. 2* ; Type No. 170), plate 6, fig. 261. Of very considerable size (more than 30 c.d.m.) with margins infinitesimally sigmoid, not angular, with apices sub-obtuse. This form has not been found in Belgium. — Norfolk (Kitton), Coast of Sussex (W. Sm.), Cheshire (Comber), Humber (Norman), Ireland (O'Meara). PI. rigidum W. Sm. (S.B.D., i., p. 64, pi. 20, f. 198 ; H.V.H. Atl, pi. 19, f. 3* ; Type No. 178), plate 6, fig. 265. Valve almost straight, with apices obtuse, sometimes slightly inflated. Raphe robust, straight, with apices just a little flexed, often with a lateral row 252 PLEUROSIGMA. of points sometimes crossing the central nodule, which is large, rounded. Terminal nodules conical, meeting the margins; striae oblique, 17 to 21 in 1 c.d.m. ; the transverse striae more distant, 16-19 in 1 c.d.m. Marine and sometimes brackish water. — On all our coasts. PI. affine Grun. ! (H.V.H.,pl. iS, f. 9* ; Type No. 175), plate 6, fig. 263. Valve lanceolate, without outline infinitesimally flexed, scarcely sigmoid, with apices sub-obtuse. Raphe feebly sigmoid. Striae iS to 20 in 1 c.d.m., the median striae crossing one another at right angles in the form of slightly flexuous lines, the terminal crossing at an acute angle. Length, 10 to 22 c.d.m. Marine. — Rather rare. Washings of mussels (Deby-), Blankenberghe. England (Kitton). Denmark. var. Nicobarica. (PL Nicobaricum Grun., Novara ; H.V.H. Atl. Supp., f. 34), plate 6, fig. 264. Distinguished from the preceding by a completely straight raphe, and its sides not sigmoid. Marine. — Ostend (according to Kitton). Blankenberghe (observed very frequently in a gathering from the mud of the second basin made in April, 1884). Mr. Kitton believes that PL affine and its var. JSicobarica are forms of Pi. rigidum IV. Sm. ; I, however, think that the flexuous direction so characteristic of the median striae allows me to make a special type of PL affine. var. Normanni. (PI. Normanni Raljs). Distinguished from the type form by its more lanceolate shape (more acute) and its rather finer striae. England (Kitton, Norman). Ireland (O'Meara). PI. navicillaceum Breb. (Diat. Cherb., p. 17, f. 7; PL trans- versalc W. Sm. ; H.V.H. Atl. Supp., f. 35* ; in Type No. 320), plate 6, fig. 266. Valve lanceolate, with symmetrical margins, apices sometimes very slightly turned in contrary directions. Raphe very flexed with strongly eccentric apices. Central nodule very dilated transversely. Transverse striae 18 or 19 in 1 c.d.m. ; median oblique striae slightly flexuous, 13 or 14 in r c.d.m. ; terminal oblique striae 16 or 17 in i c.d.m. Length, 8 to 12 c.d.m. Marine. — Blankenberghe. Rare. England, France, Holland, Bahusie, Denmark. The PL lanceoldtum Donk. approximates closely to the shape of PL naviculaceum, but differs from it in its striation. The transverse striae number 20-21, and the oblique 19 in the middle of the valve and 20-21 in 1 c.d.m. at the apices. PLEUROSIGMA. 253 PI. intermedium W. Sm. (S.B.D., L, p. 64, pi. 21, f. 200; H.V.H. Atl., p. 18, f. 6*; Type No. 174), plate 6, fig. 267. Valve lanceolate, narrow, with margins almost straight ; raphe scarcely sigmoid. Transverse stria? 21 to 23, oblique strice 20 to 22 in 1 c.d.m. Length, 15 to 30 c.d.m. Mr. Grunow remarks that the short are more distinctly sigmoid than the longer specimens. Marine. — This species has not yet been found in Belgium, but has been frequently so in England, France and Holland. It approaches PL delicatulum, and may also be considered as a form of PI. angulatum. var. Nubecula. (PI. Nubecula W. Sin.) Only differs from the type form by its smaller size and more obtuse apices ; the striation is identical. * * STRIDE OBLIQUE, CUTTING ONE ANOTHER AT AN ANGLE OF MORE THAN 6o°. PI. Speciosum W. Sm. (Ann. N.H., 1852, p. 5, pi. i, f. 5 ; S.B.D., i., p. 63, pi. 20, f. 197 ; Perag., pi. 2, f. 16*; H.V.H. in Type No. 170), plate 28, fig. 793. Valve linear-lanceolate, with apices slightly curved, rounded. Raphe straight, parallel to margins, being abruptly bent quite close to the apices. Transverse striae 19-20, oblique striae 16-18 in 1 c.d.m. Length, 21 to 39 c.d.m. Breadth, 2 '5 c.d.m. Marine. — England (W. Sm.). Ireland (O'Meara), and probably also other countries. PI. elongatum W. Sm. (Ann. N.H., 1852, p. 6, pi. 1, f. 4; S.B.D., i., p. 64, pi. 20, f. 199; H.V.H. Atl., pi. 18, f. 7*; Type No. 173), plate 6, fig. 262. Valve very long and very narrowly lanceolate, with striae crossing one another at an angle of about 68°. Length, 21 to 38 c.d.m. Breadth, about 3 c.d.m. Antwerp (Scheldt, where it is rather frequent). Blankenberghc. England (Comber, Norman, Kitton, Stolt.). Ireland (O'Meara) and probably on all the coasts of the North Sea. In my Synopsis I referred this form to the angulatum with which it is closely connected. 254 PLEUROSIGMA. PI. acutum Norm. (Prit. Inf., p. 920 ; Per., pi. 3, f. 1, 4*), plate 35. figs- 914, 9i5- Valve elongate, rather broadly lanceolate, very sigmoid, with very acute apices. Raphe much flexed with eccentric apices. Striae 20-21 in 1 c.d.m. Length, 16 to 18 c.d.m. Marine. — England (Norman). PI. marinum Donk. /T.M.S., 1858, vi., p. 22, pi. 3, f. 3 ; Perag., pl. 3, f. 11*), plate 28, fig. 794. Valve narrow-lanceolate, not sigmoid, with apises slightly tapering rostrate. Raphe having a double flexure in contrary directions between the central nodule and the apices. Oblique striae 20 to 21-5, transverse 21*5 to 22 in 1 c.d.m. Length, 12 to 15 c.d.m. Marine. — England (Donkin, Kitton, Comber, Stolt). Ireland (O'Meara). Cherbourg, France (Brebisson). AA. Transverse striae delicate, oblique striae robust ; raphe strongly sigmoid. PI. formosum W. Sm. ! (S.B.D., i., p. 63, pl. 20, f. 195; H.V.H. Atl, pl. 19, f. 4* ; Type No. 177), plate 6, fig. 268. Valve linear-lanceolate, strongly sigmoid, with obtuse apices. Raphe strongly sigmoid, dividing the apices of the valve into two very unequal portions. Transverse striae rather delicate, 14 to 17 in 1 c.d.m. Oblique striae very robust, cutting one another at right angles, 10 to 12 in 1 c.d.m. Length very variable, but usually from 35 to 45 c.d.m. Marine. — Found in fragments in the washings of mussels, Belgium. England, Ireland, France, and piobably on all our coasts. Pl. obscurum W. Sm. (S.B.D., i., p. 65, pl. 20, f. 206*), plate 28, fig. 795. Is distinguished from the preceding, of which it appears to be a miniature form, by its fine striae, 21 to 25 (according to W. Sm.), and by its very small size, which only reaches from 8*5 to 15 c.d.m. Marine. — England. Pl. decorum W. Sm. ! (Loc. cit., p. 63, pl. 20. f. 196; h.v.h. Atl., pl. 19, f. 1*), plate 6, fig. 269. Valve very narrowly lanceolate, strongly sigmoid, with acute apices. Raphe very strongly sigmoid, dividing the apices of the valves into two very unequal PLEUROSIGMA. 255 portions. Transverse stria? delicate, about 18 in i c.d.m. ; oblique striae robust, 13 or 14 in 1 c.d.m., cutting one another at nearly a right angle. Length, about 25 to 30 c.d.m. Marine — Washings of mussels ; more frequent than the preceding, of which, according to Mr. Kitton, it is only a variety. Same localities. II. Stria rectangular, cutting one another in only two directions ; stria longitudinal and transverse. * Frustules not enclosed in a gelatinous tube. a. LONGITUDINAL STRIDE MORE DISTANT (AND CONSEQUENTLY MORE DISTINCT) THAN THE TRANSVERSE STRLE. PI. Hippocampus W. Sm. (S.B.D., i., p. 68, pi. 22, f. 215; H.V.H. Atl., pi. 20, f. 3*; Type No. 179), plate 7, fig. 270. Valve short, rather broadly lanceolrte, with apices obtuse, abruptly sigmoid ; longitudinal striae, 10 or n in i c.d.m., transverse striae, 15 or 16 in 1 c.d.m., median striae slightly radiate. Length, 13 to 16 c.d.m. Brackish water. — Antwerp (Scheldt), Blankenberghe. England (Kitton, Comber, Norm., Stolt.). Ireland (OMeara). On all our coasts. PI. attenuatum W. Sm. (S.B.D., i., p. 68, pi. 22, f. 216 ; H.V.H. Atl., pi. 21, f. 11* ; Type No. 182), plate 7, fig. 271. Only differs from the preceding by its form being slightly thinner (Grunow) and its fresh water habitat. Length, 19 to 25 c.d.m. Fresh water. — Common and general. Prof. Cleve unites PI. attenuatum IV. Sm. with PI. Hippocampus IV. Sm. var. scalprum (Gaill.) Grun. (Arct. D., p. 55 ; PI. acuminatum Sm. nun Grun. ; H.V.H. Atl., pi. 20, f. 4*), plate 7, fig. 285. Slightly broader and not quite so long in proportion as the preceding, and the striae a little finer. Longitudinal 14 or 15, and transverse striae 17 or 18 in 1 c.d.m. PI. littorale W. Sm. (Ann. N.H., 1852, p. 10, pi. 2, f. 8 ; S.B.D., i., p. 67, pi. 22, f. 214*), plate 28, fig. 796. Smaller and broader at the median portion, but nevertheless quite distinct, in consequence of the longitudinal striae being very robust and distant, 7 to 9 in 1 c.d.m ; transverse striae, 15*5 to 17 in 1 c.d.m Marine. — Coasts of England and France. 256 PLEUROSIGMA. aa. LONGITUDINAL AND TRANSVERSE STRLE EQUALLY DISTANT. PI. Balticum W. Sm. (S.B.D., i., p. 66, pi. 22, f. 207, pi. 23, f. 207, Front, p. 207 ; H.V.H. Atl., pi. 20, f. 1 ; Type No. 180), plate 7, fig. 272. Valve attenuate-linear, with apices obtuse-sigmoid. Raphe sometimes a little more and at others a little less sigmoid. Longitudinal and transverse striae equally distant (sometimes the transverse not quite so close as the longi- tudinal), about 15 in 1 c.d.m. Length, very variable, 21 to 36 c.d.m. Marine. — Common. Blankenberghe, Ostend, Antwerp (Scheldt), and everywhere. var. Brebissonii (PI. Scalprum Brcb. ; H.V.H. Atl., pi. 21, f. 6*; Types Nos. 188 and 189), plate 7, fig. 273. Much smaller and more delicate than the type form, slightly more sigmoid, with a raphe dividing the valve symmetrically throughout its length. Striae about 22 or 23 in 1 c.d.m. Length, 8 to 10 c.d.m. Marine. — Ostend, Blankenberghe (basin), mixed with the type form and abundant. Antwerp (Scheldt), Liverpool (Stolt.), Yorkshire (Norman), Sussex (W. Sm.). Prof. Cleve unites var. Brebissonii with P. acuminatum. var. Wansbeckii {PL Wansbeckii Donk ; PL Balticum, var. /■$ IV. Sm.). Smaller and more acute than the type form, to which it is united by all possible variations, though much smaller; more finely striated, 19 or 20 striae in 1 c.d.m. (H. Paragallo). Marine. — Mixed with type form. PI. acuminatum (Kutz.) Grun. ! nee W. Sm. (Neue o. ung. gek. Alg., i860, p. 561, pi. 4, f. 6 ; PL lacustre IV. Sm. ; H.V.H. Atl., pi. 21, f. 12* ; Type No. 181), plate 7, fig. 274. Valve acute-lanceolate, conspicuously sigmoid. Longitudinal and trans- verse striae 17 or 18 in 1 c.d.m. Dry valve yellowish. Length, 13 to 17 c.d.m. Fresh water. — Common. PI. reversum Greg. (Diat. of Clyde, p. 58, pi. 6, f. 105), plate 28, fig. 797. This is a very doubtful species. Only two examples have been seen by Gregory, and no one else has ever seen an example. The valve is inflated at the median portion and at the apices. aaa. LONGITUDINAL STRL« MORE APPROXIMATE THAN THE TRANSVERSE. a. J'alves with apices not rostrate produced. PI. strigilis W. Sm. (S.B.D., i., p. 61, pi. 22, f. 208; H.V.H. Atl., pi. 20, f. 2* ; Type No. 176), plate 7, fig. 275. a PLEUROSIGMA. 257 Valve very large, narrow, elongate, moderately sigmoid, with sub-acute apices. Raphe slightly flexuous; transverse striae, 13 to 15, longitudinal striae, 16 or 17 in 1 c.d.m. Length, 21 to 50 c.d.m. Marine and brackish water. — Scheldt (H.V.H. ) Coasts of England, Ireland. Denmark and probably all the Coasts of the North Sea PI. Spencerii W. Sm. (S.B.I)., partim.) Valve narrow, linear-lanceolate or lanceolate with apices more or less sigmoid, obtuse or sub-acute. Transverse stria?, 18 to 22, longitudinal striae, 20 to 25 in 1 c.d.m. Length, 8 to 13 c.d.m. Fresh water or slightly brackish water. — The type form and its varieties are met with every- where. Constitutes a vast group of rather different forms, but which are united together by all the intermediate forms ; the following forms may be distinguished as varieties : — var. Smithii Grun. ! {Pi. Spencerii IV. Sm. in S.B.D., i.. p. 68, pi. 22, f. 218: H.V.H. Atl., pi. 2t, f. 15*; Type No. 186), plate 7, fig. 276. Valves lanceolate-sigmoid. Central nodule small, elongate. Transverse striae 18*5, longitudinal striae 21 '5 in 1 c.d.m. Length, 8 to 9 c.d.m. Breadth, i'2 c.d.m. Fresh and brackish water. — Antwerp; Tete de Flandre (P. Gaut.), mixed in small quantities in a gathering of the var. curvula. England (Comber, Kitton, Norman), Ireland (O'Mear.i). var. Kiitzingii Grun. ! (Neue, etc., i860; H.V.H. Atl., pi. 21, f. 14* ; Type No. 187), plate 7, fig. 277. More elongated and broader than the preceding ; central nodule elongate, larger. Transverse striae 2o'5, longitudinal striae 22*5 in 1 c.d.m. Length, 10 to 12 c.d.m. Breadth, 1*3 to 1*5 c.d.m. Fresh water. — Brussels (Del.). Frequent in Europe, West Indies, etc. (Grun.). var. acutiuscula Grun. ! (Grun. in H.V.H.'s Type No. 183). Form and striation as in the last, but slightly shorter, and with more acute apices. Length, 8 to 10 c.d.m. Breadth, 1*2 to 1*25 c.d.m. Fresh water. — Brussels (Del.). Prof. Cleve unites the two preceding varieties under the name of Pi. Kiitzingii. var. nodifera Grun. ! (Arct. D., p. 59; H.V.H. Atl., pi. 2T, f. 13* ; Type No. 184), plate 7, fig. 278. Central nodule elongated, with an oblique hyaline area ; longitudinal striae 22 or 23, transverse striae 17 to 20 in 1 c.d.m ; the median ones slightly radiate. Length, 6 to 10 cd.m. Freshwater. — Brussels (Del.). s 258 PLEUROSIGMA. var. curvula Grun. ! (Arct. D., p. 60; H.V.H. Atl., pi. 21. f. 3-5* ; Type No. 185), plate 7, fig. 279. Narrow, linear, scarcely lanceolate. Transverse striae 21 to 22*5 in 1 c.d.m. ; longitudinal striae 24 or 25 in 1 c.d.m. Length, 8 to 12 c.d.m. Breadth, 09 to i'i c.d.m. Brackish water. — Tete de Ftandre (Scheldt) at Antwerp (P. Gam). PI. tenuissimum. W. Sm. (S.B.D. i., p. 67, pi. 22, f. 213*), plate 28,tfig. 798. Very small, excessively narrow, feebly sigmoid, with very acute apices. Longitudinal striae, 24; transverse striae, 18 or 19 in 1 c.d.m. Length, 14 c.d.m. Breadth, 07 c.d.m. Marine. — Essex (W. Sm.), Liverpool (Comber; Stolt. ), Hull (Norman), England. Ireland (O'Meara). aa. Valves with apices rostrate produced. PI. Parked Harrison. (Q.J.M.S., i860, p. 104 ; h.v.h. Atl., pi. 21, f. 10*; Type No. 190), plate 7, fig. 280. Valve rather broadly lanceolate, with acute apices, longly acuminate rostrate, rostrum broad. Raphe dividing the apices of the valve into unequal moieties. Transverse striae about 19 in 1 c.d.m. Longitudinal striae about 22 in 1 c.d.m., forming, near the middle of the valve, flexed lines, producing ellipses by their intersections. Length, about 8 c.d.m. P'resh water.— Rare. Pond in the Park at Antwerp. Canal at Hasselt (Van den Born). England, Prof. Cleve considers this form to be a simple variety oi P. distortum. PI. distortum W. Sm. (Ann. N.H., 1852, p. 7, pi. 1, f. 10; Perag., p. 8, f. 32*), plate 28, fig. 799. Differs from the last by its feebly tapering rostrate apices and its finer striae, the longitudinal numbering 28 and the transverse 26 in 1 c.d.m. Length, 6 to 10 c.d.m. Marine. — England. Ireland. PI. Fasciola W. Sm. (S.B.D., i., p. 67, pi. 21, f. 211; H.v.H. Atl, pi. 21, f. 8* ; Types No. 191 and 192), plate 7, fig. 281. Valve narrow, lanceolate, with apices longly acuminate-rostrate; strongly sigmoid, rostrum very narrow. Raphe dividing the valve into equal moieties. Striae rather easily resolved, the longitudinal ones being about 23 and the transverse about 21 in 1 c.d.m. Length, about 10 c.d.m. Marine. — Antwerp (Scheldt), Blankenberghe. England, Ireland, and on all the coasts of Europe. PLEUROSIGMA. 259 var. arcuatum. {PL areuatum Donk.). Differs from the type form by its apices being more suddenly narrowed and moreover flexed, and by its slightly finer strife. Marine. — England, Chibburn Mouth, Druridge Bay, Cresswell (Donkin), Firth of Tay, Scotland. var. prolongatum. {PI. prolongation IV. Sin. .'). Much larger and more elongate than the preceding, apices longly produced, often flexed; transverse striae 21 to 23, longitudinal striae finer. Length, 21 to 27 c.d.m. Breadth, 1 to 1*5 c.d.m. Marine. — Blankenberghe, Antwerp. South Coast of England (W. Sin.). This form passes to the following form by every possible transition : — PI. macrum W. Sm. ! (S.B.D., i., p. 67, pi. 31, f. 276* ; h.v.h. Atl., pi. 21, f. 9*), plate 7, fig. 282, and plate 28, fig. 800. Valve very narrow, longly lanceolate, with apices feebly sigmoid, rather longly acuminate-rostrate, rostrum narrow. Raphe dividing the valve into equal moieties. Striae delicate, seen with difficulty, the longitudinal ones being 25 to 28, the transverse 25 to 27 in 1 c.d.m. Length, 21 to 27 c.d.m. Marine. — Rare: Antwerp (Scheldt), Blankenberghe. Sussex (W. Sm.), Hull (Xorman), Cheshire (Comber), Ireland (O'Meara), and probably on all the coasts of the North Sea. ** Frustules enclosed in gelatinous tubes, valves short, thick set. PI. eximium (Thwaites), H. Van Heurck {Colhtonema eximium Thwaites. Ann. & Mag., 1848, i., pi. 12F. ; pi. 12F; H.V.H. Atl., pi. ai, f. 2* ; Type No. 193), plate 7, fig. 283. Valve short, linear, with apices sigmoid, very obtuse. Raphe appearing strongly sigmoid, dividing the valve into equal moieties. Transverse stria? about 23 to 25, longitudinal stria? 27 or 28 in 1 c.d.m. Length, about 55 c.d.m. Marine. — Antwerp (Scheldt). England, Ireland, France. PI. scalproides Rab. (Fl. Eur. Aig., p. 241; h.v.h. Atl., pi. 21, f. 1*), plate 7, fig. 284. Valve short, linear-lanceolate, slightly sigmoid, with very obtuse apices. Raphe scarcely sigmoid. Longitudinal striae about 29 in 1 c.d.m ; transverse, about 22, rather more robust than the longitudinal striae, the median slightly radiate. Length, 6 to 7 c.d.m. Fresh water. — Not yet found in Belgium. Probably only a form of the last. 260 RHOICOSIGMA. GENUS 23.— RHOICOSIGMA GRUN, 1867 Emend H.P. 1891. Frustules more or less torsive, achnanthiform. Valves sigmoid, dissimilar ; the upper valve deli- cate, convex, with raphe straight or gently flexed ; the lower more robust, concave, with raphe very sigmoid and more or less carinate. Stria? decussate or rectangular. The genus Rhoicosigma includes about 15 species, of which only the two following belong to our latitude. Prof. Cleve does not recognise this genus, but places the species amongst the Pleurosigma Fig. 51. Rhoicosigma Oceanicum 1 1. P. [after H, Perogallo). { ANALYSIS OF SPECIES. Striae decussate, frustule arcuate, not achnanthiform . Stria; rectangular, frustule rather flexed, achnanthiform R. falcatum. R. compactum. Rh. falcatum (Donk.) Grun. (Grun. in Hedwigea, 1867; PI. falcatum Donkin ; H. Perag., p. 31, pi. 9, f. 25-27*), plate 28, fig. 801. Valves linear, gently sigmoid, with apices obtuse-rounded, decussate, fine ; girdle face gently arcuate, but not achnanthiform. Length, 15 to 18 c.d.m. Breadth, 1 -5 c.d.m. Marine. — Cresswell, Northumberland ! (Rev. R. Taylor in Coll. W. Arnott, No. 806^). Rh. COmpactum (Grev.) Grun. (in Cleve D. from West Ind, Arch., 1878, p. 9; PL compactum Grev. ; H. Per., pi. 10, f. 7-8*), plate 28, fig. 802. Valves lanceolate, with sub-acute apices, the upper with raphe straight, not projecting, the lower with raphe projecting very eccentrically on the valve. Transverse striae 20 to 24 in 1 c.d.m., the longitudinal ones being very fine. Girdle view achnanthiform, rather flexed. Length, about 14 to 18 c.d.m, Breadth, about 3-5 c.d.m. Marine,— Rather widespread (according to Mr. Peragallo), Bahusie (Lagerstedt), AMPHIPRORA. 26l (Group) Amphiprora Cleve, 1891. The genus Amphiprora was created in 1843 by Ehrenberg in his " Verbreitung und Einfluss, etc.," p. 113, from a form which no one has been able to identify. Prof. Pfitzer, in 1871, re-arranged the species which authors had up to that time described, and divided them into his Amphitropis and Phigiotropis. Prof. Cleve has lately re-constructed the genus in " Le Diatomiste " (1891), by subdividing the forms into a number of very characteristic groups. In his Monograph on the Naviculaceae Mr. Cleve adopts the following classification, which we accordingly accept : — Analysis of Sub-genera. r,- ,, ( Raphe sigmoid .... Girdle view J P lc e' ( Raphe not sigmoid, but bi-arcuate and very eccentric f Raphe central .... Girdle view 1 . ,- , e , ., , r / /Keel 01 both valves running in opposite not plicate , R , j di cti ns , ( Iropidoneis). ' • < . v ' 'I eccentric J l_ ,. \ Keel running in one direction Amphiprora. Auricula. f Orthotropis. i i Plagiotropis. ^Ampboropsis. GENUS 24.— AMPHIPRORA (EHR.) CLEVE, 1891. Valve carinate, with keel sigmoid through a more or less sinuous line of suture, united to the lower portion of the valve. Axial hyaline area absent, median area absent or small. Central nodule small. Connecting zone with longitudinal plaits. ANALYSIS OF SPECIES. f Keel with coarse puncta very slightly produced and very Alas not J distinct, about 4 in i c.d.m. . . . .A. alata. undulate. ) V. Keel without coarse puncta ; stria; fine . . .A. paludosa. ,. Aire undulate, festooned . . . . . . .A. ornata. 262 AMPHIPRORA. A. alata Klltz. (Baa, p. 107, pi. 3, f. 63 ; H.V.H. Atl., pi. 22, f. 11 and 12*; Type No. 195), plate 5, fig. 289. Valve linear elliptic, with apiculate apices. Keel sigmoid, furnished with elongated dots, about 4 in 1 c.d.m., and having on each side a very projecting sigmoid ala. Striae fine, punctate, about 14 to 16 in 1 c.d.m. Frustule generally torsive in a longitudinal direction, oblong elliptic, deeply constricted at the median portion, with rounded apices, connecting zone showing numerous longi- tudinal plaits. Length, 5 to 13 c.d.m. Fig. s2- Amphiprora alala. Marine and brackish water.- — Antwerp, Blankenberghe, Heyst, England, and on all the coasts of the North Sea. A. paludosa W. Sm. (S.B.D., i., p. 44, pi. 31, f. 269; h.v.h. Atl., pi. 22, f. 10*; Type No. 196), plate 5, fig. 290. Valve elliptic lanceolate, with apiculate apices. Keel sigmoid. Striae fine, 19 or 20 in 1 c.d.m. Frustule torsive, with girdle face deeply constricted at the median portion, apices rounded or truncate, connecting membrane with plaits fine, very approximate. Aire very projecting, forming near the apex a plait, which, when seen in the girdle view, assumes the appearance of an inflexion or undulation. Length, 4 to 8 c.d.m. Brackish water. — Antwerp, Blankenberghe. England (Comber, Kitton, Stolt. , Norm., and W. Sm.) and probably in all our regions. Observation, — It sometimes happens that a number of stria; become more vigorous than the others, as in the first of the two figures. var. duplex. (A. duplex Donk., T.M.S., 1858, vi., p. 28, pi. 3, f. 13; H.V.H. Atl., pi. 22, f. 15, 16* ; in Type No. 416), plate 5, fig 292. Valve with keel very sigmoid, lateral alae with inflexion very feeble or absent. Length, 4 to 6 c.d m. Marine.— Blankenberghe (2nd basin). Rare. England (Comber and W. Sm.). Ireland (O'Meara), and probably in all our regions. A. ornata Bailey. (Mic. Obs. made in South Carolina, etc., p. 38, pi. 2, f. 15 and 23 ; H.V.H. Atl., pi. 22 bis., f. 5*), plate 5, fig. 293. Frustules torsive, deeply constricted at the median portion, with alas gently undulate and festooned throughout their length. Striae radiate, finely punctate, QVJlt/^^ v^ \ CD) LIB TROPIDONEIS. CV/ 26 V 20 to 22 in 1 c.d.m. Connecting zone with numerous (8 to 10) well-marked plaits. Length, 4^5 to 8 c.d.m. Fresh water.— This beautiful and rare species has onlv been found once in Belgium, and that in scanty numbers, in a single gathering at Antwerp,' by Rev. P. Gautier. France (Temp. Perag., No. 258), Not yet found in the British Isles, GENUS 25.— TROPIDONEIS CLEVE, 1891. Valve very convex, carinate, with keel not sigmoid, sometimes straight, sometimes oblique. Median pores on the median line very approximate. Axial hyaline area absent ; central area absent or small. Striae parallel, formed of small beads, forming also more or less regular longitudinal lines: Con- necting zone simple, without plaits. Fig- 53- — Amphiprora maxima. Sec. I. ORTHOTROPIS Cl., 1891. — Central keel (straight), girdle face very strongly constricted. ANALYSIS OF SPECIES, f A pseudo-stauros round the central nodule ; stria; rather robust 0. maxima. < No pseudo-stauros ; strias delicate. . . .0. lepidoptera. | A true stauros ; valve simulating a navicula. V Pseudo-amphiprora staur- optera. O. lepidoptera (Greg.) Cleve. (Diat. of Clyde, p. 33, pi. 4, f. 59 ; H.V.H. Atl., pi. 22, f. 2-3* ; Type No. 197), plate 5, fig. 287. Valve lanceolate, with apices acute and slightly apiculate. Central nodule robust. Keel straight. Strise parallel, fine, 21 in 1 c.d.m. Frustule elongate-linear, oblong, constricted at the median portion, with apices rounded, slightly inflated. Length, 10 to 20 c.d.m. Marine. — Washings of mussels (Deby.). England (Kitton, Norman) (O'Meara), France ?, Holland. Scotland. Irelan 264 TROPIDONEIS. var. pusilla. (A. pusilla Greg. ; Diat. of Clyde, p. 32, pi. 4, f. 56, 56$ ; in Type No. 74, very rare), plate 29, fig. 804. Differs from the type form by its smaller size (4 to 6 c.d.m.), and its more approximate stride (24 in 1 c.d.m , according to Gregory). Marine. — Rare: Blankenberghe (H.V. H. ), Braydon, Norfolk (Kitton), Bangor (Stolt.), Loch Fine, Scotland (Greg.), Ireland (O'Meara). In his Diatoinacete of the Clyde (p. 33), Dr. Gregory refers to his A. lepidoptera a singular form which he figures as plate 4, fig. 59^ and 60. The same form has been figured by Dr. Ad. Schmidt (Nordsee, pi. 3, fig. 1*), under the name of Amphiprora obtusa (plate 29, fig. 803 of this work), and by Mr. Cleve (N.R.D. and Arct. Diat.), under the name of Naviatla arctua CI. In his Synopsis Prof. Cleve has erected it into a special genus, under the name of Pseudo-amphiprora. The form we refer to P. stauroptera, has its valves elliptic-lanceolate, with obtuse apices, a moderately broad stauros and striae fine (14 to 18 in 1 c.d.m.), punctate, parallel, and crossed on each side of the raphe by an arcuate line, somewhat constricted near the stauros. Length of the valve, n to 13 c.d.m. Breadth, 3 to 3^5 c.d.m. Marine. — North Sea (Greg. ) ; Finmark (Cleve). O. maxima Greg. (Diat. of Clyde, p. 35, pi. 4, f. 61 \ h.v.h., pi. 22, f. 4-5*), plate 5, fig. 288. Valve lanceolate, very slightly attenuate as far as the sub-acute apices, deeply depressed at the median portion, showing a robust arcuate ala on each side of the raphe. Striae about 14 in 1 c.d.m., leaving a stauroneiform area round the central nodule ; distinctly punctate, puncta forming longitudinal lines. Frustules rectangular, very broad, with apices rounded, deeply constricted at the median portion. Length, 11 to 16 c.d.m. Marine. — Not yet found in Belgium. England (Kitton), Scotland (Greg. ), Ireland (O'Meara), Heligoland. Sec. II. PLAGIOTROPIS Pfitz., i 87 i. — Valve with raphe eccentric, girdle face very feebly or not constricted. ANALYSIS OF SPECIES. f Frustules f Lateral plait conspicuous throughout slightly the length of the valve . . PL elegans. Valve with constricted \ margin J at the median j Lateral plait only well marked on the flexed ■ portion. l_ terminal third of the valve . . PI. Van Heurckii. regularly. t Valve with margin abruptly gibbous-inflated at the median portion . PI. gibDerula. Frustule without any constriction, only differing from a Nitzschia by the central nodule . . .PI. vitrea. TR0PID0NE1S. 265 PI. elegans (W. Sm.) Grun. (Amphiprora ekqans W. Sm., S.B.D., ii., p. 90; H.V.H. Atl., pi. 22, f. 1 and 6*; Type No. 199), plate 6, fig. 294. Valve lanceolate, narrow, very convex. Lateral plait very visible on the girdle side throughout the length of the valve. Striae about 13 in 1 c.d.m., very visible, granular, leaving a small hyaline area round the central nodule. Girdle face sub-quadrangular, with rounded apices. Length, 20 to 30 c.d.m. Marine.— Rare. Washing of mussels (Deby), Blankenberghe (H.V.H.), England (W. Sm. ; Kitton), Scotland (Greg.), Ireland (W. Sm.). Fig. 54- Plagiotropts elegans. PI. Van Heurckii Grun. (H.V.H. Atl, pi. 22 bis., f. 6, 7, 8* ■ Type No. 198), plate 6, fig. 295. Valve lanceolate, with apices strongly tapering. Lateral plait abruptly arcuate from the third of the valve, and only distinctly visible (in girdle view) on the terminal third of the frustule. Striae very delicate, about 22 in 1 c.d.m. Girdle face quadrangular, sub-elliptic, with median portion scarcely constricted. Length, about 6 c.d.m. Marine. — I made an abundant gathering of this interesting species in the spring and autumn of 1882 in the Retaining Basin of Blankenberghe. I had not previously noticed it. PI. vitrea (W. Sm.) Grun. (Arct. D., p. 67; h.v.h. Atl., pi. 22, f. 7-9*), plate 29, fig. 805. Valve lanceolate, with keel very eccentric, central nodule rather small, transverse striae fine, 17 to 19 in 1 c.d.m. Girdle face lanceolate, subtruncate, without any constriction. Length, 7^5 to io-5 c.d.m. Breadth of valve, 1-5 to about 2 c.d.m. Breadth of frustule, 8*5 to 14*5 c.d.m. 266 AURICULA. This singular form has all the appearance of a Nitzschia, and on first examination is only distinguished from one by the central nodule being more developed and the absence of dots on the keel. Marine. — Coasts of England, Scotland, Denmark, France (Calvados), Oldenburg. PI. gibberula Grun. (H.V.H. Atl., pi. 22 bis., f. 12, 13* without description), plate 29, fig. 806. Valve lanceolate, narrow, with acute apices and margins abruptly gibbous- inflated at the median portion. Striae fine, 18 in 1 c.d.m. Girdle face slightly constricted, appearing at first view to be achnanthiform in consequence of the presence of a projecting boss. Marine. — Firth of Tay (Scotland). Heligoland. Sec. III. AMPHOROPSIS Grun. (in Syn. 1883). — Valve with raphe eccentric ; keels running in same direction. A. recta (Greg.) Grun. (Amphiprora recta Greg. T.M.S., 1857, v., p. 56, pi. 1, f. 40; H.V.H. Atl., pi. 22 bis., f. 9-10. Cleve and Moll. Diat.) Frustules rectangular, gently con- stricted at the median portion, with rounded angles. Valve strongly unequi- lateral, without distinct alae. Transveise strise 21 to 24 in 1 c.d.m. Length, 8 to 9 c.d.m. Breadth, 2 to 3 cd.m. Marine. — Mouth of the Tay, Scotland (Greg.) Fig. 55. — Amplwropsis recta. Fig. 56.- GENUS 26.— AURICULA CASTR, 1873. Valves very convex, extremely- asymmetrical ; ventral and dorsal portions in different planes. Raphe raised like a keel, not sigmoid, oblique. Keels of the two valves turned on the same side. The two terminal nodules connected by a semi- mammiform elevation. Sutural zone complex. The genus Auricula was created by Count Castracane for a very curious form -Auricula Ampiiitritis. found in the Island of Lesina in the AURICULA. 267 Adriatic. Since then various analogous forms have been found, and Prof. Cleve has included in this genus Amphiprjra complexa and A. decipims. ANALYSIS OF SPECIES. Valve in the form of a boat, 20 to 22 strice in 1 c.d.m. Connecting zone without scattered coarse dots . . . . .A. decipiens. Valve reniforni. I Striae fine, 20 in 1 c.d.m. Striae robust 8 in 1 c.d.m. . A. complexa. . A. Amphitritis. A. decipiens (Grun.) {Amphoropsis decipiens Grun. in CI. and M. Diat., No. 309; H.V.H. Atl., pi. 22 bis., f. 11*; Amphiprora plicata Greg., Diat. of Clyde, p. 33, pi. 4, f. 57). Frustule rectangular, somewhat constricted at the median portion ; line of juncture sinuous, median area indistinct, striae 20 in 1 c.d.m. Sutural zone divided, having about three divisions in 1 c.d.m., broad on the dorsal face, narrower on the ventral face, and having about 22 stria; in 1 c.d.m. Length of frustule, 6 to n c.d.m. Breadth, 5 c.d.m. F;g 57- A mpkoropsis decipiens. Marine. — Coasts of Scotland (Greg., etc.) ! A. COmplexa (Greg.) CI. {Amphiprora complexa Greg, in Diat. of Clyde, p. 36, pi. 4, f. 62*), plate 29, fig. 807. Frustule subquadrangular, elongated, with median portion constricted. Valves arcuate, raphe inflexed. Connecting zone having 5 or 6 cuneate segments, semi-lunar, somewhat constricted at the median portion, finely striated, striae somewhat radiant, 20 in 1 c.d.m., bordered with a row of beads (about 8 in 1 c.d.m.) on the dorsal margin. Frustules : length, 9 to 12 c.d.m. ; breadth, about 7 c.d.m. Marine. — Coasts of Scotland (Greg ). The two following species which Prof. Cleve records from Sweden may perhaps also be found in the North Sea. A. insecta Grun. {A. mucronata H. L. Sm., Spec. Diat. Typ. No. 38 ; Am. Q.M.J., 1878, p. 17, pi. 3, f. 9*), plate 29, fig. 808. 268 GOMPHONEMA. A. minuta Cleve, (Syn. of the Nav. Diat., p. 21, pi. i, f. 7-8*), plate 29, fig. 809. A. Amphitritis Castr. (Diat. e Dalm.c. icone; Perag Diat. Villefr., p. 85, pi. 2, i. 18, and pi. 5, f. 41). Characters of the genus. Valve face with ventral margin arcuate, slightly constricted in the median portion with a submarginal raphe edged with a row of beads, abruptly depressed opposite the median nodule. Ventral margin concave, smooth as far as a very conspicuous line which connects the two terminal nodules, which are elongated, narrow. Striae en the valve face, radiate, bifurcating several times, 16 in 1 c.d.m. Length of valve, 8 to 10 c.d.m. Breadth, 6 c.d.m. Marine. — Lesina, Adriatic (Castracane). Yillefranche Bay, Mediterranean Sea (Peragallo). Balearic Isles (Cleve ! ). Tribe hi. — Gomphoneme.e. j Frustules curved in girdle view ; nodule or concave valve { All other forms ..... . Rhoicosphenia. . Gomphonema. GENUS 27.— GOMPHONEMA AG., 1824. Valve naviculoid, asymmetrical, one of the apices narrower than the other and cuneate. Frustules cuneate in valve view. Parasitic, sessile or stipitate, sometimes enveloped in a mucous mass. Endochrome formed of a single lamina, which rests at the centre on one of the sides of the connecting zone, and covers the two adjacent valves and the other side of the zone, on the middle of which is found the line of separation. Prof. Cleve dismembers the genus Gomphonema, and separates from it three species (G. Herculanum, mamilla, and cltgans) to constitute his genus Gomphoneis. These three species have, as common characteristics, transverse costae, between which is found a double row of small alternating beads (as in N. Smithii, etc.), and traversed by a marginal sulcus, more or less distinct. Fig. 58. Gomphonema gemi- natum. GOMPHONEMA. 269 ANALYSIS OF SPECIES. * Asymmetrica Grun. Valve having a rather large isolated dot near one of the sides of the central nodule. Median strife alternately ) long and short. \ Valve without a hyaline area, slightly stauronei- form. Median stria; not alternately long and short ; no large rounded Valve hyaline having a area. hyaline area, more or less stauronei- form. L A large round hyaline area Valve very large, inflated at the two apices .G. geminatum. Valve rather small, not inflated at the lower apex Valve not lanceolate rostrate. r Upper apex apiculate. Upper apex not apiculate. Valve lanceolate-rostrate . G. constrictum. f Valve inflated at me- dian portion . G. acuminatum. \ Valve not inflated at [ median portion . G. Augur. ! Median portion and J upper apex inflated G. subtile. (, No portion inflated . G. montanum. . G. parvulum. At least f Valve naviculoid, with the two apices one of the nearly similar . . . G. gracile. apices of jomphonemoid, with the two lissimilar . G. micropus. the valve subacute. I Valve goni| I. apices di The two apices almost equally obtuse. f Valve nar- ( Valve very large, row, elong- rather broad . G. Vibrio. ate, length -| ■ 6 to 8 times j Valve of medium size its breadth. [ or small, narrow . G. intricatum. Valve not very elongate, length L about 4-5 times its breadth . G. angustatum. . G. ventricosum. * * Symmetrica Grun. No isolated dot ; the two sides of the valve similar, ( Fresh water : Pseudo-stauros very visible ; stria; radiate '. . G. Olivaceum. V Marine : No pseudo-stauros ; striae sub-parallel . G. exiguum. /. Stri f- ' 5 ar>d 16* ; Type No. 264), plate 9, fig. 370, 371. Valve very slightly arcuate, elongate, narrow, with parallel margins, apices produced subrostrate, but not capitate; striae well marked, finely divided transversely, about 8 in 1 c.d.m. at the median portion, much closer at the apices. Connecting membrane with about 15 rather irregular striae in 1 c.d.m. formed of puncta rather coarse, but faintly visible. Length, 3 to 15 c.d.m. Fresh water. — Common. EUNOTIA. 301 forma curta. (H.V.H. Atl., pi. 33, f. 15*), plate 9, fig. 370. Small, almost straight. forma elongata. (H.V.H. Atl., pi. 33, f. 16*), plate 9, fig. 371. Long, feebly arcuate. var. ventricosa Grun. (H.V.H. Atl, pi. 33, f. 19^*), plate 9, fig. 372. Ventral margin showing an embossment in the median portion. var. undulata Ralfs. (H.V.H. Atl., pi. 33, f. 17*; Type No. 265), plate 9, fig. 373. Ventral margin showing a median embossment, dorsal margin with three to five embossments. var Soleirolii Kiitz. (H.V.H. Type, No. 266). Form with septate frustules (double internal valves) in consequence of an imperfect division. E. Faba. (Ehr.) Grun. (Himantidium Soleirolii IV. Sm, part ; H.V.H. Atl., pi. 34, f. 34*; in Type No. 274), plate 9, fig. 374. Valve reniform, elongated, with somewhat visible striae, 10 to 12 in 1 c.d.m., finely divided transversely ; girdle face almost always showing septa arising from an imperfect division {var. Soleirolii W. Sm.). Length, 3 to 5 c.d.m. Fresh water. — Not yet found in Belgium, very doubtful if indigenous. France, England (Comber), Scotland, Ireland (O'Meara). 77. Frustules not united in filaments. a. Frustules free, not parasitic on other plants. E. Veneris KlitZ. (Baa, p. 40, pi. 30, f. 7 ; E. incisa Greg. ; H.V.H. Atl., pi. 34, f. 35 A*), plate 30, fig. 826. Valve of medium size, with ventral margin almost straight, dorsal margin arcuate, apices subacute. Striae fine, 16 or 17 in 1 c.d.m. Length, about 4 c.d.m. Fossil. — Mull deposit, Scotland (Gregory). var. obtusiuscula Grun. (H.V.H. Atl., pi. 34, f. 35B* ; in Type No. 271). plate 30, fig. 827. Ventral margin somewhat concave, apices obtuse. Fossil. — Sweden, England. E. tridentula Ehr. (Verb., p. 126, pi. II., i, f. 14; H.v.H. Atl, pi. 34, f. 31 var* ; in Types Nos. 309 and 347), plate 9, fig. 375. 3ar. gracillima THALASSIOTHRIX. 32 I A. formosa Hassall. (Microscopical examination of the Water supplied to the Inhab. of London, 1850; T.M.S., i860, viii., p. 149, pi. 7, f. 8 ; H.V.H. Atl., pi. 51, f. 19 and 20*), plate 11, fig. 439. Valve narrowly linear, diminishing somewhat in breadth from the base, which is very strongly capitate, to the superior apex, the head of which is much smaller ; stria? fine, about 17 in 1 c.d.m., interrupted by a very narrow pseudo-raphe and a rather large hyaline area in the basal inflation. Girdle face strongly inflated at the inferior portion, very slightly so at the superior portion. Length, 7 to 10 c.d.m. Fresh water. — The type-form has not yet been found in Belgium, but it has been found in England (Kitton, Comber, Roper, Norman, Arnott.), Scotland (Baxter Coll., 2790), Ireland (O'Meara), France, and Denmark. var. gracillima (Hantzsch) Grun. (H.V.H. Atl., pi. 5T, f. 22*; Type No. 345), plate 11, fig. 440. Valves much narrower than in the type-form. Rather common at Antwerp in the town ditches and neighbouring waters. — England, Denmark, Ireland (O'Meara). var. infiata. (H.V.H. Atl., pi. 51, f. 23*; in Type No. 345), plate 11, fig 441. Girdle face abruptly inflated in its inferior third. Antwerp, mixed with the preceding. Denmark. var. Blcakeleyi. (A. BleakekyiVI. Sm. ! ; H.V.H. Atl., pi. 52, f. 1*), plate 30, fig. 838. Frustules short, enlarged, dilated at the base. Length, 4-5 to 5 c.d.m. Marine — Harwich (Bleakeley), Norfolk (\V. Sm.. ! Kitton), East Coast (Norman). var. Ralfsii. (A. Ralfsii. W. Sm.). Frustule still shorter and relatively broader than the preceding. Length, 3-5 to 4-5 c.d.m. Fresh water. — England (W. Sm., Norman). GENUS 43.— THALASSIOTHRIX.— CLEVE AND GRUN. (1880). Valves quadrangular, with apices unequally developed, margins furnished with spines or elevated points, between which are seen short marginal striae. x 322 THALASSIOTHRIX. \ Fig. 78. Thalassioth rix longisiima var. antarctica. This genus is confined to marine species. Mr. Grunow in the first instance also included in it Synedra Nitzschioides. But now the genus should only consist of Th. Frauenfeldii Grun. (H.V.H. Atl., pi. 37, f. 11 and 12*), plate 30, fig. 839, and Th. longissima CI. and Grun. (fig. 78), the longest known diatom since it attains to 3 to 4 mm. in length. It inhabits the Arctic Seas. Thai, curvata Castr. (Diat. Challenger, p. 55 pi. 24, f. 6*), plate 30, fig. 840, is too incom- pletely described and figured to form a judgment, on the form, without at least having an authentic specimen at one's disposal. According to the figure it does not appear to differ much from Synedra (Thalassionetna) Nitzschioides, if it were not for the slight flexure of the frustules. Tribe VIII.— Fragilakie^e. \ Frustules rectangular in girdle view ; valves with distinct pseudo-raphe, regularly striated ...... Fragilaria. Girdle face f Frustule with connecting zone undulate-arcuate, valves rectangular. lanceolate ..... CymatOSira. Valves with -j ! scattered | Frustules with valves arcuate, connecting zone arcuate and I puncta. ( attenuated near the apices, which are inflated . Campyloaira. \£\ «v FRAGILARIA. a. b. Fig. 79. — Fragilaria virescens. 323 GENUS 44.— FRAGILARIA LYNGBYE, 1819 (Char. Emend). Valves symmetrical without costa?. Frus- tules rectangular, united in long filaments or chains. In the section Staurosira the endo- chrome is similar to that of the Synedra. In the species contained in the section Fragilaria, a. Valve, b. Girdle view, it is granular. Pseudo- raphe narrow and scarcely visible [Fragilaria). Pseudo- raphe distinct (Staurosira). ANALYSIS OF SPECIES. Valve linear or linear-elliptic, with apices produced ; striae 17 in 1 c.d.ni. Fresh water species . . F. virescens. Valve elliptic-oval, with apices acuminate-rostrate. Fresh water . . . . . F. undata. Valve elliptic-elongated, scarcely silicious ; striae very delicate, 24 in 1 c.d.m. Marine . . . F. striatula. Valve linear-narrow, with apices inflated ; striae almost invisible, 31 or 32 in 1 c.d.m. Marine . . F. hyalina. Valve linear, very narrow, inflated at the median portion. Fresh water .... Striae formed of distinct beads . F. Crotonensis. F. capucina. Striae not margi- nal. Striae very robust, i with beads more or less confluent or simulating costae. Valves small, broad- ly oval or cruci- form . Valve small, either cruciform, or inflated or constricted at the median portion, striae fine . F. construens. Striae marginal Valve narrowly lanceo- late, with apices in- flated, capitate. Fresh water - . F. tenuicollis. „ Valve regularly oval . F. mutabilis. Valve cruciform, rather large, with robust costae . . F. Harrisonii. . F. brevistrlata. I. Fragilaria. — Pseudo-raphe very narrow and scarcely visible. F. virescens Ralfs. (Ann. and Mag., 1843, XII., p. no, pi. 2, f. 6; H.V.H. Atl., pi. 44, f. 1* ; Type No. 309), plate n, fig. 442. Valve linear or linear elliptic, with apices attenuate and often rostrate- obtuse. Pseudo-raphe scarcely visible. Striae fine, distinctly punctate, about 17 in 1 c.d.m. Frustules quadrangular, elongate, united in long filaments. Length of valves very variable. Mean length, 2 to 6 c.d.m. Fresh water. — Southern region of Belgium: Namur (P. Gaut.). Pleinevaux (Delogne). Ard. Lieg. (De Wild.). England, Scotland, Ireland, and throughout Europe. 324 FRAGILARIA. F. undata W. Sm. (S.B.D., ii., p. 24, pi. 60, f. 377*), plate 30, fig. 841. Valves elliptic or longly oval, with apices acuminate and more or less rostrate. Stria? delicate, 17 in 1 c.d.m. Filaments separating easily, and frustules then cohering by their angles. Length, 2 to 5 c.d.m. Fresh water. — England (W. Sm.), Lock Kinnord Dep. Scotland (Davidson), var. constricta. Valves constricted at the median portion. Fresh water.— Scotland (Mull Dep. W. Sm.), F. Striatula Lyngb. (Hydroph. Dan., p. 183, pi. 63A; H.V.H. Atl., pi. 45, f. 12*), plate 30, fig. 842. Valve narrowly lanceolate, with apices somewhat attenuate. Pseudo-raphe very narrow. Striae very delicate, 24 in 1 c.d.m. Frustules quadrangular, elongated, with connecting zone plicate, in long filaments, very easily deformed, imperfectly silicious. Marine. — England, Scotland, Ireland, France (probably Belgium), Germany, Norway. F. hyalina (Kiitz.) Grun. {Diaioma hyalina Kiitz., Baa, p. 47, pi. 17. f. 20 ; H.V.H. Atl., pi. 44, f. 14 and 15* ; Type No. 310), plate ir, fig- 443- Valve linear, narrow, hyaline, with apices feebly inflated, terminal nodules distinct; striae very fine, scarcely visible, 31 or 32 in 1 c.d.m. Girdle face quadrangular, elongated, with apices rounded, sometimes inflated, connecting zone showing numerous fine longitudinal striae. Length, 45 to 7*5 c.d.m. Marine. — Not yet found in Belgium. England, Ireland. F. Crotonensis (A. M. Edwards) Kitton. ! (Science Gossip, 1869, p. no, f. 81*), plate 11, fig. 444. Valve linear, very narrow, slightly inflated at the median portion, with apices capitate; striae 15 in 1- c.d.m. Girdle face strongly inflated at the median portion, and slightly enlarged at the apices. Frustules united in filaments at the middle. Length, 4 to n c.d.m. Fresh water. — Town ditches at Antwerp (only once observed). Ireland (O'Meara). FRAGILARIA. 325 var. prolongata Grun. (H.V.H. Atl., pi. 40, f. 10* ; Type No. 319), plate 11, fig. 445. Valve very narrow, with apices not capitate. Length, about 10 c.d.m. Fresh water. — Botanical Gardens, Brussels (Del.). II. STAUROSIRA. — Pseudo-raphe broad, often more or less lanceolate. F. capucina Desmazieres (Piantas Crypt. Ed. I. (1825), No. 453 ; H.V.H. Atl., pi. 45, f. 2*), plate 11, fig. 446. Valves linear, narrow, with apices somewhat produced rostrate. Margin of valve marked with very distinct coarse beads, continued towards the internal portion by delicate stride, 14 or 15 in 1 c.d.m. Frustules united into long filaments. Length, 3 to 6 c.d.m. Fresh water. — Common everywhere. var. mesolepta (F. mesolepta Rab. ; H.V.H. Atl., pi. 45, f. 3* ; Type No. 312), plate 11, fig. 447. Valve strongly constricted at the median portion, with apices rostrate and sometimes capitate ; striae 17 or 18 in 1 c.d.m. Fresh water. — Rather common. var. acuta Grun. (H.V.H. Atl., pi. 45, f. 4*), plate 11, fig. 448. Valve narrowly lanceolate with sub-acute apices. var. acuminata Grun. (H.V.H. Atl., pi. 45, f. 8*), plate 11, fig. 449- Valve narrowly lanceolate, with apices longly and narrowly rostrate ; stria? 18 in 1 c.d.m., delicate. Fresh water. — Paliseul (Delogne). F. construens (Ehr.) Grun. ! (Oestr. Diat., p. 371; h.v.h. Atl., pi. 45, f. 26, E and D figures on the right and left, and f. 27*) ; in Type No. 190), plate 11, fig. 450. Valve broadly oval, constricted somewhat below the median portion into rostrate-capitate apices, giving a cruciform appearance. Pseudo-raphe lanceo- late. Strise fine, about 15 in 1 c.d.m. Length, about 1*5 c.d.m. Freshwater. — Somewhat rare; England (Kitton), Ireland (O'Meara) ; found throughout Europe. var. Venter. (H.V.H. Atl., pi. 45, f. 21B, 22, 23, 24B, and- 26 (upper and lower * figures) ; in Type No. 190), plate 11, fig. 451. Valve lanceolate, with obtuse apices, inflated at the median portion. Freshwater. — Brussels (Delogne). Sheene Dep. Aberdeen (Temp, and Perag., No. 443)- 326 FRAGILARIA. var. binodis Grun. (H.V.H. Atl., pi. 45, f. 24A. and 25*), plate 11, fig. 452. Valve lanceolate, with apices rostrate, median portion constricted. Fresh water. — Antwerp, rather common and parasitic on Nitzschia Sigmoidea. Ard. Lieg. (De Wild.). England (Kitton), &c. F. tenuicollis Heib. (Consp. Diat. Danic, p. 62, pi. 5, f. 13*), plate 30, fig. 843 and 843 bis. Valves very narrowly lanceolate, linear, with apices rostrate-capitate. Pseudo-raphe narrow ; stride very robust, somewhat radiant, convergent, approximate, about 10 in 1 c.d.m. Girdle face quadrangular, very elongated, somewhat produced at the apices. Length, 2*5 to 5 c.d.m. Fresh water. — Denmark (Heiberg). Ireland (O'Meara). var. intermedia (Fr. intermedia Grun. ; H.V.H. Atl., pi. 45, f. 9*), plate 30, fig. 844. Only differs from the preceding by the presence of a small median unilateral hyaline space. Striae robust, 9 or 10 in 1 c.d.m. Freshwater. — England, Ormesby Broad, Norfolk (Kitton in W. Arn. Coll., Nos, 914-915 tinder the name of Frag, tenuicollis. ) F. Harrisonii (W. Sm.) Grun. ! (Oest. Diat, p. 368; H.V.H. Atl, pi. 45, f. 2S* ; Type No. 316), plate 11, fig. 453. Valve sub-cruciform, with rounded angles, apices obtuse or sub-obtuse. Pseudo-raphe lanceolate. Striae very robust, 4 or 5 in c.d.m, formed of puncta, confluent and simulating costae. Length, about 2 to 5 c.d.m. Fresh water. — Very rare. Mountainous parts of Belgium : Bouillon (Delogne). England (W. Sm, Kitton), New River (Grove). F. mutabilis (W. Sm.) Grun. ! (Oest. Diat,, p, 369, H.V.H. pl. 45, f. 12* ; Type No. 315), plate 11, fig. 454. Valves elliptic or, more rarely, linear-elliptic ; striae very robust, with beads confluent, 8 or 9 in 1 c.d.m. Length, 1 to 2*5 c.d.m. Fresh water. — Brussels (Delogne) Louvaine (P.G.) Ard. Lieg. (De Wild.). England (Kitton), New River (Grove). F. brevistriata Grun. ! (H.V.H. Atl, pi. 45, f. 32*; Type No. 31S), plate 11, fig. 455. Valve lanceolate, with apices produced rostrate ; striae very short and marginal, 13 or 14 in 1 c.d.m. Length, 1*25 to 2 c.d.m. Fresh water. — Brussels (Delogne). Ard, Lieg. (De Wild.). CYMATOSIRA. 327 GENUS 45.— CYMATOSIRA GRUNOW, 1862. Valve lanceolate, with coarse puncta, Gir- dle face rectangular, undulated. Frustules in filaments. a, b. Fig. 80. Cymatosira Lorenziana. a. Valve view. b. Girdle view. C. Belgica Grun. ! (H.v.H. Atl., pi. 45, f. 38-41*), plate n, fig 456. Valve lanceolate, very slightly attenuate up to the apices, which are sub- acute, with coarse puncta, sparse, but generally leaving a pseudo-raphe of greater or less breadth. Frustules rectangular, in short filaments, with girdle face constricted near the apices. Length, 1*5 to 3 c.d.m. Marine. — Rare : Blankenberghe. GENUS 46.-CAMPYLOSIRA GRUNOW, 1882. a. b. Fig. 81. Campylosira cytnbelliformis. a. Valve view. b. Girdle view. Valve cymbelliform, with rostrate apices, dorsal margin arcuate, ventral margin gently concave, covered with sparse puncta, without visible pseudo-raphe. Girdle face arcuate, constricted near the apices. Frustules united in filaments. C. cymbelliformis (A. Schmidt) Grun. ! (Synedra anus j3 minor Grun. olinu ; H.V.H. Atl., pi. 45, f. 43*; Type No. 320), plate n, fig- 457- A single species, with characteristics of genus. Mean length, 4 c.d.m. Marine. — Very common on all our coasts. 328 CLAVICULA. Valves with apices similar. Valves with apices dissimilar, the inferior attenuated like a wedge. Tribe IX. — Raphoneide^;. Valves elongated, with apices inflated, puncta interrupted by two hyaline lines ..... Clavicula. Frustules usually solitary, with girdle face quadrangular or linear. Valves with pseudo-raphe of greater or less breadth Raphoneis. I Frustules united in twos, attenuated between the middle and apices ; suture serrated ; valves with coarse puncta without a distinct pseudo-raphe .... Girdle face rectangular, the valve only differing from that of true Raphoneis by its inferior apex being cuneate . Terebraria. Trachysphania Girdle face cuneate. ( Valves with small terminal pseudo-nodules without pseudo-raphe . . Peronia. No pseudo- nodule, but a pseudo- raphe. GENUS 47. Valves gomphonemoid, normal puncta . . . Sceptroneis. Valves with coarse round mar- ginal beads . . Grunoviella. Valves with coarse puncta very elongated into the form of button-holes . . Opephora. -CLAVICULA PANT., 1886. ,'^r [ecnf oo^ cAPo :<>£> ["to { Valve with apices inflated, inflations more or less rhomboidal ; coarse puncta leaving a hyaline line on each side of the valves. This genus consists at present of a very small number of fossil species found in Hungary by Dr. Pantocksek and of some others, also fossil, from Japan, described by Professor Brun. (After a Photograph). Fig. 82. Clavicula polymorpha var. delicalula. TEREBRARIA. 329 GENUS 48.— TEREBRARIA GREV., 1864. Valve elliptic, oblong, with apices attenuate, furnished with 3 or 4 lines of coarse distant puncta. Girdle face quadrangular, attenuated near the apices, punctate. a. b. Fig. 83. Terebraria Barbadensis Grev. after Greville. a. Valve view. b. Girdle view. This genus consists of one species Terebraria Baibadensis Grev. found in the deposit of Cambridge Estate (Barbados). GENUS 49.— RAPHONEIS EHR, 1844. DC DM OGc rp OQC .w> ooc 3D DCS 84. 85. Fig. 84. Raphoneis gemmifera. forma curia, . Fig. 85. Raphoneis scalaris. Valves lanceolate or elliptic, with striae trans- verse, moniliform, generally somewhat radiant, very distinct, with a more or less conspicuous pseudo-raphe. Apices without nodules, often showing fine scattered puncta. Girdle face narrow, linear. The genus Raphoneis includes a large number of species, both living and fossil, but very many of them appear to us to be only modifications of R. amphiceros. 33° RAPHONEIS. ANALYSIS OF SPECIES. f pSeudo- f Strise curved, the median shortened; valve raphe very broad, lanceolate . . . R. amphiceros. All beads , narrow, of equal ' linear ' btnae stralSht- somewhat radiant ; valve size. '. I linear or narrowly lanceolate . . R. Belgica. | Pseudo-raphe of greater or less breadth, but attenuate at the L median portion . . . . , r Surirella. Valve bordered with a row of beads much smaller than those in the centre L of the valve . . . . . R Liburnica. R. amphiceros Ehr. (Bericht. der Bed. Ac, 1844; H.V.H. Atl., pi. 36, f. 22 and 23*; Type No. 276), plate 10, fig. 394. Valve broadly lanceolate, with apices rostrate and sometimes sub- capitate ; striae more or less curved, very radiant, 5 or 6 in t c.d.m., formed of coarse puncta placed at equal distances and forming almost straight longi- tudinal lines, the median, and sometimes those near it, shortened. Apices of valve covered with irregular puncta. Mean length, 4 to 7 c.d.m. Marine. — Common. Blankenberghe, Ostend and Antwerp (Scheldt). Coasts of England, France, and Germany. var. rhombica Grun. (H.V.H. Atl., pi. 36, f. 20 and 21*), plate 10, fig- 395- Shorter, more inflated, with apices feebly or scarcely rostrate. Mean length, 3 to 5 c.d.m. R. Belgica Grun. ! (in h.v.h. Atl., pi. 36, f. 25, 29 and 30*; Type No. 277), plate 10, fig. 396. Valve narrowly lanceolate or linear, with apices rostrate-obtuse or sub- obtuse ; striae 7 to 9 in 1 c.d.m., straight or gently radiant, all of equal length, leaving a narrow pseudo-raphe, composed of puncta forming straight longi- tudinal lines. Valve with apices covered with puncta, sparse, rather fine. Mean length, 8 to 9 c.d,m. Marine. — Blankenberghe. R. Surirella (Ehr. ?) Grun. (H.v.h. Atl., pi. 36, f. 26 and 27a* ; in Type No. 277), plate 10, fig. 397. Valve narrowly elliptic or slightly lanceolate, with apices obtuse, pseudo- raphe narrow, linear, dilated only at its apices ; striae 8 in 1 c.d.m., gently radiant, with coarse puncta forming longitudinal lines, more or less curved. Mean length, 4 to 4*5 c.d.m. Marine.— Common at Blankenberghe. Coast of England (Kitton). var. Australis. (H.V.H. Atl, pi. 36, f. 27^* ; in Type No. 277), plate 10, fig. 398. Pseudo-raphe very broad, constricted only at the median portion. Marine, — Blankenberghe. TRACHYSPHENIA. 331 R. Liburnica Grun. ! (Neue etc., 1862, p. 69, pi. 7, f. 6 ; H.V.H. Atl., pi. 36, f. 33*), plate 10, fig. 400. Valve broadly elliptic, with narrow pseudo-raphe ; puncta arranged in radiant lines, about 4 in 1 c.d.m., central puncta very large, diminishing towards the margin, which bears right round its edge a row of much smaller beads, about 6 in 1 c.d.m. Mean length, 3 c.d.m. Marine. — Blankenberghe, second Basin. — Very rare ; only one specimen observed. Fig. 86. Trachysph enia Austi aiis, var. Aucklandica. GENUS 50.— TRACHYSPHENIA P. Petit, 1877. Valves cuneate, furnished with coarse puncta, arranged in longitudinal and transverse rows. Pseudo- raphe rather narrow. Frustule and connecting zone rectangular. Upon the whole, the Trachysphenia is nothing more than a Raphoneis, one of whose apices is narrower than the other. Only a single species is known, the Trachysphenia Austtalis P. Pet. (fig. 86), which was found in the Isle of Campbell, at Cape Horn, &c. The valves are 3*5 to 5 c.d.m. in length and have six rows of beads in 1 c.d.m. GENUS 51.— SCEPTRONEIS EHR., 1844. ■OO C'.l Valves cuneate, with structure similar to that of the Raphoneis ; girdle face and connecting zone cuneate. Fig. 87. Sceptroneis Caducens. 332 CRUNOVIELLA. Sceptroneis Caduceus Ehr. (in Bed. Acad., 1844, p. 264; H.V.H. Atl., pi. 37, f. 5*; Typ2 No. 279), plate 10, fig. 399. Valve bacillar, very elongated, with inferior portion gently cuneate. Median portion very slightly inflated. Superior apex strongly capitate. Pseudo-raphe narrow, somewhat enlarged in the median inflation. Strise, about 4 or 5 in 1 c.d.m., formed of coarse puncta; apices covered with fine puncta, radiant or sparse. Length, 10 c.d.m. Marine. — Very rare. I have observed it once in the second Basin at Blankenberghe and another time at Antwerp in the Scheldt. Mr. Deby has observed it at Flessingue at the mouth of the Scheldt. Scotland (Gregory). GENUS 52.— GRUNOVIELLA H.V.H. , 1892, Gen. Nov. Valve sub-cuneate, furnished with a row of coarse marginal beads ; pseudo-raphe lanceolate ; girdle face rectangular. I dedicate this genus to my excellent friend, the eminent diatomographer, Mr. Grunow, who has described the type-form. Fig. 83. Grunoviella ge??imata. G. gemmata (Grun.) H.V.H. (Sceptroneis? gemmata Grun. Hedw. V., p. T46 ; H.V.H. Atl., pi. 37, f. 3* ; Type No. 280). Valve lanceolate, cuneate, very narrow, with apices gently capitate, furnished with a row of very coarse marginal beads, 4 to 4*5 in 1 c.d.m. ; pseudo-raphe broadly lanceolate. Length, 6 to 9 c.d.m. Fossil. — Mors, Jutland (Moller) and Franz Josef Land (Grun.) Observation. — The girdle face appears to indicate that we are not dealing with true beads, but rather a row of very short costa?. I include in the same genus Sceptroneis marina (Greg.) Gran. (H.V.H. Atl., pi. 37, f. 2*), plate 30, fig. 845, from the Balearic Isles. PERONIA. 333 GENUS 53.— PERONIA BREB AND ARN., 1868. Frustule and valve cuneate and similar to a Gomphonema, but differing from it by the absence of central nodule and raphe. Frustules sessile solitary or united by twos. Fig. 89. Peronia erinacea. Peronia erinacea Breb. and Arn. (Q.J.M.S., 1868, viii., p. 16; Gomphonema Fibula Breb. ohm; H.V.H. Atl., pi. 36, f. 19*; in Types Nos. 67, T26, and 274), plate 10, fig. 389. Valve narrow, cuneate, with superior apex rostrate-capitate ; terminal nodules distant from the apices; striae rather broad, but obscure, about 15 or 16 in 1 c.d.m., interrupted by a well marked pseudo-raphe. Girdle face cuneate, with marginal striae. Length, 4 to 5 c.d.m. Fresh water. —Rare. Cornimont (Del.), France (Breb.), England (W. Sm.). Fig. 90. Opephora Schwartzii. GENUS. 54.— OPEPHORA P. PETIT, 1888. Valve cuneate, furnished with long costae, distant. Girdle face cuneate. Between the costae are found small fine beads as in some Navicula. The type-species is the O. Schwartzii (Gr.) P.P. from Brazil and the Seychelles. Mr. Paul Petit also includes in the genus Fragiiaria parijica Grun. (H.V.H. Atl., pi. 44, f. 20-22*), plate 30, fig. 846, but as it has the girdle face rectangular, like Sceptroneis marina Grun. and Fragi- laria pinnata F/ir., these three forms ought to be included in our genus Grunoviella. 334 GLYPHODESMIS. Tribe x. — Plagiogramme^e. Valves showing in the median portion a transverse hyaline space. . Plagiogramma. f Valves without a central pseudo-nodule . . Dimeregramma. Pseudo-nodule very coarse, projecting ; Valves without a transverse hyaline space. I Valves furnished with a central nodule. valves cuneate Omphalopsis. | Central nodule rather small ; valves (_ not cuneate . Glyphodesmis. GENUS 55.— GLYPHODESMIS GREV, 1862. Valves navicular, furnished with a central pseudo-nodule and terminal smooth spaces. Pseudo-raphe distinct. Puncta more or less quadrangular, usually arranged in longitudinal and transverse rows. Girdle face quadrangu- lar, attenuate between the smooth apices and the connecting .zone. Frustules united in filaments. Authors have enumerated a dozen forms of Glyphodcsmis, but many of these do not really belong to the genus. The two following, coming from the North Sea, are true types of the genus. Fig. 91. Glyphodestnis Wilhamsonii. a. Girdle view. b. Valve view ANALYSIS OF SPECIES. Beads rather small, extending throughout the valve, frustule attenuate between the central nodule and the smooth spaces . . . G. Williamsonii. Beads very coarse, marginal ; frustules somewhat attenuate between the smooth apices . . . . . . G. distans. Glyphodesmis Williamsonii (Greg.) Grun. (H.v.H. At)., pi. 36, f. 14*; Diadesmis Willia?nsonii Greg.! Diat. of Clyde, p. 25, pi. 2, f. 40*), plate 30, fig. 847. Valve linear, narrow, constricted at the median portion, with apices produced- rostrate. Pseudo-raphe very conspicuous, dilated round the central pseudo- nodule and at the apices, where it leaves an oblong smooth space. Striae formed of coarse sub-quadrangular granules, forming longitudinal and trans- verse rows, the latter about 8 in 1 c.d.m. Girdle face quadrangular, attenuate between the central nodule and the smooth spaces ; similarly attenuate (on the short margin of the frustule) between the smooth spaces and the connect- ing zone. Length, 6 to 8 c.d.m. Marine. — Coasts of England (Kitton), Scotland (Loch Fyne, Greg. !) and of Ireland. OMPHALOPSIS. 335 Gl. distans (Greg.) Grun. (H.v.H. Atl., pi. 36, f. 15, 16*- Denticuia distans Greg. ! Diat. of Clyde, p. 23, pi. 2, f. 36), plate 30, fig. 848. Valves broadly lanceolate, with apices obtuse rounded, bearing on the margins a row of beads (or short costae?), very coarse, 5 or 6 in 1 c.d.m.; central nodule coarse, indistinct, terminal smooth spaces round, very large. Girdle face quadrangular, slightly attenuated between the two smooth apices. Length, 3 to 6 c.d.m. Marine. — Coast of Scotland (Lamlash Bay, Greg. !), Ireland, Sweden. /TTt GENUS 56.— OMPHALOPSIS GREV., 1863. Valve cruciform, with apices rounded, obtuse, smooth, separated from the rest of the valve by a transverse diaphragm. Pseudo-raphe narrow, enlarged round the central nodule, which is very coarse. Girdle face rectangular, with rounded angles. Frustules united into a filament. \^=JJ Fig. 92. Omphalopsis Australis lirev. a. Valve view. b. Girdle view. This genus consists of a single species O. Australis, represented in the text. The valve is sometimes elongated, some- times short, thick-set ; the striae, about 4 in i c.d.m., are very distinct and formed of small distinct beads. Marine.— Seychelles Isles (Coll. Weissf. !). Dred- ging off Woodlark Island (Roberts). Fig- 93- Dimercgramma fulvum. a. Girdle view. b. Valve view. GENUS 57.— DIMEREGRAMMA RALFS., i860. Valve with striae interrupted by a pseudo-raphe, broad and dilated at the median portion, with apices smooth. Without a central transverse smooth space. Frustules united in filaments. This genus, in fact, only differs from Glyphodesmis by the absence of a central pseudo-nodule. The genus Dimere- gtamma includes about a dozen species, three of which belong to our shores. 336 DIMEREGRAMMA. ANALYSIS OF SPECIES. ' Valve more or less broadly lanceolate ; pseudo-raphe lanceolate . . D. minor. Valve linear f or narrowly Valve not inflated at the median portion ; puncta tine . D. fulvum. lanceolate ; J [ pseudo-raphe "1 linear, Valve somewhat inflated in the middle ; puncta robust . D. marinum narrow (, D. minor (Greg.) Ralfs. (Greg. Diat. of Clyde, p. 23, pi. 2, f. 35, sub Denticula; H.V.H. Atl., pi. 36, f. 10 and iifl*), plate 10, fig. 392. Valve lanceolate, with apices obtuse, smooth ; pseudo-raphe very gently dilated towards the median portion; striae 10 in 1 c.d.m. formed of well marked puncta, rather distant, not forming longitudinal lines. Frustules quadrangular, attenuate underneath the apices, which are obtuse-truncate. Length, 3 to 4 c.d.m. Marine. — Blankenberghe, Ostend. Scotland (Lamlash Bay and Loch Fyne, Greg. ! Cumbrae, sand washings, Baxter Coll., No. 2478. Ireland (O'Meara). var. nana. (Denticula nana Gre*., Diat. of Clyde, p. 23, pi. 2, f. 34; H.V.H. Atl., pi. 36, f. wb, 12, and 13*), plate 11, fig. 393. Valve inflated at the median portion, with apices abruptly attenuate; stria? 14 in 1 c.d.m. ; girdle face as in the type-form, but shorter. Length, 1 to 2 c.d.m. Marine. — Blankenberghe, Ostend. Mixed with the preceding. England (Stolt.), Scotland. D. fulvum (Greg. !) Ralfs. (in Pritch. Inf., p. 790; Denticula fulva Greg. ! ; H.V.H. Atl, pi. 36, f. 7*), plate 30, fig. 849. Valve very narrowly linear, with apices gently capitate, rounded ; striae about to in 1 c.d.m., distinctly granular. Girdle face rectangular, narrow. Length, 4 to 7 c.d.m. Marine. — Scotland (Lamlash Bay, Greg. !), Ireland, Sweden. D. marinum (Greg. !) Ralfs. (in Pritch. Inf., p. 790; Denticula marina Greg. ! ; H.V.H. Atl., pi. 36, f. 9*), plate 30, fig. 849 bis. Valves lanceolate, linear, gently inflated at the median portion, with apices obtuse, rounded. Raphe rather broad, lanceolate, somewhat dilated at the median portion, terminated by rounded smooth spaces. Stria;, 4 in 1 c.d.m., formed of very coarse puncta. Girdle face rectangular, very narrow, some- what attenuate near the apices. Length, 8 to n c.d.m. Marine. —English Channel (Temp, and Perag., No. no). Scotland (Lamlash Bay, Greg. !) Ireland (O'Meara). TUBULAR I A. GENUS 57 fe.-TUBULARIA BRUN, 1894. By the side of Dimargramma should be placed, according to Prof. Brun, a new genus, which he has described under the name of Tubularia Brim, in Le Diat., 1S94, ii., p. 88. Frustule tubular, somewhat twisted, flat on the girdle face. Valve transversely striated : raphe obscure ; apices opening obliquely and furnished with a large hyaline space. Only one species up to the present time. Tubularia pistillaris J. Brun, found in Jackson's Paddock (Barbo). Very rare. Repre- sented in the text. Fig- 94- Tubularia pistillares. GENUS 58.— PLAGIOGRAMMA GREV, 1859. Valve having at the median portion a hyaline space, which is generally transverse, often furnished in the middle with a pseudo-ocellus or furnished with two robust costse, which are prominent in the girdle face : apices hyaline ; striae punctate, puncta distant. Frustules united in filaments. The Plagiogramma are amongst the most beautiful examples of diatoms. About 50 species are known and these inhabit southern regions. The two about to be described are the only species peculiar to the North Sea. Among the Plagiogramma are also included two species of Denliciila, D. intetrupta, and D. icvis of Gregory, found in Lamlash Bay, Scotland, but they are very problematical species, the valves of which have not been described. Fig- 95- Plagiogramma Gregorianum. ANALYSIS OF SPECIES. Striae formed of coarse puncta sub-quadrangular; pseudo-ocellus broad, girdle face scarcely or not attenuate at the apices . P. Gregorianum. I Stria? formed of small puncta ; pseudo-ocellus narrow, girdle face strongly i_ attenuate at the apices .... P. Van Heurckii. Y 338 PLAGIOGRAMMA. P. Gregorianum Grev. (Q.J.M.S., 1859, vii., p. 208, pi. 10, f. 1 and 2; H.V.H. Atl., pi. 36, f. 2*; in Type No. 104), plate 10, fig. 390. Valve oblong lanceolate, with hyaline median portion showing an elongated pseudo-ocellus, bordered with two robust costae, apices showing a large smooth space. Striae 9 in 1 c.d.m., formed of coarse puncta, sub-quadrangular, forming longitudinal lines ; girdle face quadrangular, obtuse. Length, about 2 to 4 c.d.m. Marine. — Blankenberghe. England (Stolt. ), Scotland (Greg. ), Ireland (O'M.), France (Breb. ), Bahnsie (Lagerst), Denmark (Heiberg). P. Van Heurckii Grun ! (h.v.h. Atl., pi. 36, f. 4*), plate 10, fig. 391. Valve narrowly lanceolate, with apices generally somewhat rostrate capitate, smooth, with a narrow hyaline transverse band bordered with two costae, far from robust; strias 1 1 or 12 in 1 c.d.m., formed of small puncta, forming longitudinal lines. Girdle face very slightly constricted from the middle to underneath the apices, which are dilated truncate. Median portion only showing one robust costae, formed by the nearness of the apex of the two costae visible on the valve. Individuals united in rather long filaments. Length, 1*5 to 4*5 c.d.m. Marine. — Found on one occasion on a jetty between Heyst and Blankenberghe, and at another time in the mud sediment ot the second Basin at Blankenberghe. Surface of the River Dee, England (Stolterfoth) COHORT OF TABELLARIINE^. ANALYSIS OF TRIBES. f Frustules genuflexed ...... Entopylese. Frustules not as above. ( Valves pyriform (more or less in the shape of a pear) that is cuneate-oval ..... Licmopliorese. f Frustules forming a spiral band . . Meridionese. Valves not • /False septa very distinct, seldom as above. "| Frustules J reduced to knobs . . TaPellariese. I not spiral. J ^ v False septa usually absent . DiatomeEe. Tribe XL— Entopyle^:. Frustules showing rudimentary septa (diaphragms) ; valves furnished with costee ....... Entopyla. Frustules without internal septa ; valves furnished with costae . . Gephyria. ENTOPYLA. 339 GENUS 59.— ENTOPYLA EHR, 1841. Valves furnished with dissimilar costae, the inferior concave with terminal nodules, the superior convex without nodules. Girdle face curved arcuate, showing several false internal septa. Frustules parasitic, united in short chains, stipitate. Fig. 96, — Entopyla Australia, 34< GEPHYRIA. Fig. 97. — Entopyla incurvata. The genus Entopyla includes eight species, either fossil or inhabiting tropical regions. E. Australis Ehr. is represented in figure 96, reproduced from figures by an esteemed correspondent Mr. C. Janisch (zur Charakteristik des Guanos), and shows on the right the girdle face, and underneath the convex valve, the two other valves showing coarse terminal nodules are concave valves. E. incurvata (Arn.) Grun., often met with in collections under the name of Gephyria incurvata, is represented in figure 97. GENUS 60.— GEPHYRIA W. ARNOTT, i860. Differs from Entopyla by the absence of false septa. The two genera are closely allied, and might, with some reason, be united into a single genus. Six species of Gephyria have been described, but they are all found out- side the confines of Europe, either living or fossil. LICMOPHORA. 34' Fig. 98. — Gephyria media. Tribe XIL— LicmophorEvE. f Frustules cuneate, showing on the valve face a single vitta rounded, and more or less approximate to the enlarged apex . . . Licmophora. Frustules cune.Ue, showing on the valve face a large number of transverse septa, simulating the steps of a ladder (scalariform) . . . Climacosphenia. GENUS 61.— LICMOPHORA (AGARDH), 1827. Valves more or less cuneate, with monili- form striae, pseudo-raphe conspicuous. Frus- tules cuneate, showing internal septa. Endo- § chrome granular, sparse on the internal sur- 5 face of the frustules. The genus Licmophora, as it exists at the present time, results from the fusion of the three former genera Licmophora, Podosphenia and Rhipi- dophora, founded on inadmissible differences, and which Kvitzing based on the comparative breadth of the valve and the presence or the absence of a stipes. About thirty Licmophora have been described, the larger number of these forms presenting only the smallest differences, and many given as species ought to be placed in the rank of varieties only. Fig. 99. Licmophora Californica. 342 LICMOPHORA. Licmophora are found in all regions of the globe, the North Sea producing a large number, as the following table demonstrates. ANALYSIS OF SPECIES. /. — Frustules scarcely septate. ' Valve very long and narrow, of almost equal breadth at the two apices . L. flabellata. Valve very gently attenuated from the summit to the base . L. Juergensii. ( Valve abruptly attenuated towards the lower \ L. Dalmatica. Valve with superior apex con- siderably broader than the inferior. Valve Valve f Valve large, broad, 24 strias in abruptly J abruptly 1 c.d.m. . . L. gracilis. attenuated { attenuated near the base. towards 1 the inferior | Valve small, narrow, 25 striae ^rd. ^ in 1 c.d.m. . . L. Anglica. II. — Frustules profoundly septate. C Valves very broadly cuneate, strias very robust . . L. Valves rather broad, about 27 striae in 1 c.d.m. Valves not broadly cuneate ; strias fine or very fine. Valves abruptly attenuated near the base. Valves infinitesi- mally attenuate. at the middle of the valve Ehrenbergii. paradoxa. Valves very Girdle face broadly cuneate. f Striae rather fine, about 13 in 1 c.d.m. in the middle of the valve . . . L. Lyngbyei. "1 I Strias very fine, about 30 in 1 c.d.m. in the middle of the ^ valve . . . L. tincta. Septa very arcuate, about 23 strias in 1 c.d m. in the mid- dle of the valve . L. communis. i Septa slightly arcuate, about 30 strias in 1 c.d.m. in the mid- L die of the valve . . L. nubecula. i Girdle face very narrowly cuneate, about 16 ^ strire in 1 c.d.m. in the middle of the valve . L. tenuis. /. — Frustules scarcely septate. a. Apices almost of the same breadth. L. flabellata (Carm.) Ag. (Consp., p. 41 ; h.v.h. Atl., pi. 46, f. 2-3* ; Type No. 323), plate 31, fig. 852. Valves excessively long and narrow, cuneate, lanceolate, attenuate towards the inferior apex, which is inflated, subcapitate. Striae about 30 in 1 c.d.m. Girdle face cuneate, very narrow. Length, up to 30 c.d.m. Marine.— North Sea. England (W. Sm., Ralfs, Mrs. Griffiths). Scotland (Dickie, Carmichael), Ireland (O'Meara). LICMOPHORA. 343 aa. Superior apex considerably broader than the inferior. L. Juergensii Ag. (Consp., p. 42 ; H.v.n. Atl., pi. 46, f. 10, n*; Type No. 324), plate 31, fig. 850. Valve long, clavate, very slightly attenuated from the base to the summit. Striae delicate, about 18 in 1 c.d.m. Girdle face broadly cuneate ; septa straight, indistinct. Length, 6 to 9 c.d.m. Marine —Coasts of the North Sea. Found in England. Ireland (O'Meara). L. Dalmatica (Kutz.) Grun. ! (Rhipidophom Kutz., Bac., pi. o. f. 7 ; H.V.H. Atl., pi. 47, f. 7* ; Type No. 326), plate 11, fig. 459*. Valve narrowly cuneate, acute at the inferior portion, rounded at the superior. Striae very fine, about 30 in 1 c.d.m. Girdle face strongly cuneate. Length, 2 to 6 c.d.m. Marine. — Blankenberghe, with the preceding. England (Comber. Stolt.). Scotland. France (De Bn§b). var. tenella (H.V.H. Atl., pi. 47, f. 8*), plate 11, fig. 459^. Smaller and more delicate than the type-form. L. gracilis (Ehr.) Grun. (in Hedw., 1867, p. 34; h.v.h. Atl., pi. 46, f. 13*), plate 31, fig. 851. Valve clavate, abruptly attenuate towards the inferior third ; pseudo-raphe broad; striae delicate, 20 to 22 in 1 c.d.m. Girdle face narrowly cuneate. Length, 8 to 10 c.d.m. Marine. — Coasts of the North Sea. England (Stolt.). L. Anglica (Kutz.) Grun. ! (R/iipidop/ior.i Kutz., Bac, pi. 7, f. 27, v., 2 and 4; H.V.H. Atl., pi. 46, f. 14*), plate 11, fig. 458. Valves clavate, abruptly attenuate towards their inferior third, and with subparailel margins ; stria? 25 in 1 c.d.m. Girdle face much inflated at the superior portion, very cuneate, with superior angles rounded. Length, 2 to 5 c.d.m. Marine. — Blankenberghe on algae on the jetties. Coasts of England (Stolt., Norm.). 344 LICMOPHORA. II. — Frustules profoundly septate. L. Ehrenbergii (Kiitz.) Grun. (in Hedw., 1S67, p. 36; H.V.H. Atl., pi. 47, f- io, "*)i Plate 3L fig- 853. Valves broadly cuneate, somewhat obtuse at the base ; superior apex rather acute; pseodo-raphe broad; stride very robust, about 8 to 10 in 1 c.d.m. ; frustule narrowly cuneate. Length, 10 to 14 c.d.m. Marine. — Coasts of the North Sea. England (Kitton). English Channel. Ireland (O'Meara). var. ovata (Z. ovata W Sm. ; H.V.H. Atl., pi. 47, f. 13*; Type No. 327), plate 31, fig. 854. Valve much broader, apices more obtuse. Marine. — Found in England. L. paradoxa (Lyng.) Ag. (Ag. icon. Aig., 1829; H.V.H. Atl., pi. 47, f. 10-12*), plate 31, fig. 855. Valve short, oboval, subpyriform, abruptly attenuate towards the inferior third. Pseudo raphe rather broad ; strire very fine, about 27 in 1 c d.m. at the middle of the valve. Girdle face very broad at the superior portion, with septa rather strongly arcuate towards the superior third. Length, 3*5 to 6 c.d.m. Marine. — North Sea. England (Ralfs), Scotland (Greville, Dickie), Ireland (O'Meara). L. Lyngbyei (Kutz.) Grun. ! (Podosphmia Kutz., Baa, pi, 10, f. 1 and 2; H.V.H. Atl., pi. 47, f. 16*; Type No. 321), plate 11, fig. 460. Valve clavate, regularly attenuate up to the inferior third, which is attenuate, and with subparallel margins, the internal septa being distinctly seen through the transparent valve ; striae fine, 14 or 15 in 1 c.d.m. in the superior, and 1 2 in 1 c.d.m. in the inferior portion. Girdle face rather broad in the superior portion, with angles very rounded. Length, about 5 c.d.m. Marine. — Ostend (Westendorp, No. 797). Noith Sea. England (Kitton), Ireland (O'Meara). L. tincta (Ag.) Grun, (in Hedw., 1867, p. 35; H.v.H. Atl. pi. 48, f. 13-15*; Type No. 328), plate 31, fig. 856. CLIMACOSPHENIA. 345 Valves very narrow, abruptly attenuate near the inferior third. Pseudo- raphe indefinite. Stride very fine, about 30 or 31 in 1 c.d.m. near the middle of the valve. Girdle face very broad, abruptly truncate at the base, rounded at the summit ; septa gently arcuate. Marine. — North Sea ? L. communis (Heib. ?) Grun. (in h.v.h. Atl., pi. 48, f. 8, 9*), plate 31, fig. 857. Valves obovate, pyriform, short, with inferior apex subacute ; pseudo-raphe indefinite, striae fine, 22 to 24 in 1 c.d.m. at the middle of the valve. Girdle face very broad, with septa strongly and abruptly bent towards the superior third. Marine. — On all the coasts of Europe. L. nubecula (Kutz.) Grun. (Kaspisch. Meere, p. 123; H.V.H. Atl, pi. 48, f. 18*), plate 31, fig. 858. Valve very gently attenuate ; striae very fine, about 31 in 1 c.d.m. Girdle face rather narrow, with septa slightly arcuate. Marine. — North Sea? Coasts of France (Atlantic Ocean at Granville, De Breb. ). L. tenuis (Kutz.) Grun. (in Hedw, 1S67, p. 35 ; h.v.h. Atl., pi. 48, f. 21*; Podosphenia gracilis W. Sm. !), plate 31, fig. 859. Valve long and narrow, very slightly attenuate, striae fine, about 16 in 1 c.d.m. Girdle face long, very narrowly cuneate, with septa rather strongly bent near the superior apex of the frustule. Marine. — North Sea. England (Jersey, W. Sm. !), Norway, etc. GENUS 62.— CLIMACOSPHENIA EHR., 1843. Valve oboval, lanceolate or subclavate, linear, very finely striated transversely, showing neither pseudo-raphe nor nodules, leaving the scalariform openings of the underlying septa visible through the valves. Frustules cuneate, showing the apices of the transverse costae and a connecting membrane, with robust moniliform striae. 346 CLIMACOSPHENIA. Four species of Climacosphenia are known, all of which are marine or fossil ; the best known is Climacosphenia monihfera Ehr., represented in the Fig. ioo. — Climacosphenia monilifera. text (fig. ioo), which inhabits warm regions and is frequently found in collections. It is the true type-form of the genus. By the side of Climacosphenia have been ranked Climaconeis, of which there are two species known — CI. Lorenzii Grun. and CI. Frauenfeldii Grun. We are not acquainted with the first, but the second is nothing else than Stictodesmis Australis Grev., which we have already mentioned at end of the description of the Naviculae (p. 236). The raphe and the nodules of this form do not permit us to consider it as belonging to the Pseudo-raphidese. CI. Frauenfeldii appears to be only a variety of CI. Lorenzii. The genus Climaconeis has been established on the bacillar form and the internal septa of the valve. MERIDION. Tribe XIII. — Meridione/E. 347 Frustules and valves cuneate, united in a spiral filament Meridion. GENUS 63.— MERIDION AGARDH., 1824. Differs from the genus Diatoma by the cuneate form of the valves and of the frustule in girdle view. Endochrome as in the following genus. Fig. 101. — Meridion circulare. This genus ought to be suppressed, but in that case it would be logically necessary to suppress all cuneate genera, such as Gomphonema, etc. Wl. circulare Ag. (Ktitz., Baa, pi. 7, f. 16 ; h.v.h. Ati, pi. 51, f. 10-12* ; Type No. 343), plate 11, fig. 474. Valves oval, lanceolate, or clavate, with apices rounded, obtuse, showing transverse costa? rather distant (about 3 in 1 c.d.m.) ; pseudo-raphe indistinct. Stria? fine, about 16 in 1 c.d.m. Girdle face cuneate, with margins appearing somewhat undulated by the beginnings of the costre, which terminate insensibly near the connecting zone. Frustules united in a spiral filament. Length, 2 "5 c.d.m. Fresh water. — Not very rare. England (Norman), Scotland, Ireland (O'Meara). 348 DIATOMA. var. constrictum. (H.V.H. Atl., pi. 51. f. 14, 15*; Type No. 344), plate n, fig. 475, Differs from the type form with which it is allied by intermediate forms (see H.V.H. Atl., pi. 51, f. 13), by the superior apex being rostrate capitate. Fresh water.— Rarer than the type-form. Fays-les-Veneurs (Del.). Ard. Lieg. (De Wild.). England (Norman). var. Zinkenii. (M. Zinkenii. K'ittz. ; H.V.H. Atl., pi. 51, f. 17*), plate 11, fig. 476. Connecting zone showing internal septa. Tribe XIV. — Diatome.e. ( Valves without a keel (carina) ..... Diatoma ( Valves furnished with a carina, the latter not punctate . . Denticula GENUS 64.— DIATOMA DE CANDOLLE, 1805 (Char. Emend.). Valves lanceolate or linear, furnished with transverse costal, but without a carina ; pseudo-raphe rather indistinct. Frustules with girdle face quadrangular, elongated, united into short filaments or zig- zag chains. Endochrome granular, scattered on the internal surface of the frustules. ANALYSIS OF SPECIES. f Frustules forming f Valves broadly lanceolate, or linear-elliptic ; apices a filament in scarcely or not rostrate or capitate . . D. vulgare. zig-zag ; valves j with delicate \ costse. i Valves narrowly linear, with apices more or less (I. Diatoma.) [_ capitate . . . D. elongatum. Frustules f united in short j Valves lanceolate, with apices sometimes slightly filaments ; produced . . . . D. hiemale. valves with very robust | Valves linear, narrow, with apices rostrate or ros costse. j trate capitate ... D. anceps. . (II. Odontidium.) [ I. DlATOMA. — Filaments in zig-zag ; costce rather delicate. D. vulgare Bory (Diet, d'hist. natur., 1828, Bot, pi. 20, f. 1; H.V.H. Atl., pi. 50, f. 1-6*; Type No. 335), plate 11, fig. 465. DIATOM A. 349 Valves broadly lanceolate or linear, with apices scarcely or not rostrate or capitate. Pseudo-raphe indistinct. Costas delicate, about 5 or 6 in 1 c.d.m. ; Fig. 102. Diatoma vul&art. stria? fine, delicately punctate, 16 in 1 c.d.m. Girdle face quadrangular, with straight margins. Length, 4 to 5 c.d.m. Fresh water. — Common throughout Europe. van linearis. (H.V.H. Atl., pi. 50 f. 7, 8*), plate it, fig. 466. Valve elongate and broadly linear, with apices sometimes somewhat capitate. D. elongatum Ag. (Syst., p. 4; h.v.h. Atl., pi. 50, f. 14*, 18-22*; Type No. 337), plate 11, fig. 467. Valve linear, very narrow, with apices more or less capitate. Costa? delicate, about 7 in 1 c.d.m. Striae fine, about 17 in 1 c.d.m. Girdle face very narrow, constricted at the median portion. Length, 4 to 7 c.d.m. Fresh and brackish water. — Throughout Europe, and especially in our latitudes. var. tenue. (£). tenue Ag. ; H.V.H. Atl., pi. 50. f. 14a and i>* ; in Type No. 337), plate 11, fig. 468. 350 DIATOMA. Very narrow, delicate, with apices feebly capitate ; length, 3 to 5 c.d.m. The type-form and the variety, which are allied by various intermediary forms, appear in the brackish water gathering (Type Xo. 337) made at Nieuport (West. No. 799). Ireland (O'Meara). var. hybrida Grun. (H.V.H. Atl., pi. 50, f. 10-13*), plate 11, fig. 469. Valves more robust, more broadly linear, strongly capitate, with head extending considerably beyond the breadth of the valve. Length, 5 to 8 c.d.m. Brackish water. — Common : Antwerp. var. Ehrenbergii. (D. Ehrenbergii Kutz.). Only differs from the last mentioned variety by its valves being attenuated underneath the capitate apex. II. ODONTIDIUM AUCT. — Frustules united in short filaments ; costce very robust. D. hiemale (Lyngb.) Heib. (Odontidium Kutz., Bac., p. 44, pi. 28, f. 4; H.V.H. Atl., pi. 51, f. 1 and 2* ; Type No. 340), plate 11, fig. 470. Valve lanceolate, with apices sometimes somewhat produced, furnished with 6 to 10 robust transverse costce; striae fine, about 20 to 22 in 1 c.d.m. Girdle face quadrangular, elongated. Length, 3 to 5 c.d.m. Freshwater. — Mountainous regions: Wiry (Del.), Ard. Lieg. (De Wild.). England, Wales (Ralfs), Scotland (Greville, Arnott), Ireland (O'Meara). var. mesodon. (O. mesodon Kutz. ; H.V.H. Atl., pi. 51, f. 3 and 4* ; in Types Nos. 347 and 461), plate 11, fig. 471. Valves short, very broadly lanceolate, with only 2 to 4 transverse costre, placed in the middle of the valve. Length, 1-5 to 2-5 c.d.m. Mixed with the type-form at Wiry (Del.). England, Scotland (Arnott, Gregory), Ireland (W. Sm., O'Meara). D. anceps (Ehr.) Grun. (Fragilaria Ehr. ; H.V.H. Atl., pi. 51, f. 5-8*; Type No. 341), plate [i, fig. 472. Valve linear, narrow, with apices rostrate or rostrate capitate, with 6 to 14 robust costse, having often an oblique direction; striae about 21 in 1 c.d.m. Girdle face quadrangular, elongated. Length, 2 to 5 c.d.m. Fresh water. — Mountainous regions ; Mogimont (Del), England, Norway. var. anomalum (O. anomahan IV. Sm.; H.V.H. Atl., pi. 51, f. 9*; Type No. 342), plate 11, fig. 473. Differs from the type-form by internal septa shown on girdle view. Fresh water.— Mogimont (Del.). Scotland (Balfour), Ireland (O'Meara). DENTICULA. 351 GENUS 65.— DENTICULA KUTZING, 1844. Z'J enables various Valves more or less lanceolate, fusnished with a carina and transverse costae, between which punctate striae can be seen. Frustules solitary or in short chains, with girdle face quad- rangular, showing the capitate apices of the costae. A dozen species of Denticula are known, and these are scattered throughout the world. The presence of a carina the Denticula to be associated with the Nitzschia, and with this genus authors have arranged them. Fig. 103. Denticula elrmns. ANALYSIS OF SPECIES. f Girdle face very broad, showing costas with capitate apices ; valves with obtuse apices, carina indistinct, strire 14 to 17 in 1 c.d.m. . . D. elegans. j Girdle face broad. Valve with apices subacute, carina conspicuous ; striae i, fine, about 17 in 1 c.d.m. . . . . . D. tenuis. I Girdle face very narrow. Valves with apices acute, carina invisible ; stria; (^ very fine, about 30 in 1 c.d.m . . . D. subtilis. D. elegans Kutz. (Baa, p. 44. pi. 17, f. 5; H.v.H. Atl., pi. 49, f. 14, 15*; in Types Nos. 48 and 257; D. ocellata IV. Sm.), plate 31, fig. 860. Valve linear, lanceolate, with apices obtuse rounded, carina obscure, 4 or 5 costas in i c.d.m.; striae robust, strongly punctate, about 17 in 1 c.d.m. Girdle face very broad, rectangular, with rounded angles, showing the apices of the costas, strongly capitate. Length, 2 to 3 c.d.m. Breadth of girdle face, about 1 c.d.m. Fresh water (on rocks, etc.). — England, Scotland (Balfour), Ireland (O'Meara). var. thermalis (D. thermalis Kutz.; H.V.H. Atl, pi. 49, f. 17, 18*), plate 31, fig. 861. Valve somewhat broader, with apices less obtuse. Striae, 14 in 1 c.d.m. Thermal waters. — Sweden (Lagerstedt). 352 DENTICULA. D. tenuis Klitz. (Baa, pi. 18, f. 8; H.V.H. Atl., pi. 49, f. 28 to 31* ; Type No. 332), plate 11, fig. 461. Valves longly lanceolate, with apices more or less produced-rostrate, carina conspicuous, costse 7 or 8 in 1 c.d.m. ; striae fine, 17 in 1 c.d.m. Girdle face broad, showing the carina in the form of a median inflation. Length, 1*5 to 4-5 c.d.m. Fresh water. — England (Norman, Johnson, W. Sm.). Scotland (Dickie, Arnott). France, Belgium (Ard. Lieg. De Wild. var. infiata. (D. inflata W. Sm) ; H.V.H. Atl., pi. 49, f. 32 to 34*; Type No. m\ plate 11, fig. 462. Valve broadly lanceolate, very slightly attenuated up to the apices. About 3 costa? in 1 c.d.m. Fresh water. — Brussels (Delogne), England (Norman. W. Sm.), France. var. frigida. (Df-37: H.V.H. Atl., pi. 52, f. 13 and 14* ; Type No. 348 ; Gomphogramma rupestris A. Br.), plate 11, fig. 489 a. Valve elliptic-lanceolate, showing 2 to 5 costae, transverse, robust; stria; fine, about 18 in 1 c.d.m. Girdle face generally showing two pairs of internal septa. Frustules solitary or united by twos or threes or more. Length, 75 to 2-5 c.d.m. Fresh water in mountainous regions. Very rare. Alle(Del.) on damp rocks. England ? • This diatom closely resembles Odontidium mesodon, but it is easily differentiated from it, in the girdle face, by the presence of false septa. Fig. 107. Tetracyclus rupestris. 35§ TABELLARIA. B. Entetracyclus (Ra/fs). T. lacustris Ralfs (in Ann. and Mag. Nat. Hist., xii., pi. 4, f. H.V.H., in Type No. 349). 2 ; Fig. 108. — Tetracyclus lacustris. Valve more or less cruciform or elliptic, lanceolate, with median portion strongly ventricose, venter rounded, showing 4 to 1 2 costae, transverse, curved near the median portion ; striae moniliform, excessively faint, and scarcely visible, about 25 to 30 at the middle of the valve, pseudo-raphe narrow. Frustulcs in long filaments, showing numerous septa. Fresh water.— England, Wales (Ralfs.), Scotland (Gregory), Ireland (Win. Sm.) var. marginata (Ehr.), W. Sm. {Tetracyclus eniargina/us, IV. Sm. ; Biblarium emarginatum Ehr.) Valve more regularly cruciform, with inflation excavated. Fresh water.— England. Scotland (Grew, Greg.), Ireland (W. Sm.). STYLOBIBLIUM. 359 Fig. log. Salacia Boryana. Salacia Pant, 1889. Dr. Pantocsek in his Bacill. Ung., 1889, p. 68, gives the following diagnosis of the sub-genera Salacia : — " Frustula a latere vis a rectangula, cum angulis obtusis, valde elevata, convexa, tabulata, in fascias compressas conjuncta, cum dissepimentis abreviatis transversis, longioribus perpendicularibus,. inflatis et lineis perpendicularibus striolatis. Valva elliptice- lanceolata, cum dissepimentis transversis, ad polos cum spacio hyalino nudo ; spacium interseptale striolatum." He admits one species, S. Boryana, which is figured in the text after one of my photographs. On the grounds that the name of Salacia had previously been given by Linneus to a genus of the Phanerogamia, Professor De Toni has altered the name from Salacia to Castracania. As there cannot be any confusion between the two I do not see the necessity of the change. But I only notice the genus Salacia as a memorandum, as I consider that ^. Boryana should be included in the genus Tetracyclics. The species presents the closest affinity with T. rhombus. GENUS 70.— STYLOBIBLIUM EHR, 1845. Fig. no Stylobiblium divisum. Valves orbicular, furnished with costs, without pseudo-nodules. Frus- tules cylindrical, free, furnished with numerous internal septa. This genus only includes four species, all fossil ; one from Japan, the other three from Oregon. The figure opposite represents 6". divisum Ehr. from Oregon, taken from one of our photographs. 36° RHABDONEMA. GENUS 71.— RHABDONEMA KUTZ, 1844. Valve lanceolate or linear, with pseudo-raphe distinct, apices usually smooth, furnished with costal or robust beads. Girdle face showing numerous false septa. Frustules united in filaments, shortly stipitate. Endochrome granular, sparse. The genus includes about 15 species, living or fossil, but only three belong to our shores. Fig. in. — Khabdonema arcualum. ANALYSIS OF SPECIES f „. ,, , , r f False septa having only a single perforation ; Girdle face showing fine valves furnished with costal alternate with beads alternating with moniliform strise . . . R. arcuatum. transverse costce ; "1 valves with smooth j Fa]se septa having three perforations . valves aPlces- |_ furnished with costse, resolvable into beads . R. Adriaticum. _ Girdle face not showing transverse costas ; valves entirely striate . R. minutum R. Adriaticum Kiitz. (Bac, p. 126, pi. 18, f. 7; h.v.h. Atl, pi. 54, f. 11-13* ; Type No. 360), plate 12, fig. 486^. Valves narrow, linear elliptic, with apices smooth, showing false costae, 8 to 9 in 1 cd.m., which can be resolved into approximate beads. False septa with three openings, furnished with transverse costos and a pseudo- r.iphe. Girdle face shewing numerous false septa, the intervals between which are filled with transverse costas (7 or 8 in 1 cd.m.), and between each of which are found one or two rows of very fine puncta. Length, 6 to 9 cd.m. Breadth, up to 20 cd.m. each frustule. Marine.— Not yet found in Belgium. England (Norman, W. Sm.). Scotland (Arnott), Ireland (W. Sm. , O'Meara). France, Bahnsie, Sweden, &c. R. arcuatum (Agardh) Kutz. (Bac, Pl. 18, f. 6; h.v.h. Atl, pi. 54, f. 14-16*; Type No. 361), plate 12, fig. 487^. RHABDONEMA. 361 Valves lanceolate, with apices smooth, pseudo-raphe well marked, furnished with costae, 8 in 1 c.d.m., alternating with rows of rather robust beads. False septa furnished with only a single very large opening. Girdle face showing numerous false septa, the intervals between which are filled with transverse costae (7 to 7-5 in 1 c.d.m.), between each of which are found two rows o( very fine beads, alternating. Length, 4 to 6 c.d.m. Marine.— Antwerp, in the Scheldt (Belleroche). England (Kitton, Comber, Norman, Stolt.). Scotland (Arnott). Ireland (O'Meara). Norway. R. minutum Kutz. (Baa, pi. 21, f. ii., 4 ; h.v.h. Atl., pi. 54, f. 17-21* j Type No. 362), plate 12, fig. 488^. Valves broadly lanceolate, with apices attenuate, showing a pseudo-raphe distinct and covered throughout its length with striae, 9 in 1 c.d.m., composed of coarse beads. Septa furnished with a single very large opening. Girdle face presenting a small number of false septa, appearing to alternate, and with margins furnished with coarse beads, 9 in 1 c.d.m. Length, 1 to 5 c.d.m. Breadth, 1-5 to 35 c.d.m. Marine. — Blankenberghe (H.V.H. ). England (Kitton, Comber, Norman, Stolt., W. Sm., Ralfs). Scotland (Hennedy). Ireland (O'Meara). All the coasts of the North Sea. _ J GENUS 72.-CLIMACOSIRA GRUN., 1862. The genus Climacosira only differs from Rhab- doncma by the septa showing numerous openings more or less irregularly scalariform. It includes but one species — CI. mirifica Gr. (K/iab- donema jninficum IF. Sm.) — found up to the present time living in Brazil, Honduras and Asia, and fossil in the Island of Nankoori. Figure 1 1 2 represents one of the characteristic septa. Fig. 112. Climacosira mirifica. 362 STRIATELLA. GENUS 73.— STRIATELLA AGARDH, 1832. Valves lanceolate or linear elliptic, furnished with a pseudo-raphe usually distinct, without costae ; striae excessively delicate. Girdle face showing a large number of false septa. Frustules very slightly silicious, longly stipitate. Endochrome granular, radiant around a central point. Fig. 113. — Striatella unipunctata. Fig. 114. Striatella delicatula. var. rectangulata. F'g- "5- Striatella interrupta. The genus Striatella, as at present constituted, results from the fusion of three former genera : — i. Striatella Ag. (fig. 113), septa continued throughout the girdle face of the frustule. 2. Hyalosira Kiitz. (fig. 114), septa appear- ing alternately, interrupted at their apex. 3. Tessella Ehr. (fig. 115), septa interrupted in the middle of their length. About a dozen species have been described, but only the following are found in the North Sea : — ANALYSIS OF SPECIES. f Septa continued throughout the length of the girdle face, size considerable S. unipunctata. -! Septa appearing ( Size small, septa scarcely visible . . S. delicatula. alternate, < L interrupted. (.Size medium, septa clearly visible . . . S. interrupta. STRIATELI.A. 363 S. delicatula (Kutz.) Grun. (Hyalosira delicaiula Xutz.,Bac, pi. 18, f. 3 (1), etc. j H.V.H. Atl., pi. 54, f. 5 and 6*; Type No. 357), plate 12, fig. 483,7. Valve elliptic lanceolate ; striae very fine, 36 in 1 c.d.m. Girdle face quadrangular, showing 4 to 5 pairs of septa, alternate, robust at the margin of the frustule, but becoming gradually slender. Length, about 1 c.d.m. ; breadth, up to 1*5 c.d.m. Marine. — Ostend (Westendorp in No. 797). Heligoland (Kutz.), and probably on all the coasts of the North Sea, where it is overlooked in consequence of its small size and delicate nature. S. interrupta (Ehr.) Heiberg. (Danske Diat, pi. 5, f. 15; H.V.H. Atl., pi. 54, f. 8* ; Type No. 358 ; Te'ssella interrupta Ehr.), plate 12, fig. 484^. Valve linear elliptic, with pseudo-raphe very distinct ; girdle face quad- rangular, with rounded angles, showing numerous false septa, alternate, clearly visible up to the middle of the length of the frustule, with intervals covered with delicate granules (22 in 1 c.d.m.) arranged in quincunx, and producing with oblique illumination the image of very approximate fine stria?. Length, about 3 c.d.m. Breadth, about 6 c.d.m. Marine. — Not yet found in Belgium. Flessingue (H.V.H.), England, Ireland, Germany, Heligoland, Bahnsie. S. unipunctata Agardh. (Kutz. Bac, pi, 18, f. 5 ; h.v.h. Atl., pi. 54, f. 9 and 10* ; Type No. 359), plate 12, fig. 485,7. Vaive broadly lanceolate, with pseudo-raphe very distinct, covered with very fine puncta, arranged in curved lines ; girdle face showing very numerous septa, extending throughout the length of the frustule, with intervals filled with fine puncta (more marked on the margin of the false septa), arranged in lines cutting one another at right angles, about 23 in 1 c.d.m. With oblique illumination these rows of beads assume the appearance of lines as in fig. 485 (right hand fig.). Figure 485 (left hand fig.) represents the appearance of lines which the rows of beads on the valve can assume. Length, about 6 to 8 c.d.m. Breadth, more than 10 c.d.m. Marine. — Not yet found in Belgium. Coasts of the North Sea: England (Kitton, Comber, Stolt), Ireland (W. Sm., O'Meara), France, Heligoland, Denmark, Bahnsie. 364 LAMELLA. B. Rudimentary false septa reduced to knobs. GENUS 74.— LAMELLA BRUN, 1894. Valves bacillar, dilated at the median portion and at the apices ; the latter with hyaline inflations. Girdle face showing bosses (false rudimentary septa ?) clearly displayed and very smooth. This genus has been proposed by Prof. Brun for a fossil form found in Totata, Oamaru, New Zealand, L. oculata Brun, which will be found represented in the text. Fig. 116. Lamella oculata. COHORT OF SURIRELLINE^E. Tribe XVI. — Surirelle^. Valves undulated transversely, undulations visible in the girdle face, striate, and showing several bands transversely shaded . . . Cymatopleura. ' Valve elliptic, sometimes constricted in the middle, fur- nished with a pseudo-raphe crossed at the median por- tion and longly bifurcated at the longitudinal apices . Hydrosilicon. f Valves cuneate, furnished with costae and beads; valves flat, without alas . Podocystis. Valves not transversely undulate. j Valves flat or spirally torsive, furnished Raphe not j with costas and moniliform striae, frus- bifurcate. tules alate . . . Surirella. Valves saddle-shaped, with pseudo-raphe arranged in the two valves in the form [_ of a cross . Campy lodiscus. z PODOCYSTIS. 365 GENUS 75.— PODOCYSTIS KUTZ, 1844. Valves cuneate, furnished with transverse costae and distinct pseudo-raphe. Frustules cuneate, stipi- tate, without obvious alae. Fig. 117. Po iocystis Adriatica, Podocystis Adriatica Kutz. (Baa, p. 62; h.v.h. Atl., pi. 55, f. 8*; Type No. 366), fig. 117 above. Valve cuneate, sometimes attenuate near the base, furnished with trans- verse costae and rather fine puncta, arranged in transverse and oblique rows. Marine.— Southern shores of England (W. Sm. , Roper), Ireland (O'Meara). This diatom belongs especially to the Mediterranean and Adriatic. Euphyllodium spathulatum Shadb. is also a Podocystis, but it cannot be considered as identical with P. Adriatica, as De Toni and other authors make it. The valves are furnished with a net work of transverse and longitudinal costae, anastomosed, thickened ; at the bottom of the cavities formed by this network is found a transverse costa, excessively delicate, and bearing on each margin a very minute beard. I therefore assign to this form the name of Podocystis spathulatum (Shadb.) H.V.H. The valve is similar in form to the preceding species. It inhabits the Islands of Ceylon, Nankoori, etc. It is, perhaps, identical with P. Australica Witt, which I only know from the description given by De Toni. In the latter case the name of Shadbolt should be retained, as the species of Witt dates from 1873, while that of Shadbolt was described in 1854. / 366 HYDROSILICON. III •I '1/ GENUS 76.— HYDROSILICON BRUN, 1891. Valve lamellar (sometimes pandu- riform), being transversely and longi- tudinally a pseudo-raphe, with simple or double bifurcations near the ex- treme curvatures of the valve. Bor- der thickened, striped, covered with a row of coarse beads. Striation having as centre of radiation, the axes of the crossing of the raphes (Brun). The genus includes two species, H. rimosa (CM.) Brun. ( ' Amphiprora rimosa CM earn) and H. mitt a Brun., which is represented in figure 118 in the text. To the description given by Professor Brun., it should be added, thai when seen in girdle view the H. mitra shows convex valves, strongly constricted at the median portion, and that the space comprised between the terminal bifurcations of the raphe is abruptly flattened. H. mitra inhabits the Indian Ocean, Australia, etc. Fig. 118. — Hydrosilicon mitra. §U*?M GENUS 77.— CYMATOPLEURA W. SMITH, 1851. Valves transversely undulate, finely striate, with pseudo-raphe distinct but inconspicuous. Girdle face show- ing the undulations of the valve. Fig. 119. Cymatopleura Solea. CYMATOPLEURA. 367 ANALYSIS OF SPECIES. Valves broadly elliptic or elliptic lanceolate . C. elliptica. Valves linear, with apices generally rostrate rj Solea C. elliptica (Breb.) W. Sm. (S.B.D., i., pi. 10, f. 80 ab; H.V.H. Atl., pi. 55, f. 1*), plate 12, fig. 480 b. Valve broadly elliptic or elliptic lanceolate, with margins furnished with short costse simulating coarse beads ; striae delicate, 18 in 1 c.d.m. Girdle face showing a small number of undulations. Length, 8 to 14 c.d.m. Fresh water. — Rather common throughout Europe. var. constricta Grun. (H.V.H. Atl-, pi. 55, f. 2*), plate 12, fig. 481 b. Valves longly elliptic, slightly constricted at the median portion. var. Hibernica. (C. Hibernica IV. Sm. ; H.V.H. Atl., pi. 55, f. 3-4*), plate 31, fig. 863. Valve broadly oval, with apices somewhat acuminate-rostrate. Fresh water.— Not yet found in Belgium. Ireland (W. Sm.), Scotland (Dickie), France (De Bntoison). C. Solea Breb.) W. Sm. (S.B.D., i., pi. 10, f. 78; H.V.H. Atl., pi. 55, f. 5-7*), plate 12, fig. 482 £. Valves more or less longly linear, with apices generally rostrate, median portion constricted, margins furnished with somewhat longer costte than in the preceding species, and showing coarse moniliform striae, about 6 in r c.d.m. In very oblique illumination the striation shown in fig. 482 (left-hand figure) may be seen. Girdle face very narrow, and showing a large number of undulations, sometimes opposite, sometimes alternate. Length, 5 to 13 c.d.m. Fresh water. — Rather common throughout Europe. var. regula (Ehr.) Ralfs. Valve with parallel margins, not constricted in the median portion. 368 SURIRELLA. GENUS 78.— SURIRELLA TURPIN, 1827. Valves cuneate, reniform, elliptic or linear, sometimes twisted, having a pseudo-raphe linear or lanceolate ; furnished with costse, short or reaching to the pseudo-raphe, and a submarginal keel of greater or less size ; pseudo-raphe parallel in the two valves. Girdle face showing alae produced on the projecting keel. Fig. 120. — Surirella biseriata. Endochrome formed of two layers, each of which rest flat about the middle, on the interior side of the valves. SURIRELLA. 369 ANALYSIS OF SPECIES. a! > Valves showing robust costse throughout their length and reaching to the median line. f Valve small, linear or ellip- The two apices equally conical. tic Valve late very large, lanceo- I Valve of medium size, lan- ceolate, constricted at middle Valve oval , one apex acute, the other obtuse I Striae not reaching to the pseudo- raphe ;si?e very considerable Striae reach- ing to the pseudo raphe. Costa leaving no space free except a very narrow pseudo-raphe. Size very small, striae robust Size very large, strife fine . S. linearis. S. biseriata. S. Smithii. S. elegans. subsala Gemma. s I t Costa: leaving near the pseudo- raphe a rather broad striated space. I Valve longly oval ; alas very robust, more or less approximate to the connecting zone. S. robusta. I V I rive broadly oval ; alas conspicuous, quite marginal S. striatula. I Costa- marginal or becoming more feeble near the centre of the valve. Costa- very robust on the margin of the valves, becoming more feeble near the median portion. Marine species, very robust . . . . . S. fastuosa. As the preceding, but costre leaving a lanceolate blank space. Fresh and brackish water . . S. turgida Costa: marginal or becoming very delicate near the central portion of the valve. Fresh or brackish water species. Rather delicate . . . S. ovalis. [ Valves twisted round the pseudo-raphe. Frustule in form of figure 8 S spiralis. /. Valves plain. A. Valves showing robust costae throughout their length, and reaching to the median line. ,7. THE TWO Al'ICES OF THE VALVE EQUALLY CONICAL. S. biseriata Breb. (Aig. Falaise, pi. 7 ; h.v.h., pi. 72, f. j to 3*; Type Nos. 420, 421), plate 12, fig. 575. Valve broadly lanceolate, with apices sometimes somewhat sub-rostrate, sub-obtuse, with costae robust, the median straight, the terminal radiant. Pseudo-raphe with hyaline area of more or less breadth, and more or less lanceolate. Striae very delicate. Girdle face linear, oblong, with rounded angles, showing the keel alate, robust. Length, 10 to 17 c.d.m. Fresh water. — Rather common throughout Europe. A A 370 SURIRELLA. var. amphioxys. (S. amphioxys IV. Sm.). Very small ; with valves linear, apices cuneate, more or less acuminate rostrate. Fresli water. — France (De Brdb.), England (Carrington, Okeden), Aboyne, Scotland (Baxter Coll., 2920), Ireland (Arnott in Baxter Coll., 2817). S. linearis W. Sm. (S.B.D., i., p. 31, pi. 8, f. 58a*), plate 31, fig. 864. Differs from S. biseriata, of which it is probably only a variety, by its smaller and narrower valves and apices equally rounded, sub-obtuse. Fresh water. — Belgium (not yet found), England (Kitton, Comber, Norman), Scotland (Dickie), Ireland (O'Meara). S. Smithii Ralfs (in Pritch. Inf., p. 794 ; 6". constricta IV. Sm. ! ; S.B.D., i, p. 31, pi. 8, f. 59*), plate 31, fig. 865. Valves lanceolate, with apices cuneate, slightly obtuse, often constricted at the median portion ; costas delicate, about 4-5 in 1 c.d.m. Pseudo-raphe narrow, linear in the constricted valves ; lanceolate in the valves not con- stricted. Girdle face linear, with apices truncate, angles rounded, alae very conspicuous. Length, 7 to 14 c.d.m. Brackish water.— England (W. Sm. ! Comber, Stolt.), Ireland (O'Menra). a a. VALVE OVAL, ONE OF THE APICES MOKE OK LESS ACUTE, THE OTHER OBTUSE. S. elegans Ehr. (Verb., p. r36, pi. III., i, f. 22; h.v.h. Atl., pi. 71, f. 3*; Type No. 419), plate 12, fig. 576. Valve more or less broadly oval, very large, with median line narrow, surrounded by a hyaline area, lanceolate, broad, with rather strong costse, about 1 "5 in 1 c.d.m. ; striae fine, excessively delicate, 22 in 1 c.d.m. Girdle face cuneate, with apices obtuse, rounded ; alae rather robust, very approxi- mate to the margin. Length, 18 to 22 c.d.m. Fresh water.— Brussels (Del.), Aid. Lieg. (De Wild.), Devizes, England (Baxter Coll., 2683), Hull (Norman), Ireland (O'Meara), Loch Kinnord, Scotland (Temp, and Per., No. 4), Elgin, Scotland (Arnott in Baxter Coll., 2820). S. subsalsa W. Sm. ! (S.B.D., i., p. 34, pi. 31, f. 259*), plate 31, fig. 866. Resembles considerably a miniature or reduced form of S. Splendida. Valves very small, more or less broadly oboval, with costag rather robust, 3 in SURIRELLA. 37 1 i c.d.m. Pseudo-raphe very narrow; stria? rather strong, 10 or 1 1 in i c.d.m. Girdle face linear, somewhat cuneate, with alee very conspicuous. Length, 1 5 to 4 c.d m. Brackish water. — England (W. Sm. ! Kitton, Norman, Greg.). S. robusta Ehr. (Mb., 1840, p. ^15; Mikr., pi. 15, f. 43: Suri- rella nobilis IV. Sm. ; H.V.H. Atl., pi. 71, f. 1 and 2* ; Type 4(8), plate 12, fig- 577 Differs from the preceding by its more considerable size, the absence of a hyaline area round the median line, the more robust costa?, the better marked stria?, and by the ahe being approximate to the connecting zone. Fresh water. — Aid. Lieg, (De Wild.). It is found here and there in Europe. var. splendida. (Nov.? spkndida Ehr., Inf. pi. 14, f. 1 ; S. splendtda Kiitz., H.V.H. Atl., pi. 72, f. 4*; Type No. 422), plate 12, fig. 578. Distinguished from the type-form by its smaller dimensions and longer costa;, still more approximate to the median line. Fresh water. — Rather frequent everywhere. S. Cafironi Breb. ! is only an anomalous form of the preceding variety. It is characterised by a ridge at the inferior apex of the r?phe, and result ing from a prolongation of the costa?. This form is found occasionally mixed with the type-form. var. tenera. (S. tencra Greg.; in H.V.H. Type No. 62, rare), plate 12, fig. 579. Differs from the preceding by its narrower form and less marked ala?. Fresh water.— Frahan (Del.), Scotland (Greg.). S. Striatula Turpin (Mem. du Mus. d'Histoire Nat., XVI. ; H.V.H. Atl, pi. 72, f. 5* ; Type No. 423), plate 13, fig. 580. Valve broadly oval, with costa? robust, distant, about 1 in r c.d.m., reach- ing to the median line ; stria? rather visible, about 14 in 1 c.d.m. Girdle face very cuneate, showing not very robust ala?, quite marginal. Length, 10 to 16 c.d.m. Marine and brackish water. — Hlankenberghe, Antwerp (Scheldt), England (Kitton, Comber, Stolt., Norm.), Ireland (O'Meara), and on all our coasts. var. biplicata Grun. (H.V.H. Atl., pi. 72, f. 6*), plate 13, fig. 581. Showing a longitudinal plica near the median portion. Antwerp (Scheldt. P. Gaut. ). Very rare. 372 SURIRELLA. S. Gemma Ehr. (Abh., 1840, p. 76, pi. 4, f. 5; H.v.H. Atl., pi. 74, f. 1-3* ; Type No. 433), plate 13, fig. 582. Valve more or less longly oval, with costae indistinct, about 2 to 3 in 1 c.d m., reaching to the median line, which is narrow ; strice fine, transverse, 20 or 21 in 1 c.d.m., resolvable into beads in appropriate illumination. Girdle face strongly cuneate, alae marginal, scarcely visible. Length, about 7 to 12 c.d.m. Marine. — Blankenberghe, Antwerp (Scheldt, H.V.H.) Common on all our coasts. A A. Costae marginal or becoming gradually fainter. a. COSTAE VERY ROBUST ON THE MARGIN OF THE VALVES. S. fastuosa Ehr. (Abh, 1S41, p. 19; h.v.h. Atl., pi. 73, f. 18*; Type No. 432), plate 13, fig. 583. Valves broadly oval ; costse very robust at the margin, but gently diminish- ing in breadth as far as the third of the valve where they leave a space lanceolate, bordered with elongated dots, and sometimes they continue in this space, but in doing so they become more delicate. Pseudo-raphe narrow. Striae delicate, about 19 in 1 c.d.m. Girdle face cuneate, with rounded margins, showing robust alas, approximate to the connecting zone. Length, 5 to 12 c.d.m. Marine.— Washings of mussels (Deby), Blankenberghe, Scheldt. (H.V.H. ), England (W. Sm, Comber, Norman, Stolt,), Ireland (O'Meara), Scotland (Arnott in Baxter Coll. 2546, 2764). Very numerous forms there as well as on all our shores. var. lata. (S. lata IV. Sm.; H.V.H. Atl, pi. 73, f.17*), plate 13, fig- 584- Differs from the type-form by its larger size, and by the median con- striction of the valves. With the preceding. —Scheldt (H.V.H.), England (Comber, Ralfs.), Scotland (William- son), France (Breb.), The innumerable forms of S. lata have been raised by some authors to the rank of species. Gregory has further recorded intermediate forms, which connect S. fastuosa with S. lata. S. turgida W. Sm. (S.B.D,i,p.3i,pi.9,f. 60*), plate 31, fig. 867. Valve elliptic, oval, with apices sub-obtuse or slightly acute ; median portion much inflated; costoe robust, shortened, about 1-25 in 1 c.d.m.; pseudo-raphe much enlarged, lanceolate. Length, 7 to 12 c.d.m. Fresh and brackish water. — England (Norman, Carrington), Ireland (Dickie). SURIRELLA. 373 a a. COST.E MARGINAL, OR VERY DELICATE AT THE MIDDLE OF THE VALVE S. ovalis Breb. (Kiitz. Baa, p. 61, pi. 30, f. 64; H.V.H. Atl., pi. 73, f. 2* ; Type No. 425), plate 13, fig. 585. Valve oval elliptic or ovate, with costa? marginal, short, narrow, 5 in 1 c.d.m. Pseudo-raphe narrow. Striae rather delicate, 18 in 1 c.d.m. Girdle face slightly cuneate, with alas indistinct. Length, 5 to 8 c.d.m. Fresh and brackish water. — Brussels (Del.), Antwerp. Found everywhere. var. Crumena. (S. Crumena Breb./; H.V.H. Atl., pi. 73, f. 1*; Type No. 424), plate 13, fig. 586. Valve almost disciform. Pseudo-raphe very narrow. Fresh and brackish water. — Antwerp, common in the Scheldt. La Hulpe, Brabant (Del.). England (Comber, Norman, Stolt.), Scotland (Arnott. in Baxter Coll. 2686), Ireland (O'Meara). var. ovata. (S. ovata Kiitz. ; H.V.H. Atl, pi. 73, t. 5-7*; Type No. 426), plate 13, fig. 587. Smaller than the type-form (4 to 5 c.d.m.), and quite ovate. In a form from the Scheldt (fig. 587, two right-hand figures), the costae are prolonged up to the median line, while becoming gentlv thinner. Same stations. — Rather common. var. minuta. (S. minula Breb. ; H.V.H. Atl., pi. 73, f. 9-14* ; Type No. 428), plate 13, fig. 588. Still smaller than the preceding variety (2 to 3 c.d.m. in length), and more elongated, with costae generally delicately prolonged as far as the median line. Same stations. var. salina. (S. salina IV. Sm. : H.V.H. Atl., pi. 73, f. 15*; Type No. 431), plate 13, fig. 589. Valves oval elliptic ; costae 5 or 6 in 1 c.d.m. Brackish water. — Antwerp, in the Scheldt. England (W. Sm.). var. angusta. (S.angusta Kuiz. : H.V.H. Atl., pi. 73, f. 12*; in Type No. 430), plate 13, fig. 590. Valve very narrowly oval, linear, or sometimes panduriform, with rounded apices. Length, 3 to 5 c.d.m. Fresh water. — Koekelberg (Del), Aid. Lieg. (De Wild.) var. pinnata. (S. Pinna/a W. Sm. ; H.V.H. Atl., pi. 73, f. 13*; Type No. 429), plate 13, fig. 591. Valve linear, narrow, with apices cuneate. Mean length, 4 to 5 c.d.m. Fresh water. — Laeken (Del.), England (W. Sm., Arnott in Baxter Coll., 2793). All these forms, which are connected with one another, cannot be specifi- cally separated. 374 SURIRELLA. II. Valves twisted, raphes of the two valves parallel. S. spiralis Klltz. (Baa, pi. 3, f. 64 ; Campylodiscus spiralis IV. Sm. ; S.B.D., i., p. 29, pi. 7, f. 54; S. flexuosa E/ir., Amer., 1843. p. 136, pi. J. 3, f. 1-20; S. torta Breb. ; H.V.H. Atl., pi. 74, f. 4-7 * ; Type No. 434), plate 13, fig. 592. Valve elliptic lanceolate, twisted round the longitudinal axis ; costa; robust, 2 to 3 in 1 c.d.m., reaching close to the median line ; striae fine, but well marked, about 26 to 28 in 1 c.d.m.; here and there throughout the length of the costre some coarse scattered puncta. Frustule twisted into a figure of 8, with connecting zone rather broad, showing the aire distinctly, with raphes parallel and superposed on the two valves. Length, 10 to 13 c.d.m. Freshwater. — Rather rare: Dieghem (Del.), Antwerp. England (W. Sm., Kitton in Baxter Coll., 3507), Ireland (O'Meara), France (Br£b.), etc. By the side of Surirella are placed the two following genera, which have not been generally adopted. Stenopterobia De Breb. in litteris. Frustules very elongated and very narrow, sometimes sigmoid. In this are comprised the Surirella Baileyi Lew., S. intermedia Lew., S. delicatissima Lew., and S. anceps Lew., which appears to be a Synedra furnished with coarse marginal sparse puncta. These four forms are American, and are figured by Lewis in " On some new and singular intermediate forms of Diatomacea." The S. anceps Breb. is found in Type No. 291, which is said to have come from Cornouailles. Plagiodiscus Grun. and Eul., 1868. Valves reniform with radiant costas, includes two forms, Plagiodiscus nervatus Grun., and PL Martensianus Grun. These are abnormal forms of a Surirella, closely allied to, if not identical with, S. Gemma. CAMPVLODISCUS. GENUS 79.— CAMPYLODISCUS EHR, 1841. 375 ■, -. v-^. ^c-^ <». ^. _•»„.„ . „ . , o » ,, «# ,», , // .safe H»5s*> fe£3*""" Jl o o ■ ff ■ '» —^T^**: e « a < o J 0 / A-*' - ——- -& •-"•*t- y ■<■-£:? 9 o, t L's---** ' 0 fl ' 0 _.*> »' P «*„«»' a? ' . •'!' « sg§ ^ t-^'V^v •V £*!Ss € / / ^ it ft V ^ .yife 'l,H W/M Mim Fig. 122. ( 'ampylodiscus parvulus. Fig. T2i. — Campylodiscus Clypeus. Valves circular, furnished with costal usually short. Frustules saddle-shaped, with the median lines of the two valves thrown across one another at right angles. The valve is perfectly circular, but it appears to be irregularly circular in conse- quence of its curvature. Endochrome as in the Surirella. This genus was in great confusion, but Mr. J. Deby has set it in order by the publication of his Prelude to a Monograph, under the title of " An 376 CAMPYLODISCUS. Analysis of the Diatomaceous Genus Campylodiscus," London, 1891. Mr. Deby admits 92 species into the genus, and divides them into 5 sections, as follows :— (1.), The Raphidaa ; (11,), the Vagae ; (in.), the Hyalinse ; (iv.), the Striatae; and (v.), the Punctata?. We shall adopt Mr. Deby's sections and analysis. SECTION I. Raphidce. — Valves furnished with a narrow hyaline space, or longitudinal line (Raphe). f Area limited internally by a distinct line, being the termination of the costae ; discs without a trapezoidal inscribed line . . . C. Hodgsonii. • r •. j 1 f Raphe reduced to a mathematical line . . C. Ralfsii. Area not limited by ' Raphe enlarged, distinct. , . C decorus. C. Hodgsonii W. Sm. (S.B.D., i., p. 29, pi. 6, f. 53* ; Deby, pi. 1, f. 7) plate 32, fig. 868. Valve appearing irregularly circular, furnished with a crown of radiant costae, short, confluent on the interior side in a circular line ; costae 3 or 3-5 in 1 c.d.m. Median hyaline space, narrow, lanceolate, bordered on each side by transverse rows of coarse beads. Diameter, about 18 c.d.m. Marine. — England (Hodgson, Norman, W. Sm.), Ireland (O'Meara), France (Brebisson). C. Ralfsii W. Sm. (S.B.D., i., p. 30, pi. 30, f. 257, ; Deby, pi. 2, f. 18*). plate 32, fig. 869. Valve small, almost regularly circular, showing narrow costae extending up to the raphe, which appears in the form of a mathematical line. Costae on the margin of the valve, 4 in 1 c.d.m. Diameter, 4 to 4'8 c.d.m. Marine. — England (W. Sm., Kitton), Ireland (O'Meara), Coasts of France (Brebisson), Bahnsie (Eagerstedt). C. decorus Breb. (Diat. Cherb., f. 2 ; h.v.h. Atl., pi. 75, f. 3*), plate 14, fig. 596. Differs from C. Ralfsii by the rather broad median area and by its size, which is larger. Marine. — Escant (H.V.H.), England, (Norman). forma minima ? (H.V.H. Atl., pi. 77, f. 2*), plate 14, fig. 597. Under the name of C. parvulus. Antwerp (Scheldt). CAMPYLODISCUS. 377 Section II. Vagce. — Area vaguely limited in consequence of the absence of the rays. i Valves with very small puncta, forming short lines, interrupted by a hyaline circle . . . . . E. Echeneis. (Valves with very coarse puncta, forming continued radial lines . . E. Clypeus. C. Echeneis Ehr. {Coronia Echeneis Ehr.,V>tx., 1841 ; C.cribrosus W. Sm., Deby, pi. 9, f. 50 ; H.V.H. Atl., pi. 76, f. 1 and 2* ; Type No. 437), plate 14, fig. 600. Valve appearing irregularly circular, with cost?e scarcely noticeable at margin, replaced over the remainder of their length by rows of elongated coarse beads, very variable in number. Pseudo-raphj in the form of a blank space of greater or less breadth. Diameter, 8 to 14 c.d.m. Fresh and brackish water.— Washings of mussels (Deby), Antwerp (Scheldt), Blankenberghe (H.V.H). Very rare. France. Bahnsie. England (Brightwell, W. Sm., Comber, Stolt., Norm.), Ireland (O'Meara). C. Clypeus Ehr. (Mikr. pi. 10, f. I. i ; Deby pi. 9, f. 49 ; H.V.H. Atl., pi. 75, f. 1*, Type 435), plate 14. fig. 598. Valve very large, regularly circular, with costre (1-5 in 1 c.d.m.) occupying only about the moiety of the ray, interrupted on the two sides by a very broad sulcus (inflexion of the valve). Central portion of the valve occupied by coarse puncta arranged irregularly, inteirupted by a rather broad pseudo raphe and circumscribed by a second broad depression of the valve. Inter- costal stria?, 21 in 1 c.d.m., formed of elongated puncta, and accompanied by coarse puncta arranged throughout the entire length of the costae. Diameter, about 20 c.d.m. Brackish water. — Ostend (Grunow), Heyst (Deby), Antwerp (Scheldt), Blankenberghe (H.V.H.), England (Wighani, Okeden), frequent. Cuxhaven, Bremershaven. Section III. Hyalines. — Valve with a large, smooth, hyaline central area, without any puncta. C Hyaline area limited by a circlet of puncta, narrow portion Rays in- (stem) of rays often longer than the broader portion fundibuli- (funnel) . C. Horologium. form . I Hyaline area not limited by a circlet of puncta, intercostal spaces smooth . . C. latus. I Rays not infundibuliform ; hyaline area elliptic, with acute apices ; rays not originating in a single very coarse bead . . . • C. annularis. C. Horologium Williams (in Ann. and Mag. of Nat. Hist., 1848, Deby, plate 6, f. 29a*), plate 32, fig. 870. 378 CAMPYLODISCUS. Valve large, orbicular, with external margin broad, traversed by numerous fine costa?, shortened ; costae infundibuliform, narrow portion (stem) of funnel often (not always) shorter than the broader portion, the latter showing rows of fine beads. Median area smooth, limited by a row of fine short lines, and by the confluent apices of the costae. Diameter, 12 to 16 c.d.m. Marine. — Coasts of England and Scotland ; in Loch Fine (Greg. !). C. latUS Shadb. (in T.M.S., 1854, ii., p. 16, pi. 1, f. 13; Deby, pi. 3, f. 30/;*), plate 32, fig. 871. Differs from the preceding by its smaller size, by the broader portion of the funnel being much longer than the narrow portion, and by the absence of an internal circlet of puncta and of confluent apices of the costae. Diameter, 5 to 7 c.d.m. Marine. — Coasts of Scotland (Greville). C. angularis Greg. (Diat. of Clyde, p. 30, pi. 3, f. 53; Ad. Schm. Atl., pi. 18, f. 7* ; Deby Campyl, pi. 3, f. 22), plate 35, fig 909. Valve orbicular, of medium size ; costae not infundibuliform, very broad at the margin, gently diminishing, apparently genuflexed (and appearing to alternate with some shorter costae), radiant, about 5 in 1 c.d.m., leaving in the middle of the valve an oval, broad, acuminate area. Diameter of valve, 5 to 9 c.d.m. Marine. — Coasts of Scotland (Gregory). Bahusie (Lagerst). Section IV. Striata. — Median area bearing distinct striae. Valve appearing more or less cordate, with median area smooth, limited by short lines ; rays funnel-shaped, with the widened portion very broad C. Thuretii. Valve appearing almost round, with median portion sub-quadrangular, showing a second row of costae, separated from the first by a sulcus . C. bicostatus. C. Thuretii Breb. (Diat. Cherb., pi. i, f. 3; h.v.h., pi. 77, f. 1* ; Types Nos. 438 and 439), plate 14, fig. 595. Valve appearing irregularly circular or broadly ovoid, with coarse robust costae, 2 to 3 in 1 c.d.m., becoming abruptly narrower near the central portion of the valve, which is covered with delicate transverse striae, about 10 in 1 c.d.m., interrupted by the pseudo-raphe on each side, at a short distance from the latter, by a sulcus parallel to it. General appearance of the valve smaller to that of Surirella fastuosa. Diameter, about 5 c.d.m. Marine. — Rare. Blankenberghe. Washings of mussels (Debv), Coasts of England (W. Sm., Gregory), France (Br6b. Thuret,), Bahnsie (Lagerstedt). CAMPYLODISCUS. 379 C. bicOStatUS W. Sm. (S.B.D., ii., p. 88; Deby, pi. 7, f. 38a; H.V.H. Atl, pi. 75, f. 2*), plate 14, fig. 599. Valve appearing almost round, with narrow costa?, the intervals of which are punctate ; median area subquadrangular with rounded angles, showing a second row of costa? separated from the first by a smooth space. Diameter 3"5 to 5 '5 c-d-m- Marine. — Blankenberghe, Antwerp (Scheldt. H.Y. H.), England (Roper, Kitton, Norman, etc.), Ireland (O'Meara), France (Br£b.). In spite of the opinion of our late friend Mr. Deby, we think that the figure in our Atlas represents faithfully the C. bicostatus of W. Sm. when viewed with an objective of superior quality. The figure was drawn from examples from our Type No. 436 (coming from Africa). Our gatherings from the Scheldt are intermediate in form between Professor Smith's figure and our own. Section V. Punctata. — Median area punctate or punctato-striate. f Valves without ( Rays from 40 to 60 in number . . C. Hibernicus intercostal < apiculi. ( Rays from 90 to 100 in number . . C. Noricus. f Median area angular at its two apices and strongly ,, , ■ . punctate; rays very numerous, commencing with vaives witti . a bead _ C. eximius intercostal aPlc ■' Median area elliptic, with rounded apices, provided with fine puncta near the costre ; rays contiguous C. limbatus. C. Hibernicus Ehr. (Mik., pi. 15A, f. 9; C. cosiatus W. Sm. ; H.V.H. Atl., pi. 77, f- 3*; Type No. 440), plate 14, fig. 593. Valve appearing irregularly circular, furnished with costa? (1*5 to 2 in 1 c.d.m.), very robust at the margin but becoming gradually thinner near the central portion of the valve, where they leave a subquadrangular punctate space ; stria? fine, intercostal, accompanied by coarse dots, scattered through- out the length of the costs. Frustule very curved ; connecting zone rather broad, bordered with coarse areola?, produced by the commencement of the costa?. Diameter, about 10 c.d.m. Freshwater. — Rather rare and not abundant ; Louvain (P. Gaut. ) ; Antwerp; England (W. Sm.) ; Ireland (O'Meara). var. Noricus. (C. Noricus Ehr. ; H.V.H. Atl., pi. 77, f. 4-6* ; Type No. 441), plate 14, fig. 594. Costa? more approximate (2 to 3 in 1 c.d.m.) than the type-form. Fresh water. — Rare. Rouge-Cloltre (Delogne). England (W. Sm.). C. eximius Greg. (Diat. of Clyde, p. 31, pi. 3, f. 54; Deby., pi. 10, f. 61*), plate 32, fig. 872. 38o HANTZSCHIA. Valve suborbicular, with margin showing narrow costal, approximate, commencing with a bead and about 160 in number in a valve (about 5 in 1 c.d.m) ; median area covered with a delicate network and showing a narrow pseudo-raphe. Diameter, 7 to 1 2 c.d.m. Marine. — Scotland (Gregory) ; France ! C. HmbatUS Breb. (Diat. Cherb., p. 12, f. 1 ; Deby., pi. 10, f. 62* ; plate 32, fig. 873. Valve orbicular, with a circlet of costs, very short, approximate, of almost equal thickness throughout their length, 3 in 1 c.d.m., and showing in each interval two rows of fine puncta ; median area almost smooth at the central portion, with margin showing 3 or 4 rows of fine puncta, concentric. Marine. — Coasts of Scotland and of France, and probaby in other portions of the North Sea. COHORT IV.-NITZSCHIINE^. TRIBE XVIL— NITZSCHIE^;. f 1 Keel diagonally opposite in the two valves . Nitzschia. j r rustules free. -, j^ee] 0f tne two vaives placed on the same side of '. ( the frustule .... Hantzschia. [_ Frustules enclosed in mucous sheaths .... Homceocladia. GENUS 80. — HANTZSCHIA GRUNOW, 1877. Valves arcuate, with rostrate apices, fur- nished with a keel having short dots, pro- longed into short costae, or traversing the entire valve ; between the two median dots is found the rudiments of a nodule. Girdle face showing keels placed on the same side of the frustule. Fig. 123. Hantzschia ampfiioxy: HANT2SCHIA. $&l ANALYSIS OF SPECIES. f Carinal dots prolonged into costte, which traverse the entire valve . H. marina. Carinal dots ( Carinal dots slightly prolonged . . H. virgata. slightly or not < prolonged. ( Carinal dots not prolonged . . . H. amphioxys. H. amphioxys (Ehr. ) Grun. (Arct. Diat, p. 103; Nitzschia amphioxys, IV. Sm., S.B.D., L, p. 41. pi. 13, f. 105 ; H.V. H. Atl., pi. 56, f. 1 and 2*; Type No. 367), plate 15, fig. 483/'. Valves feebly arcuate, with apices more or less prolonged. Keel with coarse short dots, about 7 in 1 c.d.m., the two median distant. Striae about 16 in 1 c.d.m. Length (very variable), about 4*5 or 7-5 c.d.m. Fresh and brackish water — Frequent. England (Kitton, W. Sm., Norman). Ireland (O'Meara). var. major. (H.V.H. Atl., pi. 56, f. 3 and 11*), plate 15, fig. 484/'. Much larger, about 12 c.d.m., with 5 to 6 carinal dots, and about 11 striae in 1 c.d.m. var. intermedia. (H.V.H. At!., pi. 56, f. 4*), plate 15. fig. 485/;. Pfean length, about 8 c.d.m., with 4 carinal dots, and about 11 striae in 1 c.d.m. var. vivax. (Nifzschi'i vivax Hanizscli non IV. Sm. ; H.V.H. Atl., pi. 56, f. 5 and 6*; Type No. 368), plate 15, fig. 486/;. Valve slender, longly rostrate ; about 5 carinal dots and 13 striae in 1 c.d.m. Length, 10 c.d.m. Brackish water. — England (Kitton). var. elongata. (H.V.H. Atl., pi. 56, f. 7 and 8*), plate 15, fig. 487/-. Length, up to 22 c.d.m.; strongly rostrate and genufiexed ; 7 or 8 carinal dots, and 17 striae in 1 c.d.m. H. virgata (Roper) Grun.! (Arct. D., p. 104; H.V.H. Atl., pi. 56, f. 12 and 1 3* ; Type No. 370), plate 15, fig. 488/'. Valve robust, arcuate, with apices strongly rostrate, rostrum obtuse > Keel with 4 or 5 dots in 1 c.d.m., dots prolonged into short costae on the valve. Striae, 9 to 11 in 1 c.d.m. Length, about 13 c.d.m. Marine. —Blankenbcrghe (H.V.H.), washings of mussels (Deby.), France (Breb.), England (Roper, Kitton, Comber, Stolt, Norman), Ireland (O'Meara). 382 NITZSCH1A. H. marina (Donkin) Grun ! (Arct. D., p. 105. Epithemia marina Donkin ; H.V.H. Atl., pi. 56, f. 14 and 15* ; Type No. 369), plate 15, fig. 489^. Valve arcuate, with rostrate apices. Keel with 6 dots in 1 c.d.m., prolonged into delicate costae, which traverse the entire valve, and between each of which are found two rows of fine alternating puncta. Girdle face linear, showing two keels inflected towards the connecting zone. Length, about 6 to 10 c.d.m. Marine. — Ostend, Blankenberghe (H.V.H), England (Donkin, Comber, Kitton), France (Br6b), Ireland (O'Meara). GENUS 81. NITZSCHIA (HASSALL, 1845; W. SMITH) GRUNOW Ch. em., 1880. Valves furnished with a keel, with carinal dots either short, or prolonged into short cost;e, rarely traversing the entire valve. Keels of the two valves diagonally opposite. Frus- tules free, rarely enclosed in tubes or united into a stratum. Endochrome consisting of a single lamina, interrupted partially or entirely at the median portion of the frustule. In the classification of this genus I shall follow the excellent monograph published by Mr. Grunow in the Arctische Diatomcen, and I have also borrowed from him a few of his descriptions. crr« Fig. 124. Nitzschia spectabilis. NITZSCH1A. )83 Table of Groups. f Striae in quincunx ; valve broad, constricted at the median portion 4; , bfl i C o ( s. L Valve f showing undula- -\ tions or hollows. [_ r Valve linear, longly lanceolate or longly elliptic ; striae very distinct Valve very broadly lanceolate ; transverse stria- very fine and indistinct Valves showing costre more or less dimidiate or carinal dots prolonged into delicate costrv. o 5'5 5 S J) m 3 if *- Si m zj 3 ^- Keel ! straight, not inflected at the median portion. \ Costae dimidiate, robust I ( Frustules straight I Costae ) I delicate. J Frustules spathulate or somewhat sig- V moid . f Keel almost central ; girdle face with apices not attenuate ..... Keel eccentric ; girdle face with apices very slightly I. attenuate . . . • Valve not undulated. Keel eccentric, inflected at the median portion I Valves arcuate . . . . . Keel accompanied by two longitudinal parallel lines ' Girdle f face J Keel eccentric ; girdle face not broad -a '5 E to 2. *Panduriformes. 1. Tryblionella. 5. Circumsutse. 9. Grunowia. 10. Scalares. 11. Insignes. 1G. Sigmoideae 17. Sigmata. 18. Obtusse. 19. Spectabiles. 14. Spathulatae. con- stricted in the middle. 6. Dubise. i Keel slightly eccentric; girdle face very broad 7. Bilobatse. f Carinal dots somewhat prolonged 13. Vivaces. 0 ' n c Q 4-* 0 3 > O ri xs Girdle face not con- stricttvl in the median portion. Valves showing a longitudinal sulcus in which the striae are absent or feeblv marked 3. Apiculatse. to S. o _ { Keel quite eccentric Keel almost central ; striae very distinct ; frustules uni- ted into a stratum o Hi 21. Lanceolatse. U I I 12. Bacillaria. 3 I 2 - to ;r _5 c Z u I -J, I Keel some- what eccentric ; frustules .j y^y(S lanceQ not united into strata. Valves linear, lirge ; striae distinct . 20. Lineares. I I Valve very longly rostrate and with a very eccentric keel late, very small ; striae indistinct . 15. Dissipatse. 22. Nitzschiella. * The figures correspond with those of the groups in H.V.H. Atlas; the missing numbers (4. Pseudo-Tryblionella and 8. Epithemioideae) are those of groups which are not represented in Belgium or England. 384 TRYBUONELLA. Group i. — Tryblionella (W. Smith partimj Grunow. Fig. 125. Nitzschia punctata ( Tryblionella). Keel very eccentric, with dots almost always indistinct, generally equal in number to those of the striae. Valves generally sulcate, undulate. I unite with this group, group 4 (Psenrfo- Tryblionella), which is only distinguished from it because the carinal dots are well marked. ANALYSIS OF SPECIES. { Valve showing strife formed of coarse puncta . N. punctata Valves not with coarse puncta. f Valves with strife very fine at the centre of the valve ; stria; terminating at the margins in a double row of puncta . N. navicularis. (' Stria; traversing the entire linear valve . N. angustata. Stria; Valve f Valves with robust stria; ; sul- not showing cus not hyaline . . N. Tryblionella. as above. a median | Valve very small ; stria- very ^ sulcus. (_ delicate; sulcus hyaline . N. debilis. N. navicularis (Breb.) Grun. ! (Arct. Diat., p. 67 ; H.V.H- Atl., pi. 57, f. 1* ; Type No. 371), plate 15, fig. 490. Valves elliptic-lanceolate, with striae (7 in 1 c.d.m.), fine at the central portion of the valve, terminating towards the margins on each side in a double row of puncta. Length, about 3*5 c.d.m. Marine. — Ostend (Deby.) ; Scheldt at Antwerp (H.V.H.) ; England (Norm., W. Sm., Comber, Dickie) ; France (Br6b.). N. punctata (Sm.) Grun. ! (Arct. Diat., p. 68; H.V.H. Atl., pi. 57, f. 2* ; Type No. 372), plate 15, fig. 491. Valve elliptic-lanceolate, with apices somewhat rostrate ; striae 7 to 9 in 1 c.d.m., formed of coarse puncta. Length of valve, 2*5 to 3^5 c.d.m. Breadth, 1 to 3 c.d.m. Brackish water. — Ostend (Deby); Antwerp; England (\V. Sm., Stolt., Comber) Holland ; Denmark. France NITZSCHIA. 385 var. elongata Grun. (H.V.H. At!., pi. 57, f. 3*), plate 15, fig. 492. Valves linear, with cuneate apices ; striae 5 or 6 in 1 c.d.m. Length of valves, 6 to 1 1 c.d.m. Breadth, 2 to 2-5 c.d.m. Marine. — Mixed with the type-form. — Ostend (Deby.). N. Tryblionella HantzSCh (Trybliondla Hantzschiana Grun. . H.V.H. Atl., pi. 57, f. 9, 10 and 15* ; Type No. 375), plate 15, fig. 493. Valve elliptic-lanceolate, with subacute apices, showing a broad con- spicuous sulcus; striae robust, 5 to 7 in 1 c.d.m., between which appear stria?, fine, delicately punctate. Length, 8 to 1 1 c.d.m. Breadth, 2 to 3 c.d.m. Fresh and brackish water — Not yet found in Belgium. England (Stolt.). Ireland (O'Meara). var. Levidensis. (T. Levidensis W. Sm. ; H.V.H Atl., pi. 57, f. 15 ; Type No. 375), plate 15, fig. 494. Valves linear-lanceolate, with cuneate apices, median portion sometimes somewhat attenuate; transverse striae robust, 7 to 1 1 in 1 c.d.m. Length, 2 to 5 c.d.m. Breadth, 1 to 15 c.d.m. Brackish water. — Antwerp ; sometimes fresh water. — Brussels Botanical Gardens (Delogne); England; Ireland (O'Meara). var. calida. (N. calida Grim. Arct. D., p. 75 ; H.V.H. Atl., pi. 59, f. 4 and 5*) plate 15, fig. 495. Valve linear, constricted at the median portion, with apices somewhac rostrate; sulcus scarcely visible ; striae 17 to 19 in 1 c.d.m. Keel with points rather distinct. Length, 3-5 to 4-5 c.d.m. Fresh water (warm). — Brussels Botanical Gardens (Delogne). var. littoralis Grun. (N. littoralis Grun. ; H.V.H. Atl., pi. 59, f. 1-3* ; in Type No. 190), plate 15, fig. 496. Distinguished from the type-form by the well marked carinal dots, and by the compact striation of the valve. Fresh or brackish water. — Antwerp (Park lake). N. debilis (Arnott) Grun. ! (Arct. Diat.,P. 68; H.V.H. Atl., pi. 57, f. 19-21* ; in Type No. 146), plate 15, fig. 497. Valve lanceolate elliptic, with subrostrate apices ; striae very feeble, 1 2 to 14 in 1 c.d.m., interrupted in the middle of the valve. Length, 2 to 2*5 c.d.m. Breadth, about 1 c.d.m. Fresh water. — Frahan, Groenendael (Del), Maryhill Bridge, near Glasgow, Scotland (W. Am., No. 847 !). N. angustata (W. Sm.) Grun. (Arct. Diat., p. 7°; H.V.H. Atl., pi. 57, f. 22-24*; in Type No. 475) plate 15, fig. 498. BB 386 NITZSCHIA. Valve narrowly linear, with apices produced ; stria; robust, not interrupted, 13 in 1 c.d.m. Length, about 8 to 9 c.d.m. ; breadth, about 1 c.d.tn. Fresh and brackish water.— Antwerp. England (W. Sm. ). Scotland (Baxter Coll., Nos. 2733, 2837). Ireland (O'Meara). var, curta. (H.V.H. All., pi. 57, f. 25*; Type No. 376), plate 15, fig. 499. Valves much shorter, with apices somewhat rostrate. Fresh water.— Brussels (Delogne). England, France, Denmark, Sweden. Group 2. — Panduriformes. Valves broad, constricted at the median portion, showing a more or less pronounced sulcus. Keel approximate to one of the margins, with dots either very distinct or apparently absent. Stria; decussate. ANALYSIS OF SPECIES. f Sulcus very deep, carinal dots very distinct N. panduriformis. (^Sulcus indistinct, carinal dots not distinct . N. constricta. N. panduriformis Grun. ! (Diat. Clyde, pi. 6, f. 102 ; h.v.h. Atl., pi. 58, f. 1-4*; Type No. 377 forma), plate 15, fig. 500. Valve broadly elliptic, with apices subrostrate, cuneate ; sulcus strongly marked, and bordered with a hyaline line or irregularly punctate ; striae decussate, 14 to 19 in 1 c.d.m. Carinal dots well marked, about 6 in 1 c.d.m. Length, 8 to 12 c.d.m. Breadth, about 2 c.d.m. at the median constriction Marine. — Not yet found in Belgium. England (Greg., Stolt. ), Bahnsie (Lagers). N. constricta (Greg.) Grun. ! Arct. Diat., p. 71; h.v.h. Atl., pi, 58, f. 8*), plate 15, fig. 501. Differs from the preceding species by its coarser puncta, its more pronounced sulcus, and by the dots of th2 keel which are not distinct Length, about 5 c.d.m. Marine. — Scheldt. England. forma parva. (H.V.H. Atl., pi. 58, f. 8*), plate 15, fig. 502. Very small, only attaining a length of about 1*5 c.d.m. Striae, 16 or 17 in 1 c.d.m. NITZSCHIA. 387 Group. 3. — Apiculat.k. Valves longly linear or somewhat attenuate at the median portion, showing a sulcus on which the stria; are absent, or are less marked than on the remainder of the valve. Keel very approximate to one of the margins. ANALYSIS OF SPECIES. f Keel with very j Valve very large ; sulcus broad N- Plana distinct dots. ) ,, , , ,. , „ „ . \ V alve narrowly linear ; sulcus narrow . . . N. Hungarica. I Keel with indistinct (Sulcus very broad ; valve of medium size, robust . N. acuminata. i. (.Sulcus veiy narrow ; valve small, very narrow . N. apiculata. N. plana, W. Sm. (S.B.D., I, p. 42, pi. 15, f. 114; H.v.H. Atl., pl. 58, f. 10, 11*; Type No. 37S), plate 15, fig. 503. Valve longly linear, attenuate at the median portion, with cuneate apices, broad well-marked sulcus, generally attenuate at the median portion, somewhat more distant from the carina! margin than the other margin ; striae fine, about 18 in 1 c.d.m., constantly replaced in the sulcus by very irregular puncta. Carinal dots very distinct, square or elongated, 3^5 to 6 in 1 c.d.m. Length, attaining to 17 c.d.m. Brackish water. — Not yet found in Belgium. England (W, Sm. ! Comber, Norman, Stolt. ). Ireland (O'Meara). N. Hungarica Grun. ! (Arct. Diat., p. 73 ; h.v.h. Atl., pi. 58, f. 19-22*; Type No. 3S0), plate 15, fig. 504. Valve narrowly linear ; generally feebly constricted in the middle ; apices cuneate, rostrate; sulcus narrow7, very distinct; striae fine, 16 to 18 in 1 c.d.m., very delicate in the sulcus; carinal dots very distinct, 9 or 10 in 1 c.d.m. Length, 5 to 1 1 c.d.m. Brackish, sometimes fresh water. — Antwerp, Schaerbeeck (Delogne). Ireland (O'Meara). England (H.V.H. Types, Nos. 7, 174, 186, 234, 389, 431,471). N. apiculata (Greg.), Grun. ! (Arct. Diat., p. 73; h.v.h. Atl, pl. 58, f. 26 and 27*; in Types Nos. 7, 12, 44, etc.), plate 15, fig. 505. Differs from the preceding species by its valves being generally smaller and narrower, and by the carinal dots being absent or indistinct. Striae about 16 or 17 in 1 c.d.m. Length, 2-5 to 5 c.d.m. Breadth of valves, less than 1 c.d.m. Brackish water. — Antwerp. England. Scotland. Finmark. Ireland (O'Meara). 3^8 NITZSCHIA. N. acuminata (W. Sm.) Grim. ! (Arct. Diat., p. 73; h.v.h. Atl., pi. 58, f. 16 and 17*; Type No. 379), plate 15, fig. 506. Valve broadly linear, sometimes constricted in the median portion, with a very broad and conspicuous sulcus. Strife very strong, about 12-5 to 13 in 1 c.d.m., very feeble or absent in the sulcus. Keel without dots. Length, 7 to 8-5 c.d.m. Brackish water.— Not yet found in Belgium. England (W. Sm.). Ireland (O'Meara, W.Sm.). Group 5. — ClRCUMSUT/E. Valves with sulcus more or less narrow, sometimes invisible, keel very eccentric, with conspicuous dots. Valves finely striate and showing in addition some irregular puncta. These two kinds of puncta belong to different layers of the valve. ANALYSIS OF SPECIES. Valve elliptic, very large ; string fine, undulated ; carinal dots very coarse, quadrangular . . , . N. circumsuta. N. circumsuta (Bailey) Grun. ! {Surfrella circumsuta Bailey; H.V.H. Atl., pi. 59, f. 8* ; Type No. 381), plate 15, fig. 507. Valve elliptic, very large, with sub-acute apices ; striae very fine, undulated, about 26 in 1 c.d.m. Carinal dots very coarse, quadrangular, 3 to 5 in 1 c.d.m. ; the median somewhat distant and showing between them a vestige of a nodule. Length, up to 21 c.d.m. ; breadth, up to 6*5 c.d.m. Brackish water. — Very rare: Antwerp (P. Gaut.) Maritime Scheldt. (H.V.H. ). Flessingue (Holland) (H.V.H., Deby.). England (W. Sm.). Group 6. — Dubi/E. Valves analogous to those of Tryblionella but without a sulcus. Keel eccentric. Girdle face attenuate at the median portion. ANALYSIS OF SPECIES. ' Carinal dots elongated on the valve ; valve rather broad . . N. dubia. ,. . , , , r Striae fine, valves small, distinctly rostrate . N. commutata. ] Carinal dots round '. I valve narrow. (striae very fine, valve of medium size, sub-rostrate . N. thermalis. NITZSCHIA. 389 N. dubia W. Sm. ! (S.B.D.,i., p. 41, pi. 13, f. 112 ; H.v.H. Atl., pi. 59, f. 9-12*; Type No. 3S2), plate 15, fig. 508. Valves linear, somewhat constricted at the median portion, with sub- rostrate apices; stria? fine, 21 to 24 in 1 c.d.m. ; keel with 9 or 10 dots in 1 c.d.m., slightly prolonged on the valve. Length, about 9 to 16 c.d.m. Fresh water. — Antwerp. Schaerbeeck (Delogne). England (W. Sm. !). N. thermalis(Kutz.)Grun. ! (Arct. Diat., p. 78; H.v.H. Atl., pi. 59, f. 20 ; in Type No. 74 var. litloralis), plate 15, fig. 509. Differs from the preceding species by its narrower valves and round carinal dots, the two median of which are somewhat distant. Striae fine, about 28 in 1 c.d.m. ; carinal dots about 7 or 8 in 1 c.d.m. Length, about 8 to 10 c.d.m ; breadth, about 1 c.d.m. Fresh water.— Aid. Lieg. (De Wild.). Ireland (O'Meara). var. intermedia Grun. (H.V.H. Atl., pi. 59, f. 15-19*), plate 15, fig. 510. Valves small (5 to 6 c.d.m.) and narrow (somewhat more than "5 c.d.m., with small carinal dots (9 in 1 c.d.m.), the two median of which are slightly distant ; stria? very fine, about 32 in 1 c.d.m. Freshwater. — Ard. Lieg (DeWild.). var. littoralis Grun. (H.V.H. Atl., pi. 59. f. 21). England. N. commutata Grun. (Arct. Diat., p. 79; H.V.H. Atl., pi. 59, f. 13 and 14*), plate 15, fig. 511. Valve longly linear, constricted at the median portion, with apices distinctly rostrate, rostrum obtuse. Carinal dots round, the two median distant. Stria? fine, 21 to 24 in x c.d.m. Carinal dots 9 or 10 in 1 c.d.m. Length, 5 to 7 c.d.m. Breadth, 1-25 to 175 c.d.m. Brackish water. — Not yet found in Belgium. England (W. Sm.) Group 7. — BlLOBATVE. Differs from the preceding group by the more central position of the keel. N. bilobata W. Sm. (S.B.D., i., p. 42, pi. 15, f. n3; h.v.h. Atl., pi. 60, f. t*), plate 15, fig. 512. Valve linear, lanceolate, constricted at the median portion, with apices abruptly attenuate, rostrate, acute. Keel almost central, with carinal dots 39° NITZSCHIA. transversely elongated. Stride fine, about 17-5 to 19 in 1 c.d.m. Carinal dots about 6-5 to 7 in 1 c.d.m. Girdle face very broad, constricted at the median portion, with connecting zone finely plicate. Length, S to 15 c.d.m. Marine. — Not yet found in Belgium, but found in England (W. Sm., Comber, Norman, Stolt. ). Ireland (O'Meara), and throughout most of Europe. var. minor Grun. (H.V.H. All., pi. 60, f. 2 and 3*), plate 15, fig- 5*3- Small (5 to 7 c.d.m. in length) with very fine striae (23 to 27 in 1 c.d.m. Marine. Group 9.— Grunowia. Keel very eccentric, with dots elongated into costae, which generally occupy a moiety of the valve. ANALYSIS OF SPECIES. J' Valves narrowly lanceolate, with margins not sinuouj ; costos diminishing very gently in breadth . . . . . N. Denticula. Valve with margins sinuous or strongly inflated at the median portion ; costoe stopping abruptly in the middle of the valve . . N. sinuata. N. Denticula Grun. ! (Arct. Diat, p. 82 ; H.V.H. Atl., pi. 60, f. 10*; Type No. 384), plate 15, fig. 514. Valves narrowly lanceolate, with apices acute or subacute, not rostrate, furnished with costal which most frequently traverse the entire valve, while diminishing very gently in breadth ; stria? fine, 15 to 18 in 1 c.d.m., distinctly punctate; costs} 6 to 8 in 1 c.d.m. Length, 1*5 to 4^5 c.d.m. Fresh water. — Throughout Europe. var. Delognei Grun. ! (H.V.H. Atl., pi. 60, f. 9*), plate 15, fig- 5i5- Costse not reaching, at most, farther than to a moiety of the valve ; striae very delicate, 24 or 25 in 1 c.d.m. Length, 1 to 2 c.d.m. Fresh water. — Brussels Botanical Gardens (Delogne). N. sinuata (W. Sm.) Grun. ! (Arct. Diat., p. 82 ; H.V.H. Atl., pi. 60, f. n* ; Type No. 385), plate 15, fig. 516. Valve lanceolate, with margins triundulate, median portion inflated, apices rostrate-capitate ; costae 5 or 6 in 1 c.d.m., only occupying a moiety of the NITZSCHIA. 391 valve, and equally robust throughout their length ; striae about 18 in 1 c.d.m., distinctly punctate. Length, about 4 c.d.m. Fresh water. — Frahan (Delogne); England, France, Germany, etc; Scotland (Greville, Hennedy). var. Tabellaria Grun. ! (Arct. Diat, p. 82 ; H.V.H. Atl., pi. 60, f. 12 and 13*; Type No. 386), plate 15, fig. 517. Valve very inflated in the median portion, with apices longly diminuate rostrate; costoe 6'5 to 7*5 in 1 c.d.m.; striae 21 or 22 in 1 c.d.m., delicately punctate. Fresh water. — Brussels (Delogne). Group 10. — SCALARES. Distinguished from the preceding groups by the keel being more acute and less eccentric. N. scalaris W. Sm. (S.b.d., i., p. 39, pi. i4, f. 115 ; h.v.h. Atl., pi. 60, f. 14-15* ; Type No. 387), plate 32, fig. 874. Valve broadly linear, with conical apices, costs of unequal length, 3 to 5 in 1 c.d.m.; transverse striae narrowly punctate, 9 to 1 1 in 1 c.d.m. Frustule in transverse section quadrate or in form of an oblong square. Length, up to 48 c.d.m. Breadth of valves, 2 to 2*5 c.d.m. Brackish water. — England (W. Sm., Norman, Stolt. ), France (De Breb.), Denmark (Heiberg). Group 11. — Insignes. Similar to the forms of the preceding group, but with a keel still more eccentric and frustules sometimes somewhat sigmoid. N. insignis Greg. (T.M.S., 1857, v., p. 80, pi. 1, f. 46; H.V.H. Atl., pi. 61, figs, various*), plate 32, fig. 875. Valves linear, lanceolate, with apices subconical, produced, keel almost central, broad, straight or gently curved. Costae rather long, 4 or 5 in 1 c.d.m. Striae, 10 or 1 1 in 1 c.d.m., strongly punctate. Frustules straight, linear. Length, up to 40 c.d.m. Marine. — Coasts of England (Norman), and Scotland (Gregory). var. Smithii. (A7, spectabilis W. Sm.; H.V.H. Atl., pi. 61, f. 4*), plate 32, fig. 876. Distinguished from the type-form by being slightly sigmoid; costae short, 2 or 3 in 1 c.d.m. Striae 13 or 14 in 1 c.d.m. Brackish water. — England (Norman), France (De Breb). 392 NITZSCHIA. Group 12. — Bacillaria. Keel central or almost central, with dots not elongated. Frustules straight. Striation conspicuous. ANALYSIS OF SPECIES. Keel almost central, frustules united in a stratum. . . N. paradoxa N. paradoxa (Gmel.) Grun. ! {Bacillaria paradoxa Gmel.\ H.V.H. Atl., pi. 61, f. 6* ; Type No. 388), plate 15, fig. 518. Valves narrowly lanceolate, with apices feebly rostrate. Keel almost central, with 6 to 8 coarse round dots in 1 c.d.m. Strice 20*5 to 22^5 in 1 c.d.m. Frustules united in a stratum, displaced by a sliding movement of one frustule over another. Length, about 6 c.d.m. Brackish water. — Blankenberghe, Ostend, Antwerp. England, Ireland, and almost everywhere. Sometimes found in water containing only a trace of salt. Canal at Louvain (P. Gaut. ). var. major. (H.V.H. Atl., pi. 61, f. 7*), plate 16, fig. 519. Group 13.— VivaClS. Valves semi-lanceolate, with margins showing elongated carinal dots. Valves similar to those of Hantzschia, but not showing (like those of the species of that genus) a vestige of a central nodule. ANALYSIS OF SPECIES. f Valve semi-lanceolate, strongly arcuate, very small, with rostrate apices ; striae very delicate . . N. Petitiana. I Valve semi-lanceolate elliptic, large, with rostrate apices ; stria; rather [ robust . . . . . N. vivax. N. vivax W. Sm. ! (S.B.D., i., p. 4t, pi. 31, f. 267; H.V.H. Atl., pi. 62, f. 1-2* ; in Type No. 389), plate 33, fig. 877. Valve semi-lanceolate, elliptic, with ventral margin straight, dorsal margin arcuate, apices produced rostrate. Carinal dots somewhat elongated, 6 in 1 c.d.m. ; striae 12 in i c.d.m., finely punctate. Frustules linear. Length, 10 to 16 c.d.m. Breadth of valves, 1*3 c.d.m. Marine. — England (W. Sm., Comber, Norman), Ireland (O'Meara). NITZSCHIA. 393 N. Petitiana Grim. (H.V.H. Atl, pi. 62, f. 6*), plate 16, fig. 520 Valve small, with ventral margin straight, dorsal margin very gently and regularly attenuate up to the apices, which are rostrate. Carinal dots 8 or 9 in 1 c.d.m., scarcely prolonged. Striae delicate, about 27 to 30 in 1 c.d.m. Brackish water. — Not yet found in Belgium. Group 14. — SPATHULATA. Analogous to Bacillaria from which it is differentiated by the very delicate striation of the valves and by two auxiliary lines parallel to the keel. ANALYSIS OF SPECIES. I Girdle face showing the apices of the keel enlarged and elevated . N. spathulata. f Valve with apices longly rostrate . . . N. cursoria. -j t- . I Valves f Carinal dots, 1-5 to 3 in 1 c.d.m. ; apices some- I , ! , -: with what produced . N. distans. elevated • ' apices -; not j Carinal dots. 3 '5 to 5 in 1 c.d.m. ; apices not t, costrate. l. produced . . . N. angularis. N. angularis W. Sm. ! (S.B.D., i., p. 40, pi. 13, f. 117 ; H.V.H. Atl., pi. 62, f. n-14*), plate 16, fig. 521. Valve narrowly lanceolate, very gently attenuate up to the subobtuse apices. Valve with keel central, 3 "5 to 5 marginal dots in 1 c.d.m. ; auxiliary lines clearly visible; transverse striae delicate, 31 or more in 1 c.d.m., formed of puncta which equally produce longitudinal and oblique striae. Girdle face broadly linear, somewhat inflated at the median portion, with connecting zone plicate. Length, 6 to 20 c.d.m. ; breadth of valves, about 1 to 1*5 c.d.m. Marine. — Washings of Mussels (Deby). England (W. Sm. ! Comber, Norman), Ireland (O'Meara), Scotland (Baxter Coll., No. 2765). var. affinis Grun. (H.V.H. Atl., pi. 62, f. 16*), plate 16, fig. 522. Differs from the type-form by its smaller size (3 to 9 c.d.m. in length) and its more approximate carinal dots (6 to 9 in c.d.m.), and its still finer striae. N. spathulata Breb. (in w. Sm., S.B.D., i., p. 4o, pi. 31, f. 268; H.V.H. Atl., pi. 62, f. 7 and 8*; Type No. 390), plate 16, fig. 523. 394 NITZSCHIA. Differs from the preceding species by the apices of the keel, which are much enlarged and elevated. Carinal dots 4 or 5 in 1 c.d.m. Strise excessively delicate. Length, about 10 c.d.m. Marine— Blankenberghe, Antwerp (Scheldt H.V.H.), France (Br6b.), Denmark (Heib. !), England (Harrison, Norman), Ireland (O'Meara). var. hyalina (H.V.H. Atl., pi. 62, f. 9*), plate 16, fig. 524. Very small (about 4 c.d.m.), about 7 or 8 carinal dots in 1 c.d.m. Same habitat. N. distans Greg. (Diat. of Clyde, p. 58, pi. 6, f. 103; H.V.H. Atl., pi. 62, f. 10*), plate 33, fig. 878. Valve narrowly lanceolate, with apices somewhat produced, sub-rostrate ; keel central with dots unequally distant, 1*5 to 3 in 1 c.d.m. Stria; excessively delicate and approximate. Girdle face linear, with sub-truncate apices, showing the keel somewhat alate. Length, up to 15 c.d.m. Marine. — England (Stolt.), Glenshira sand, Scotland (Gregory), Bahnsie (Lagerstedt). N. cursoria (Donk.) Grun. (Arct. Diat, p. 89; H.V.H. Atl., pi. 62, f. 19* ; Bacittaria cursoria Do/ik.,) plate 33, fig. 879. Valve very narrowly lanceolate, with apices longly rostrate, keel central, narrow, with about 10 dots in 1 c.d.m., accompanied by two accessory lines, distant about -4 c.d.m. Striation very fine. Frustule linear, with truncate apices. Length, 7 to 8 c.d.m. Breadth of valve, 7 c.d.m. Marine. — England (Donkin, Norman), France (Br£b.). Group 15. — DlSSIPAT/E. Differs from the two preceding groups by the keel being less central and the absence of auxiliary lines. Valves very small and very delicately striated. ANALYSIS OF SPECIES. Keel not quite central. Valves very small and delicately striated . N. dissipata. N. dissipata (Kiitz.) Grun. ! (Arct. Diat, p. 90; N. minutissima W. Sm. ? ■ H.V.H. Atl., pi. 63, f. 1*; Type No. 391), plate 16, fig- 525- NIT2SCHIA. 395 Valve lanceolate, with apices very slightly rostrate. Keel slightly eccentric, with 6 to 8 dots in i c.d.m. Striae excessively faint (about 14 in 1 c.d.m. according to Mr. Kitton). Length, 2 to 3*5 c.d.m. Fresh and brackish water. — Antwerp (H.V.H.) Schaerbeeck (Delogne). Aid. Lieg. (De Wild.). Here and there in Europe. var. media. (H.V.H. Atl., pi. 63, f. 2 and 3* ; Type No. 190), plate 16, fig. 526. Valves larger, with apices sometimes subrostrate, capitate, keel some- what more eccentric, with 6 or 7 dots in 1 c.d.m. Length, 4-5 to 7 c.d.m. var, acuta. (H.V.H. Atl., pi. 63, f. 4*), plate 16, fig. 527. Valves longer, attaining to io-5 c.d.m., with keel quite central, 6 or 7 dots in 1 c.d.m. Group 16. — SlGMOIDEzE. Valves without sulci, keel quite central, without auxiliary lines, carinal dots not elongated. Girdle face sigmoid, with apices not produced. ANALYSIS OF SPECIES. f Strire very robust; carinal dots round. Brackish water species . N. Brebissonii. Strix' fine ; carinal f Striae fine ; size very considerable ; carinal dots 4 -J dots somewhat to 7 in 1 c.d.m. . N. sigmoidea. elongated. -J Fresh water Striae very fine ; size medium ; 7 to 9 dots in 1 species. (. c.d.m. . . . . N. vermicularis. N. sigmoidea (Ehr.) W. Sm. (s.b.d., i., p. 38, pi. 13, f. 104 ; H.V.H. Atl., pi. 63, f. 5-7* ; Type No. 392), plate 16, fig. 528. Valves linear, with cuneate apices. Keel central, with 5 to 7 dots in 1 c.d.m. Strice fine, 23*5 to 26 in 1 c.d.m. Girdle face narrow, sigmoid, with truncate apices, connecting zone finely striated. Length, attaining 48 c.d.m. Fresh water. — Rather common everywhere. N. vermicularis (Kutz.) Grun. ! (Arct. Diat., p. 91; H.V.H. Atl., pi. 64, f. t and 2* ; in Type No. 96), plate 16, fig. 529. Differs from the preceding species by its smaller and narrower size, its closer carinal dots, 6 to 9 in 1 c.d.m., and shorter at the margin of the valve, as well as by its finer striae, 32 to 34 in 1 c.d.m. Length, 9 to 22 c.d.m. ; breadth of valve, about '5 c.d.m. ; breadth of girdle face, "5 to i*o c.d.m. Freshwater. — Belgium? England (H.V.H. Type No. 96). Scotland (W. Am.), (var. lampro campa. , Aid. Lieg. (De Wild. ). 396 NITZSCH1A. N. Brebissonii W. Sm. ! (S.B.D., i., p. 38, pi. 31, f. 226 ; H.v.H. Atl., pi. 64, f. 4 and 5* ; Type No. 393), plate 16, fig. 530. Valves straight, or curved, or arcuate, or sigmoid ; about 5 carinal dots in 1 c.d.m., apices rather abruptly attenuate, acute; striae very robust, 9 to 1 1 in 1 c.d.m. Length, 22 to 24 c.d.m. Breadth of valve, 1*3 to 1*5 c.d.m. Brackish water. — Heyst (Deby). Antwerp. England (W. Sm., Comber, Norman), Ireland (O'Meara). France, etc. Group 17. — SlGMATA. Valves still less sigmoid, keel somewhat more eccentric than in the preceding group. Girdle face sigmoid, with apices produced. ! ANALYSIS OF SPECIES. Keel with coarse, very projecting dots . . . N. fasciculata. Keel with rather delicate dots . . . . N. Sigma. N. Sigma, W. Sm. ! (S.B.D., i, p. 39, pi. 108; H.v.H. Atl, pi. 65, f. 7 and 8* ; Type No. 394), plate 16, fig. 531. Valves linear, somewhat sigmoid, with apices very slightly produced. Keel eccentric, with 7 to 9 dots in 1 c.d.m. Striae fine, 22 to 24 in 1 c.d.m. Girdle face sigmoid, with tapering apices. Length, attaining 25 c.d.m. Breadth, a little more than ro c.d.m. Brackish water. — Antwerp, Blankenberghe. England, (W. Sm. ! Comber, Norman, Stolt) Ireland (O'Meara). France, Bahnsie. Finmark. var. intercedens Grun. (H.V.H. Atl, pi. 66, f. 1*), plate 16, fig. 532. Large and generally very much curved, with 6 to 7 carinal dots, and 27 or 28 striae in 1 c.d.m, the valve being about 1 c.d.m. broad, and up to 30 c.d.m. long. Brackish water. — Antwerp (Scheldt, Belleroche). var. rigida (Kiitz.) Grun. (Amp/iipleura rigida K'utz. ; A. sigmoidea, W. Sm. ; H.V.H. Atl, pi. 66, f. 2* ; in Type No. 395), plate 16, fig. 533- Valve narrowly lanceolate, sigmoid, with 7 to 9 carinal dots, and 30 or 31 striae in 1 c.d.m. Valves attaining a length of 20 c.d.m, and a breadth of 8/x Freshwater. — Brussels, Antwerp. England (W. Sm., Comber, Norman). Scotland. Ireland (O'Meara). var. rigidula Grun. (H.V.H. Atl, pi. 66, f. 8*; Type No. 396), plate 16, fig. 534. NITZSCHIA. 397 Differs from the preceding variety by its smaller size and breadth, 8 to 10 carinal dots, and 30 or 31 striae in 1 c.d.m. Length, about 6 to 7 c.d.m. Breadth, less than 0*5 c.d.m, Fresh water. — Rouge-Cloitre (Delogne). var. Sigmatella Grun. (H.V.H. Atl., pi. 66, f. 6 and 7* ; Type No. 397), plate 16, fig. 535. Valves very narrowly lanceolate, sigmoid, with S to 1 1 carinal dots in 1 c.d.m., and 25 or 26 striae in 1 c.d.m. Valves attaining 32 c.d.m., (sometimes, but rarely, even 45 c.d.m.), and about 5 c.d.m. in breadth. Brackish water. — Ostend. N. fasciculata Grun. (Honuzorfadia sigmoidea, IV. Sm. ; H.V.H. Atl., pi. 66, f. n-13*), plate 16, fig. 536. Valve more or less sigmoid, sometimes almost straight. Keel with coarse dots, somewhat elongated, 5 or 6 in 1 c.d.m. Striae fine, 28 or 29 in 1 c.d.m. Frustules often united in small fascicles. Length, 5 to 10 c.d.m. Marine or brackish. — Ostend (Grunow), Antwerp. England (W. Sm.). Group 18. — ObtuSjE. Analogous to the preceding groups, from which it is distinguished by the keel, which in the middle of its length shows an inflection at the internal portion, and at the same part two somewhat distant dots between which the rudiment of a nodule appears. ANALYSIS OF SPECIES. Keel showing in the middle of its length an inflexion, at which the two median dots are somewhat distant, and between them the rudiment of a nodule is shewn . . . . . . . N. obtusa N. obtusa W. Sm. ! (s.b.d., i, p. 39, pi 13, f. 109; h.v.h. Atl., pi. 67, f. 1* ; Type No. 398), plate 16, fig. 537. Valve linear, with apices rounded or abruptly attenuate unilaterally. Keel with 5 or 6 coarse dots. Median inflexion very visible. Striae fine, 26 or 27 in 1 c.d.m. Length, 12 to 25 c.d.m. Breadth of valves somewhat less than -8 to "9 c.d.m. Brackish water— Blankenberghe (H.V.H.), Aid. Liege (De Wild.), England (W. Sm. ! Stolt.), Denmark, Holland, &c. var. scalpelliformis. (Arct. Diat., p. 92 ; H.V.H. Atl., pi. 67, f. 2*), plate 16, fig. 538. 398 NITZSCHIA. Shorter, narrower, and with apices more sigmoid and more abruptly attenuate unilaterally; 7 or 8 carinal dots and 26 or 27 strise in 1 c.d.m. Length, 6 to 8 c.d.m. Breadth of valves, about -75 c.d.m. Brackish water. — Ard. Lieg. (De Wild.). var. nana Grun. (II.V.H. Atl, pi. 67, f. 3* ; Type No. 399), piate 16, fig. 539. Quite small, sigmoid, with 10 or 11 carinal dots and about 35 strise in 1 c.d.m. Length, about 4 c.d.m. Distinguished from analagous forms of N. Sigma by the conspicuous central pseudo-nodule (Grunow). Brackish water. — Not yet found in Belgium. var. brevissima Grun. (H.V.H. Atl., pi. 67, f. 4* ; Type No. 400), plate 16, fig. 540. Valves linear, rather broad, somewhat constricted at the median portion, with rostrate, gendy sigmoid apices. Carinal dots coarse, about 8 in 1 c.d.m. ; striae, 30 to 36 in 1 c.d.m. Brackish water.— Piles in the Scheldt at Antwerp (H.V.H. ), Ard. Lieg. (De Wild.). Group 19.— Spj-ctabiles. Valves large, slightly arcuate, with eccentric keel. Carinal dots somewhat prolonged on the valve. ANALYSIS OF SPECIES. Valves large, slightly arcuate, with eccentric keel, carinal dots somewhat prolonged on the valve . . . . . . N. spectabilis. N. Spectabilis (Ehr.) Ralfs. {Synedra spectabilis Ehr. Amer. and Mikr., numerous figures; H.V.H. Atl., pi. 67, f. 8 and 9*; Type No. 401), plate 16, fig. 541. Valves linear, more or less arcuate, with apices attenuate, often rostrate- capitate ; keel very eccentric, with 4 to 6 dots in 1 c.d.m., often prolonged on the valve into a very short costa ; striae, ro to 12 in 1 c.d.m., distinctly punctate ; length, attaining 45 c.d.m. Brackish water. — Scheldt at Antwerp. Probably England. Group 20. — LlNEARES. Valves without sulci. Keel somewhat eccentric, with round or somewhat angular carinal dots, just a little elongated transversely. Girdle face straight, sometimes slightly attenuate at the median portion. NITZSCHIA. 399 ANALYSIS OF SPECIES. '8 to 12 faint carinal dots in i c.d.ra. ; valve showing a slight inflexion at the median portion . . . . . . N. linearis. .5 to 7'S very robust carinal dots in i c.d.in. ; valv2 without median inflexion N. vitrea. N. linearis (Ag.) W. Sm. ! (s.b.d., i., p. 39, pi. 13, f. no, and Supp., pi, 31, f. no ; H.V.H. Atl, pi. 67, f. i3*-i5 ; Type No. 404), plate 16, fig. 542. Valves longly linear, almost in the form of a boat, with apices rounded at the external, and attenuate at the internal portion. Keel, 8 to 10 dots in 1 c.d.m., the two median more distant than the others, the space between generally corresponding with a small inflexion of the valve. Stride, 29 or 30 in 1 c.d.m. ; finely punctate. Length, 7 to 18 c.d.m. Breadth of valve, about -5 c.d.m. Fresh water. — Rather common throughout Europe. var. tenuis Grun. (H.V.H. Atl., pi. 67, f. 16; Type No. 406), plate 16, fig. 543. Valve narrow (-4 to 7 c.d.m.). Keel, n or 12 dots in 1 c.d.m. Striae more than 30 in 1 c.d.m., generally interrupted at the median portion of the valve. Girdle face "4 to '9 cd.m. Length, 7 to 15 c.d.m. Fresh water. — Common. N. vitrea, Norman ! (T.M.S., 1861, i, n.s., p. 7, pi. 2, f. 4 ; H.V.H. Atl., pi. 67, f. 10*), plate 16, fig. 544. Differs from the preceding species by the carinal dots (5 or 6 in 1 c.d.m.) being often coarser and quadrangular, rounded, and by the girdle face being very broad, sometimes constricted and by the connective zone having numerous plicae. Striae, 20 to 22 in 1 c.d.m. Length, 6 to 13 c.d.m. Breadth of valves, "5 c.d.m. ; breadth of girdle face, up to 2^5 c.d.m. Brackish water. — Scheldt at Antwerp. Ard. Lieg. (Dr. Wild.). Hull, England (Norman), Scotland (H.V.H. Type No. 382). forma major. (H.V.H. Atl., pi. 67, f. 11*; Type No. 402), plate 16, fig. 545. Valves up to 12*5 c.d.m. in length and 1*25 c.d.m. in breadth, with 17 striae in 1 c.d.m. var. salinarum Grun. (Arct. Diat., p. 94; H.V.H. Atl., pi. 67, f. 12*; in Type No. 431), plate 16. fig. 546. Smaller than the type-form (3*5 to 8-5 c.d.m. in length), valves broad (:$ to -9 c.d.m.), and striae narrower (28 to 30 in 1 c.d.m.). Brackish water. — Ostend (Grunow). 400 NITZSCHIA. var. recta (A7, recta Hantzsck; H.V.H. Atl., pi. 67, f. 17 and 18*), plate 16, fig. 547. Keel somewhat eccentric, with 6*5 to 7*5 dots in 1 c.d.m., the median more approximate than the others. More than 30 striae in 1 c.d.m. Frustules narrower than the preceding variety, about "6 to 1*2 c.d.m. in breadth). Fresh (?) and brackish water. — Ard. Lieg. (De Wild.) ; England (H.V.H. Type No. 96). Group 21. — LanceolaT/E. Valves lanceolate, linear lanceolate, or more rarely oval. Keel very eccentric, with dots not elongated. ANALYSIS OF SPECIES. f Connecting zone very broad and strongly plicate 1 I Median carinal dots somewhat more distant than the others I f Valves with apices rostrate-capitate o u u a G o c c o U Carinal dots all equidistant I Valves with apices not capitate. . N. lanceolata. N. subtilis. - N. microcephala. f Strice conspicuous (16 to 17 in 1 c.d.m.) N. amphibia. Strife indistinct, more than 20 in 1 c.d.m. I Valves linear, abruptly produced subrostrate ; carinal dots well marked ; strife very delicate (about 30 in 1 cd.m.) . . N Valves lanceolate, con- siderably rostrate ; car- inal dots faint ; strife very delicate (30 to 36 in 1 c.d.m. ) . , N. Valves narrowly lanceo- late or linear, more or less rostrate ; carinal dots faint ; strife more visible (20 to 22 in 1 c.d.m.) communis. Palea. N. Frustulum. Carinal dots not visible Strife invisible, 13 conspicuous carinal t dots in 1 c.d.m. . . . N. N. ovalis. Delognei. N. lanceolata, W. Sm. (S.B.D., i., pi. x4, f. n8; h.v.h., pi. 68, f. 1 and 2*; Type No. 407), plate 17, fig. 548. Valve narrowly lanceolate, with acute apices. Keel very eccentric, about 5 to 7 dots in 1 c.d.m., all equidistant. Striae fine, about 30 in 1 c.d.m. Girdle face linear, strongly inflated at the median portion, with obtuse apices and strongly plicate connecting zone. Length, up to 20 c.d.m. Breadth of valve, 175 c.d.m. Brackish water, — England (W. Sm., Norman, Stolt.), Ireland (O'Meara). NITZSCHIA. 401 forma minor. (H.V.H. Atl., pi. 68, f. 3*; in Type No. 397), plate 17, fig. 549. Only attaining 5-5 to 6 c.d.m. forma minima. (H.V.H. Atl., pi. 68, f. 4*), plate 17, fig. 550. Still smaller, and scarcely 2 c.d.m. in length. var. incrustans. (H.V.H. Atl., pi. 68, f. 5 and 6*), plate 17, fig- 551- Valves more narrowly lanceolate, with 5 to 7 carinal dots in 1 c.d.m. Stria; very fine, more than 30 in 1 c.d.m. Girdle face scarcely or not inflated at the median portion. Length, about 2 to 5 c.d.m. Breadth of valves, -4 to -6 c.d.m. ; breadth of girdle face, up to nearly 2 c.d.m. On piles in harbours. Ostond (Grun. !). Ilfracombe, England (Baxter Coll. No. 2627.) N. subtilis Grun.! (Arct. Diat., p. 95; H.V.H. Atl, pi. 68, f. 7 and 8* ; in Types Nos. 165 and 190), plate 17, fig. 552. Valves narrowly lanceolate, very gently attenuate as far as the apices. Keel with 7 to 10 dots in 1 c.d.m., the two median generally somewhat more distant. Strioe fine, 30 to 32 in 1 c.d.m. Girdle face narrow, with apices very slightly attenuate. Length, up to 9-5 c.d.m. Breadth of valve, about -5 c.d.m. ; and of girdle face, about 6 c.d.m. Fresh water. — Rather common (?). var. paleacea Grun. (Arct. Diat., p. 95 ; H.V.H. Atl., pi. 68, f. 9 and 10*; in Type No. 10), plate 17, fig. 553. Smaller and narrower, valves attaining to 2^5 to 3*5 c.d.m. in length, and "3 to '4 c.d.m. in breadth. Keel with 12 to T4 dots in 1 c.d.m. Stria; very fine. Fresh and brackish water. — Common (?) N. Palea (Kutz.) W. Sm. (S.B.D.,ii.,p.s9;H.v.H.Ati.,pi. 69,f. 22^ and 2 2■•>: : ■*."•:•.'•••-••.•;•;•.■•'••* » -• ••• • # , •_ '. » »,lf,»Ti'1'f,l •'.i.*.'.*!f ".•;*'••' •"•■""-• .■•.•.••>»>»>>> 130 Fig. x&.—Trybhonella punctata. Fig. 129.— Pritchardia insignis var. Mcditerianca. Fig. 130 — Perrya pukhcrrima. 4o8 GOMPHONITZSCHIA. N. (H.) subcohcerens Grun. (Diat Kasp, p. 23 ; h.v.h. Atl., pi. 66, f. 14*), plate 35, fig. 915. Valves 3 c.d.m. in length, -4 in breadth; 9 or 10 carinal dots, and 33 or 34 transverse stria; in 1 c.d.m. Frustules living solitary or united in dense fascicles (Grunovv). Marine.— Leith, Scotland (Frauenfeld). N, (H.) sigmoidea, W. Sm., is nothing else but AT. fasciculate. Grun., which we have previously described. Tryblionella, W. Sm. (figure 128) and Pritchardia Rab. (figure 129), are both true Nitzschia, as well as Perrya Kitton, 1877, (figure 130), which is distinguished by its carinal dots being prolonged into long interrupted lines, so as to appear to form long rows of coarse dots. All the Perrya are exotic. The most remarkable species of this group is the Perrya pulchcrrima {Grun. and Kitton), which will be found reproduced on the preceding page. GENUS 82. -GOMPHONITZSCHIA GRUN., 1868. Frustules similar to those of Nitzschia, but with cuneate valves and girdle face. The frustules are sessile or stipitate, and in that case they grow fiabilliform. Fig. 131. Gomphonitzschia Ungeri. The Gomphonitzschia are, therefore, gomphonemoid Nitzschia. The genus only includes two species, one G- Ungeri Grun. (fig. 131), inhabits Egypt, and the other, G. Clevei Grun., has been found in Batavia. CYLINDROTHECA. 409 Tribe XVlII.—Cylindrothecece. GENUS 83.— CYLINDROTHECA RABH, 1859. Frustules fusiform, furnished with 2 or 3 lines (carinae?), arranged spirally, and showing juxta- posed (carinal ?) dots. One species. C. gracilis (Breb.) Grun. ! {Ceratoneis Breb. ; Nitzschia Ticnia, IV. Sm. ; Cyhndrotheca Gerstenbergeri Rab. ; H.V.H. Atl., pi. 80, f. 2*; Type No. 417), plate 17, fig. 574. Frustule becoming abruptly fusiform ; spiral line with 20 to 22 elongated dots in 1 c.d.m. Length, about 7 to 8 c.d.m. Freshwater. — Brussels (Delogne). Antwerp (H.V.H. ), England (Ralfs, W. Sm., Comber, Stolt., Norman). Fig. 132. Cylindrotheca gracilis. 4io CRYPTO-RAPHIDIE/E. SUB-FAMILY III.— CRYPTO-RAPHIDIE^E. Frustules with valve face gen- erally circular, subcircular, or angular, more rarely elliptic, oval, or bacillar. frequently never much developed in girdle view and filamentous ; or with processes, teeth, spines, or awns ; or more or less hyaline ; or irregular ; or furnished with transverse costae in girdle view. r i with a central linear blank (hyaline) space or a true 1 raphe on the valves. All the crypto-raphidiese have a granular endochrome ; in cylindrical forms the granules are scattered on the internal surface of the valves ; in discoid or analogous forms the granules radiate round a central point. CRYPT0-RAPHID1E/E. 411 TABLE OF TRIBES. Frustules cylindrical or flattened. Valves alike, terminated by a calyptra (hood), pointed with a bristle ; or frustules with valves unlike or mostly smooth ; furnished with awns, horns (elongated processes), spines or seta;, which in fossil forms are sometimes imperfect or absent ; frustules often imperfectly silicious. Valves without radial or cellulose costae ; or again, frustules imperfectly silicious, united in distant series; connecting zone more or less turgid. Valves angular, with a long central spine . I Frustules cohering ; girdle face generally much developed and cylin- drical; firmly silicious. Valves rarely hyaline ; unlike or elliptic and without median line, sometimes apiculate or conical or with a peculiar central nodule (spine); or umbilicus, smooth, punctate or cellulate, and frequently with marginal or submarginal spines. Frustules cohering either by teeth or marginal spines, or by a central spine or a short central cushion ..... Girdle face much developed, valves of very different forms, some- times furnished with horns or simple spines or prominences at the apices ; always without ocelli or radiating septa . D > Z Chsetocerese. Melosirese. Biddulphiese. o 2 1 O c as > Valves round or elliptic, | Compartments alternately elevated and depressed Heliopeltese. divided into j radiating ] compart- | Compartments arranged on the same plane . Aster Olamprese merits. (. Valves not divided into radiating compart- ments. f Valves always round or very broadly elliptic, furnished with one or more ocelli or with very short obtuse horns, simulating ocelli . Eupodisceae. Valves generally round or elliptic, rarely elonga- ted, semi-lunar or cuneate ; with cellulate or punctate structure ; sometimes furnished with small, short and slender spines, always without ocelli ..... Coscinodiscus. 412 CH^TOCERE^;. Tribe XIX. — Ciletocere.e. Frustules consisting of numerous imbricate or juxtaposed hoops. Frustules not consisting of numerous hoops. Valves symmetri- cal. Valves asymmetri- cal. Valves bordered with extremely long spines. Without awns, sometimes a circlet of marginal dots ..... I | Furnished with numerous more or less developed awns ..... Valves elliptic, furnished with two awns k Valves round, with two long spine-like horns Valve showing an undulation terminating in a rudimentary mucro, placed laterally | Valve calyptriform, showing a more or less [ developed mucro, generally ending in a seta . Spines not arranged in a circle on the margin of the valve .... No very long marginal spines. Spines arranged in a circle. A long central spine. f Spines forming a flat corona (rays) round the valve 1 i_ Spines erect ■ f Valve angular, very slightly sili- cious ; spine setiform Valve rounded, with two biddul- phiform marginal elevations and with a central spine ter- minating in a forked claw ' Valv tic o ^H tu G > o '~ w J3 «-T C rt t/i J- 3 O w XSJ2 - rt O c~ *_. >- 0 o -, w c CD in CD 'S, > 72 a > . Valve with a cylindrical central eleva- tion, bordered with very robust spines Dactyliosolen. Lauderia. Attheya. Peragalloa. Guinardia. Rhizosolenia. Chsetoceros. Bacteriastrum. Corethron. Ditylum. Syndetoneis. Pyrgodiscus. Frustules compressed, with su- tural portion narrow ; horns often branching or bifurcate, sometimes mucronate. Valves sometimes short and obtuse, at other times furnished with short scattered spines Fiustules elongated, with mucro- nate horns. Generally one of the valves with only one horn or process and the other with two Valves dissimilar, furnished with rather short setiform spines . Valves similar, smooth or hyaline, fossil, without spines, often united by a constricted central part Valves furnished with small scattered spines Dicladia. Syringidium. Hercotheca. Goniothecium. Chsetoceros. I. RlIIZOSOLENlE.E. imbricate or juxtaposed hoops (annuli). Frustules consisting of numerous The Rhizosolenieae are the subject of an excellent monograph by Mr. H. Peragallo inserted in Le Diatomiste for 1892, to which we refer the reader for a complete examination of this sub-tribe. \ - : 'II . - m ~4- mm Fig. 133. — Rhizosolenia styliformis. GENUS 84.-RHIZOSO- LENIA (Ehr. Brightw.) Perag. era., 1892. Frustules subcylindricai, very elongated, silicious, con- sisting of numerous joints with an annulate or imbricate arrangement ; valves asym- metrical, generally termina- ting in a hood (calyptra) sur- mounted by a bristle (seta) or mucro. About 40 species in this genus have been described, but only some 30 deserve attention. Seven inhabit the North Sea. 414 RHIZOSOLENIA. Mr. Peragallo divides the Rhizosolenix into three groups, which we adopt here, viz. : — GROUP I. Annulate? . — Frustules annulate. R. robusta Norm, (in Pritch. Inf., p. 866, pi. 8, f. 42 ; Perag., pi. 2, f. 1, and pi. 3, f. 1-2*), plate 33, fig. 883. Frustule cylindrical, depressed ; section elliptic, axis curved, hood consist- ing of annuli with antero-posterior imbrication confused, mucrones very small ; annuli of frustules flat, finely striate, lines of an antero-posterior imbrication straight and opposite ; silica rather delicate, size variable but always considerable (H. Per.) Marine. — North Sea (Norman). Teignmouth, Devonshire (stomach of Phallusia W. Arn. !) GROUP II. Sqnammosce. — Frustules formed of scales, more or less rhombical, very numerous and giving a squamous appearance to the frustule. We have no form belonging to this group within the limit ol the North Sea. GROUP III. Genuine^. — Frustules formed of rhombical scales arranged usually in two but never exceeding four rows. ANALYSIS OF SPECIES. Valve furnished with a long bristle (seta) . . . . R. setigera. f Mucro long and very robust, curved like a spur . R. Calcar-avis. I f Scales showing coarse inclined Valve furnished »« . . striae, finely divided trans- it, "1 Mucro short, \ J -r, j„t,_j„„+„ J- with a mucro. ■ . ,. ' j versely . . . R. lULDricata. straight, broad. I Scales fine ; puncta in quincunx, visible with difficulty . R. styliformis. Valve with a rather long calyp.tra, attenuate, flattened, without seta or mucro . . . . . . , R. alata. R. setigera Bright w. (Q.J. M.S., 1858, vi., p. 95, pi. 5, f. 6; H.V.H. Atl., pi. 78, f. 6 and 8*), plate 17, fig. 602. Frustule sub-cylindrical, about 5 to 15 times longer than broad, joints only visible in oblique illumination. Striae excessively delicate ; calyptriform RHIZCSOLENIA. 415 process terminating in a very long delicate bristle, generally curved. Breadth of frustule, 1*5 to 2 c.d.m. Usually only fragments of this form are found. Marine. — Rare. Blankenberghr. and basin. Coasts of England (Brightwell, Stolt., Kitton, Norman, Baddelev, Wallick). Scotland (Baxter Coll., No. 2691). Ireland (O'Meara). Kattegat (Cleve). R. Calcar-avis Schultze (Mull. Arch., 1858, p. 339, pi. 13, f. 5-10; Per., p. 113, pi. 4, f. 9-10*), plate 33, fig. 884. Frustules usually solitary, rarely united in threes, cylindrical, of rather large size, with calyptra terminating in'a robust mucro, curved like a spur. Frustules very delicately silicious, with annulation scarcely visible. Marine. — Heligoland (Max Schultze). England (Norman). Ireland (O'Meara). Mr. Peragallo says that this species is wide spread, but that it is overlooked in preparations and is easily destroyed by acids. It is only distinctly visible when its endochronie is present. R. styliformis Brightw, (Q.J.M.S., 185S, vi., p. 94, pi. 5, f. 5 ; H.V.H. Ath, pi. 78, f. 1-5 ; pi. 79, f. 1, 2 and 4* ; Type No. 442), plate 17, fig. 601. Frustules sub-cylindrical, about 6 to 20 times longer than broad, formed of distinct joints, surface covered with decussating strias, about 20 in 1 c.d.m., terminating in a calytriform spathulate process, bifid at the base, the upper part finishing in a straight, stiff process. Breadth of frustule, 2 to 4 c.d.m. Length, very variable. Silica robust. Marine. — Rather rare in Belgium ; Blankenberghe and basin. England (Brightwell, Kitton, Baddelev, Norman, Stolt.). Scotland (Baxter Coll., No. 2691). Ireland (O'Meara). R. imbricata Brightw. (Q.J.M.S., 1858, vi., p. 95, pi. 5, f. 6; H.V.H. Atl., pi. 79, f. 5-6* ; Perag., p. 113, pi. 5, f. 2-3), plate 33, fig. 885. Frustules cylindrical with section elliptical ; calyptra furnished with a small and robust mucro ; annuli covered with coarse stria;, finely divided transversely (analogous to those of the Radioseae) inflected on each side of the median line or pseudo-raphe of the scale ; lines of imbrication lateral, straight, very distant in each pair, silica robust. Marine. — Coasts of England (Brightwell ? Kitton, Norman, Baddeley). Scotland (Baxter Coll., No. 2691), Surface of River Dee (Stolt.). var. Shrubsolii (/?. Shrubsolii Cleve ; H.V.H. Atl., pi. 79, f. 11-13*), plate 33, fig. 886. Only differs from the type-form by its narrower diameter. Marine. — England (Norman, Kitton), Mouth of the Thames (Shrubsole). Excessively common and abundant in the Scheldt. 416 DACTYLIOSOLEN. R. alata Brightw. (Q.J.M.S., 1858, vi., p. 95, pi. 5, f. 8 ; h.v.h. Atl., pi. 79, f. 8*), plate 33, fig. 887. Frustule cylindrical, narrow ; calyptra rather long, much flattened, obtuse, without a mucro, with the line of articulation twisted spirally, showing a small spine at its base. Scales rhombical, finely striate. Marine. — North Sea (Schiitt), Kattegat (Cleve), Yarmouth (Kitton), East Coast of England (Norman). R. Stolterfothii (H. P. Monog., p. 13, pi. 1, fig. 17-18; Encampia striata Stolt.), a cylindrical arcuate form, is met with rather frequently in pelagic gatherings and has been recorded by Stolterfoth from the surface of the Dee, and has been raised by M. Schiilt to the rank of a genus under the name of Henseniella, which the author defines in the following manner : — Henseniella Schiitt, 1893. — Frustule elongated, cylindrical, twisted, recurved, forming spiral chains ; membrane slightly silicious, showing numerous annuliform septa ; valves elliptic, plane, or concave. This genus includes two forms : Henstniella (Pyxilld) Baltica {Hens.) Schiitt and Henseniella Stephanos (Hens.) Schiitt. GENUS 85— DACTYLIOSOLEN CASTR., 1886. Per. em., 1892. Frustules cylindrical, annulate ; valves plane, circular, symmetrical, without spines or processes, sometimes showing a crown of marginal dots. This genus was established by Count Castra- cane for a single form, D. antarctiens represented in the margin (fig. 134). Mr. Peragallo has extended it somewhat so as to admit into it different badly-classed forms, which link the true Rhizosolenia to Melosira. No Dactyliosolen belongs to our regions. Dactyliosolen antarctiens. GUINARDIA. 4^7 GENUS 86.— GUINARDIA, H. Per., 1892. Frustules cylindrical, annulate ; valves circular, showing an undulation ending in an elementary mucro. Fig. 135- Guinardia flaccida. G. flaccida (Castr.) H. Perag. (Monogr. Rhizos., p. 107, pi. h l 3-5)- Frustules cylindrical, valves hyaline, furnished with a small projecting spur, lateral, placed on the summit of an undulation of the valve ; rings flat, hyaline, imbricated in twos ; lines of imbrication oblique, simple and opposite. Diameter, 25 to 80 c.d.m. Silica very slight, frustule completely put out of shape by dessication (H.P.). Marine. — Maritime Scheldt (H.V.H.), Kattegat (Cleve). Peragallo says it is very wide-spread. D D 4i8 I.AUDF.RIA GENUS 87.— LAUDERIA CLEVE, 1873. Fig. 136. Lauderia annulata. Frustules cylindrical, annulate ; valves orbicular, covered, at least near the margins, with numerous filiform processes or spines. The type-form of this genus is Lauderia annulata Cieve, which is figured in the margin (fig. 136), and which inhabits the Java Sea; Lauderia delicatula was found by Stolterfoth, in 1879, on tne surface of the Dee, England. About a dozen other species have been described, but all those hitherto discovered belong to warmer regions than ours. Detonula Schutt (1893), *s a genus created at the expense of Lauderia, for forms with plane valves, without small spines, on the disc surface. PER AG ALLOA. 419 GENUS 87/w.-PERAGALLOA SCHUTT, 1895. Frustules formed of numerous annulate joints, interrupted, with orbicular valves furnished with two long horns, more or less spinous or hirsute. This curious genus, which approaches Aitheya, has the body of a Dac/ytiosokn, and the valves of a Chtetoca-os. It only com- prises a single species. Fig. 137- Peramlloa Meridiana. Peragalloa meridiana Schutt (Ber. Deutsch. Bot. Geseii. 1895, xiii., p. 36, pi. 5, f. 28*). Found pelagic in the Baltic Sea (Schutt). 420 ATT HEY A GENUS 88.— ATTHEYA WEST, i860 Fig. 138. — At they a decora, Frustules cylindrical, annu- late, slightly elongated, flattened; valves elliptic, having a central nodule, and furnished with two bristles at the apices. A single species. Attheya decora, West. (T.M.S., iS5o, viii., p. 152, pi. 7, f. 15* Characteristics of the genus. Marine. — Normandy (Brel). !) England (West), Creswell R. Taylor!), Tynemouth (R. Taylor!), Surface of Dee (Stolt.). Mr. Peragallo, at page 1 1 of his monograph, says : — On the margins of the valve may be seen two lines or sutures, which, parting from the central umbilicus, pass under the bristles, so that the valve in reality consists of two calyptras coupled together. The sutural lines of the frustule follow this direction, and are inflected at their middle. In my opinion, and until otherwise determined, the Attheya ought to be considered as the longitudinal juxtaposition of two Rhizosolenia. It is a transition between a true Rhizosolenia and a C/uetoceros. 1 1. — Eucii.*;tocere/E. — Frustules not consistingof numerous annuli. GENUS 89.— CH^ETOCEROS EHR. (1844). Char, emend. Valves convex, elliptic or circular, furnished with very elongated arms. Frustules generally united into long cylindrical filaments. CH/ETOCEROS. 4-1 Sub-genus I. — Ch.et/OCEROS. Valves elliptic, with awns not arranged in a circle on the margin of the valve. a. b. Fig- 139.— «. Chcetoceros Wighamii. b. Chcetoceros Lorenzianus. ANALYSIS OF SPECIES. Frustules closely united . . . . . . ch. armatum. C Apertures very large, suborbicular ; valves with ■i Frustules leaving horns straight or very slightly curved . Ch, Wighamii, apertures between -J one another. j Apertures longly elliptic, lanceolate ; horns curved I. in the direction of minor axis . . Ch. paradoxum var. Eibenii. Ch. armatum, West. (T.M.S., i860, viii., p. 151, pi. 7, f. i2; H.V.H. Atl., pi. 81, f. 1-4* ■ Type No. 446), plate 18, fig. 603. 422 CH/ETOCEROS. Valve elliptic, having at each apex a long awn, with an obtuse enlarged apex, surrounded at the base with several acute and much shorter awns. Girdle face of frustule elongated, quadrangular. Frustule slightly silicious, of variable size, 3 to 6 c.d.m. in breadth. Mirine.— Found in abundance on the sands at Blankenberghe, where the waves sometimes leave it in the form of long brownish streaks. England (West., Stolt., Kitton). Scotland (Baxter Coll., No. 2888), Holland (Suringar). Ch. Wighamii Brightw. (Q.J.M.S., 1856, iv., p. 10S, pi. 7, f. 19-36; H.V.H. At]., pi. 82, f. 1*), plate 18, fig. 604. Valve convex, oval, covered with small spines, having at each end two very long acute awns. Frustules united into a long filament. Valve (in the specimen observed), 2^5 c.d.m. in length, by 2 c.d.m. in breadth. Marine. — -Very rare at Blankenberghe (2nd Basin). Floiting in the Scheldt ( H.V.H. ). England (Kitton, Stolt., Norman). Ch. paradoxum CI. (Diat. Java, p. 10, pi. 3, f. 16). Valves flat, with raised centre, oval, horns flexed in the direction of the minor axis, very flat, furnished with alternating elevations. Frustules united in a chain, leaving between them two large elliptic oval apertures. Pelagic. — Found floating at Java. Surface of Dee, England (Stolt.). var. Eibenii Grun. (H.V.H. Atl., pi. 82, f. 9, 10*) plate 35, fig. 916. Centre not raised, interfrustular apertures longly elliptic, with lanceolate apices. Length of valve, about 4 c.d.m. Pelagic— North Sea (Eiben). Maritime Scheldt. (H.V.H.). Sub-genus II. — BACTERIASTRUM. — Valve circular, bearing on its margins a circlet of long awns. Ch. (Bacteriastrum) varians Lauder (T.M.S., 1864, iv., n.s., p. 8, pi. 3, f. 1-6; Actiniscus Ehr. ■ H.V.H. Atl., pi. 8o, f. 3-5*; Type No. 445), plate 18, fig. 605. Valve circular, covered with more or less sparse granules, showing a conspicuous median dot, and bearing on its margins a corona of long awns, variable in number, with their ends often undulate, sometimes straight, bifurcated in the individuals forming the median portion of the filament, CORETHRON. 423 simple and more or less curved in the terminal individuals. Frustules united by about 20 in a filament. Marine.— Rare. Blankenberghe, 2nd Basin; ; floating in the Scheldt. (H.V.H.). Stomachs of Noctiluca, Yarmouth (Kitton).' Surface of Dee, England. Common (Stolt. ). East Coast of England (Norman). Note. — The forms for which Ehrenberg constituted the genus Actiniscus were not diatoms, and subsequent authors who have written on these forms have not admitted them in their classification. Ehrenberg included the genus Bacteriastrum in his genus Actiniscus, but without any plausible reason, and he continued to do so until his last work, Fortsetzung dcr Mikr. Studien, 1S75. All the forms of Bacteriastrum ought to be included in the g^nus Chcctoccros (Note by Mr. Kitton). Sub-genus III.— Corethron Castr., 1886. Valves convex, furnished with a corona of erect spines. Frustules cylindrical. As will be noticed, the differ- ence between Bacteriastrum and Corethron' consists in the spines of the first genus being placed horizontally, while in Corethron Fig. 140.— Corethron hispidum Castr. they are erect. Hitherto five species have been described, none of which inhabit our shores. 4^4 DITYLUM. GENUS 90.— DITYLUM BAILEY, 1861. Valve angular, furnished with a long cen- tral spine, with radiant puncta. Frustules distant, slightly silicious, with undulated margins. ANALYSIS OF SPECIES. f Striae excessively fine ; valves not bordered with indentations . . . . D. intricatum. I Striae well marked ; valves bordered with I indentations D. Brightwellii. D. Brightwellii (West) Grun. {Triceratiam Brightwellii, IV-st., T.M.S., 1858, viii., p. 149, pi. 8, f. 1, 5 and 8; D. trigonum and ina-auale Bail. ; Triceratium undulatum, Brightw., Q.J.M.S., 1858, vi., p. 153, pi. 8; H.V.H. At!., pi. 114, f. 4, 8 and 9*; in Type No. 529) plate 17, fig. 606, Valves triangular or tetrangular, with margins straight or undulated, furnished with small spines, somewhat elevated in the centre, and bearing a long spine, surrounded by a small narrow hyaline area; striae radiant (12 in 1 c.d.m. at the margin of the valve), with very distinct puncta. Girdle face with connecting membrane apparently smooth. Breadth of side of frustule about 3^5 to 4*5 c.d.m. Marine. Blankenberghe, rare ; very abundant in some pelagic gatherings from the Scheldt (H.V.H. ). England (W. Arnott ! Kitton), Fig. \\\.—Ditylum Brightwellii. D. intricatum (West.) Grun. {Triceratium intricatum, West., T.M.S., 1858, viii., p. 148, pi. 7, f. 5 ; H.V.H. Atl., pi. 114, f. 2*), plate 17, fig. 607. SYNDETONEl^. 425 Valve triangular with angles elevated, margin triundulate, without indentations ; a rather short spine in the centre ; stria? radiant, very fine, about 20 in 1 c.d.m. at the margin of the valve. Frustules distant, united in a filament. Length of side of frustule, about 6 c.d.m. Marine. — Very rare. Blankenberghe, 2nd Basin. Note. — These two Dityhim are probably forms of a single species. GENUS 91.— SYNDETONEIS GRUN., 1888. ks&* }«#i Valves dissimilar, with two marginal bid- dulphiform elevations, and having in the centre a long horn. The horn of one of the valves with its apex dilated, somewhat bifid ; that of the other valve bifurcate, clasping the horn of the other valve. The genus includes only a single form, S. amplectens (Gr. and Sturt.) Grnn., found in the Oamaru Deposit (New Zealand), and figured in the margin. Fig. 142.- Syndetoneis amplectens {Gr. and Stt/rt. Grun. 426 PYRGODISCUS. Fig. 143. — Pyrgodiscus armatus. GENUS 92.— PYRGODISCUS KITTON, 1885. Valves orbicular, fur- nished with punctate lines, regular, radiant ; showing a high central elevation, usually with eight angles, terminated by the same number of very robust, erect spines ; with margins furnished with eight eleva- tions, each crowned with a short robust awn, alternating with the spines of the central elevation, and connected with it by a ridge, or smooth, elevated line. This genus was created for the fossil form P. armatus Kill., represented in the figure in the margin (fig. 143), which is found in the marl (Tegel) from Briinn, in Moravia, and which is characterised by its size, which attains to 8 to 10 c.d.m. in diameter, while the P. simplex, afterwards created by Dr. O. Witt, is much more delicate, and hardly reaches in diameter the moiety of the preceding. It is found in Simbirsk. Dicladia Ehr., 1844. — Frustule com- pressed, with sutural por- tion narrow, furnished with horns, more or less elongated, often ramous or furcate. Valves sometimes short and obtuse, at other times furnished with short, _ _. . ,. _ . , „. scattered spines. Fig, 144. — Dicladia Caprcolus Ehr. *■ Dicladia Caprcolus (fig. 144 in margin), is the best known species of this genus. It is frequently met with in the living state (amongst others by Mr. Norman, in Ascidinus, off Hull), and in guanos and fossil deposits (Peters- burgh, Naparima, Richmond, etc.). According to the observations of Count SYRINGIDIUM. 427 Castracane, D. Capreolus is only a spore of a Chcetoceros, and consequently should be named C/i. Didadia ( Ehr.) Cast. See Castr. " Challenger," p. Si, pi. 19, f. 7. I include the Thaumatonema of Greville in the Didadia. GENUS 93. — SYRINGIDIUM EHR., 1845. Frustules elongated, with valves furnished with mucronate horns. Valves usually dis- similar, one of them having only a single and the other two horns or processes. The genus includes about a dozen forms ; the S: Awuricanum Bail, represented in the margin (fig. 145), is found in a living state in Brazil, at Trinidad, and in Bengal, and is also found in a fossil state in Fig, i^.—Syringidium the deposit of Nankoori. Americanum Syndendrium Ehr., 1845.— Valves dissimilar, one smooth, the other furnished with numerous elongated spines, often ramous. According to Mr. Cleve and Count Castracane, Syndendrium are only Fig. 146.— Syndendrium Diadema. spores of Chaztoceros. Syndendrium Diadema Ehr., represented in the margin (fig. 146), is found in Peruvian o X! o Frustules cylindrical, with somewhat large regular marginal teeth and a peculiar central clasping spine . Syndetocystis. , r , ... , f Valves furnished with a peculiar hooked central Valve elliptic or sub- du, . Rutilaria, linear, with spines or 1 » ■*•»!.«». marginal teeth, and the \ Valves linear, with median portion inflated, elliptic, ■"fl t h" ? 1°H without any peculiar nodule; linear portion inflated elevated. ^ smooth, with spines, without septa . . Clavularia. I I f Frustules cylindrical ; ends first constricted and finally expanded into a connecting nodule ..... Frustules united by a delicate mucous thread ; valves slightly silicious, having small marginal spines and o Strangulonema. Frustules united into long filaments. radiating dichotomous striation Thalassiosira. j Frustules closely united, ro- ( Frustules and valves bust ; valves circular, very j with cellular structure . Endyctia. silicious, often furnished with -! small teeth at the junction | Frustules and valves of the frustules. { punctate, not cellular . Melosira. f Valves somewhat hyaline and conical or inflated in girdle view, showing costag or ribbed lines in girdle view ; apices often truncate or spinous ; interspaces punctate . Mastogonia Frustules united by twos and threes. Valves apparently hyaline and showing from 3 to 5 mammiform elevations Frustules compressed, subquadrangular elliptic .... Pantocksekia. > o c3 > valve Druridgea. f Valves with areolate margin and hyaline, umbilicate centre . Valves round, convex, like a watch- glass. Margin not arcoate. I I Centroporus. ' Valves regularly striate- punctate throughout the surface . , Podosira. Valves with umbilicate cen- tre, very finely striate, sub-hyaline . , Hyalc-discus. 43° PYXILLA. GENUS 96.— PYXILLA (GREV, 1864), H.V.H. Emend. *Oa a O O O o 3 flB • « 0 6 0 o • »* ^•••-•-•-••3 Fig. 149, Pyxilla Barbadensis. Fig. 150. Kentrodis'cus Huti^aricus . Fig- 151- Pterotkeca aculeifera. Frustules simple, cylindrical, pyxidiform ; valves often of unequal length, showing in the centre a simple or alate apiculus. As we understand this genus, it includes three genera of other authors, which we consider as subgenera only, differing from one another as follows : — ' Apiculus simple . Apiculus covered with small scattered spines _ Apiculus laterally alate and branched . Pyxilla Grev. . Kentrodiscus Pant. . Pterotheca Grun. I figure here Pyxilla Barbadtnsis Grev. (fig. 149), Krtrodiscus Hungaricus, Pant., (fig. 150), and Pterotkeca aculcijera, Grun, (fig. 151). All these forms are fossil. GENUS 97.— KTENODISCUS PANT., 1891. Valves rounded, convex, divided into compartments dichotomously, with margins surrounded by ellip- tic hyaline spaces. Frustules showing in girdle view the valves very inflated, crowned with a comb of alate spines fastened at the base. Fig. 152. — Ktenodiscus Hungaricus. I reproduce (fig. 152) after Dr. Pantocsek Ktenodiscus Hungaricus Pant., a curious fossil form from Hungary, which resembles a Prussian helmet. PEPONIA. 431 The genus also includes Kten. Rossicus Pant., which has been found at Kusnetzk (Russia), which differs from the preceding form by its less developed comb and by the broad hyaline margin of the valve. GENUS 98.— PEPONIA GREV., 1863. Valves inflated, subcircular, with margin abruptly prolonged into a triangular apiculus, obtuse on the two opposite sides. Surface of the valve and of the apiculus areolate. Apiculus with apex raised into a short horn. Fig. 153. — Peponia Barbadensis. This genus only includes one species, P. Barbadensis Grev. (fig. 153), which has been found in Barba- does deposits, Bridgewater (!) and Cambridge Estate. £# * u , s 0 * • « »* t«O0« 0»0#] Fig. 154- Strang u lone ma Barbadensis, GENUS 99.— STRANGULONEMA GREV., 1865. Frustules puncto-areolate, united into a cylindrical filament. Valves constricted near the apices, then spread out and enlarged into a nodule. This genus was created for S. Barbadensis Grev. We reproduce the figure of this author (fig. 154), but in the specimen of this diatom in my possession the constriction is abrupt and not like the neck of a decanter, as designed by Greville. Nor can I recognise the undulated soldering of the adjacent nodules. This very rare diatom is found in the Cambridge Estate (Barbadoes). 432 SYNDETOCYSTIS. GENUS 100.— SYNDETOCYSTIS RALFS. Manuscr., 1864. Valves subcircular, with dentate margins ; having in the centre a cylin- drical process, curved into a hook, which unites the valves to that of the next frustule, and thus produces a filament. We reproduce (fig. 155), after Walker and Chase, Syridetocystis Barbadensis Ralfs, a very curious form, found in the Cam- bridge Estate Deposit, Barbadoes. In the Manuscript for the Fifth Edition of Pritchard, which forms part of my library, Ralfs thus expresses himself : — " Syndetocystis N. G. Ralfs. Frustules as in Biddulphia, but connected in a chain-like manner by strong spines from the centre of their valves. The frustules in the front view resemble those of the p. other genera of this family, except in Syndocystis Barbadensis. having from the centre of each valve a stout central spine, which is suddenly bent near the end and curved in a link- like manner round a similar spine from the adjacent frustule. In the fossil state at least these spines slide upon each other, altering the distance between the frustules, as is well shown in fig. 155, taken from a very perfect specimen belonging to our friend Mr. Norman, of Hull. " S. Barbadensis Ralfn., also from Cambridge Deposit, Barbadoes. Mr. Johnston. " Valves broadly elliptical or suborbicular, with a process near each apex and one or more subulate spines, which are best seen in the front view. Sur- rounding the stout central spine is a large smooth portion, bordered by a circlet of pearly granules, from which radiate rows of granules." RUTILARIA. 433 GENUS 101.— RUTILARIA (Grev., 1863). Emend Grev., 1866. Frustules very compressed, united in a short filament. Valves gently elevated at the angles, with a peculiar central nodule prolonged into two short, linear, obtuse processes. Mar- gins of valve pectinate, ciliate. Fig. 156. — Rutilaria {Epsilon var.) tenuicornis. This curious genus includes about a dozen species, mostly fossil. The figure in the text (fig. 156) represents R. {Epsilon var.) tenuicornis Gr//n., found in a living state at Manilla. GENUS 102.— CLAVULARIA GREV., 1865. Frustules free, linear, elongated, with numerous transverse divisions, an elevation at the median portion and numerous awns. Valves linear, dilated at the median portion, shewing somewhat scattered awns on the surface. A single species, Clavularia Barbadensis Grev., found by C. Johnson in the Cambridge Deposit, Barbadoes (fig. 157). This curious form disconcerts all preconceived ideas, and it is difficult to know where to class it. In the specimens in my possession, the valve is smooth and shows no trace of striation ; the spines are not situated in a straight line, as in Greville's drawing, whose figure we reproduce, but they are scattered on the valve. We give below the description which Greville made of C. Barbadensis. The examination of my specimens, which are unfortunately few in number, suggests a doubt if C. Barbadensis be a true diatom. The following is Greville's description : — " Frustule '0060" to •0080" in length and scarcely "0002" in breadth, perfectly linear, except E E Fig- 157- Clavularia Barbadensis. 434 STEPHANOPYXIS. at the acute apices, having narrow margins, one of them (which I call the upper) strong and coloured. Numerous transverse dissepiments occur throughout the whole length, at irregular intervals, except for a space of about •0014" in the middle, which is occupied by a smooth lamina, folded up, as it were, and pressed against the surface, and so concealing the dissepiments, convex above, where it is on a level with the coloured margin, and gradually tailing off below into the uncoloured margin. Along the upper margin are situated a row of very short stout subcapitate processes, standing up like little nails, at irregular distances, evidently arising out of the substance of the margin itself, and of the same colour, and having no reference to the pseudo-dessepiments. The number of these processes varies ; two generally, but sometimes three or four, belong to the centre, and between the centre and each apex there are from 6 to 9. The valve is the view which occurs most frequently, and strongly resembles a Ceratoneis, there being an oblong inflation or expansion in the middle which passes suddenly into the long exceedingly narrow sub-acute arms. The processes above described appear in the view of the valve as strong, brilliant puncta, seated on one of the margins ; but the puncta which occur in the centre or inflated portion (nearly -0004" in breadth) are situated more or less in the middle of the space and not on the margin." GENUS 103.— STEPHANOPYXIS (£HR, 1844), Char. emend. a. b. Fig. 158. — Stephanopyxis corona. a. Valve. b. Frustule. Frustules cohering by their spines. Valves rounded or elliptic, much inflated, with structure usually cellular, with either a central spine or coronal or scattered spines, very conspicuous. As I understand it, Cresivellia Grev. and Trochosira Kitt are included, according to the above definition, in the genus Steplianopyxis. The species of this genus number more than 30, only one of which, Stephanopyxis Turn's (Grev.), Ralfs {Cresivellia Turn's), H.V.H. Atl., p. 83ter., f. 12*), appears to have as yet been found on the British Coasts. This was found by Stolterfoth on the surface of the Dee, England, and by Norman, in MUELLERIKI.I.A. 435 Ascidians, off Hull. They are all fossil or marine, and inhabit especially the torrid and arctic regions. We give here the frustule (fig. 158^), and the valve (fig. 158,7), of Stcphanopyxis corona (E/ir.), Gntn. (Systephania E/ir.), which is found in the Nottingham deposit. Trochosira mirabilis Kitt., (fig. 159^7), and Trochosira Spinosa Kitt. (fig. 159/;, c), are both found in the " moler " of Mors (Jutland). c. Fig. T59. — a. Trochosira mirabilis h. c. Trochosira spinosa. GENUS 104. MUELLERIELLA, H.V.H., 1894. Valves elliptic, with non-cellu- lar structure, the median portion apparently smooth, with short scattered spines, margins robust, divided into numerous rectangular compartments, formed by the pre- sence of perpendicular costae at the margin. Fig. 160. — Muelleriella limbata. We have pleasure in dedicating this new genus to our friend the Baron and Dr. Ferd von Mueller, the learned explorer of Australia, who for more than twenty years has honoured me by keeping me au courant with his works. M. limbata (Ehr.) H.V.H. {Pyxidicula limbata Ehr., H.V.H. Arl, pi. 83ter, f. 13-14*). Valve elliptic, much inflated, convex ; central portion apparently smooth, but really covered with very fine puncta scattered here and there ; other portions irregularly in quincunx ; numerous robust short spines, bifid or trifid, alate, and anastomosing at the bases. Margins very robust, punctate like the median portion, divided into rectangular compartments, in consequence of the presence of internal costae perpendicular to the margins of the valve. Major diameter of the ellipse, 8 to 10 c.d.m. ; minor diameter, about 4 c.d.m. Fossil. — Sta. Monica (Prep. Weissflog, Nos. 010 and on), Richmond. var. Cristagalli Brun. and Temp. (Diat. Japan, p. 40, pi. 8, f. 8). Girdle face broad and like a hood, having the form of a cock's comb. Limestone from Sendai and Yedo (Brun). 436 THALASSIOSIRA. var. delicatula H.V.H., resembles somewhat ' the preceding variety, but differs from it by the margin in girdle view being narrower, and by the valve having only short simple spines at the central portion, and furnished on the margin with a row of long, slender, recumbent spines. Silica delicate ; puncta scattered, conspicuous ; costae feeble, distant. Fossil. — Sta. Monica (Weissflog, in prep., No. on). GENUS 105— THALASSIOSIRA CLEVE, 1872. Frustules more or less distant, united by a mucous delicate filament ; valves round, slightly silicious, with striation radiant, dicho- tomous, furnished with small submarginal spines. Fig. 161. Thalassiosira Nordemkioldii, This genus only includes R. Nordenskioldii (fig. 161), a delicate species, whose valves are from 2 to 2-5 c.d.m. in diameter, and which is found floating on the surface of the Arctic seas in laige quantities. GENUS 106.— SKELETONEMA GREV, 1865. Frustules cylindrical, united into a filament ; valves inflated, heuri-spherical or digitati- form, with a marginal corona of long teeth or spines, simple or bifurcate at the summit. The genus Skeletonema includes about a dozen species, of which only a single species belongs to our region ; it is the : Fig. 162. Skeletonema mirabile. STEPHANOGONIA. 437 S. Costatum (Grev.) Cleve. {Melosira costata Grev., T.M.S., 1864, i\\, n.s., p. 77, pi. 8, f. 3-6; H.V.H. Atl., pi. 91, f. 4 and 6*), plate 33, figs. 889, 890. Valves slightly silicious, inflated convex, bordered by a corona of long simple, erect, parallel spines. Diam., 1 to 1*5 c.d.m. Marine. — Found floating in the Scheldt, on a level with Hansweert (H.V.H. ). English Coasts : Yorkshire (G. Norman), Teignmouth (Cresswell !). Baltic Sea. Found also in China, Java, and in Peruvian guano. We represent in the text (fig. 162) S. mirabile Gru/i., a very curious species inhabiting Siberia. GENUS 107.— STEPHANOGONIA EHR, 1844 Ch. Emend. Valves somewhat hyaline and conical or inflated in girdle view, with costa? or ribs in valve view ; apices often truncate or spinous ; interspaces punctate. Fig. 163. — Stephanogonia Actinoptyckus. This genus only includes a few fossil species. We represent in the text (fig. 163), Stephanogonia Actinopiychus (E/ir.), (Mastogotria Ehr.), found in the Nottingham deposit. GENUS 108.— PANTOCSEKIA GRUN., 1886. Frustules sub-cylindrical. Valves sub-circular, bearing 3-5 mammiform elevations arranged in a circle. Puncta excessively delicate, giving the valve the appearance of being hyaline, the silica of the valve being much thickened. 433 MELOSIRA. Fig. 164. — Pantocsekia clivosa. The genus includes only a single species P. clivosa Grun., which is found in various deposits in Hungary. GENUS 109.— MELOSIRA AGARDH, 1824. Valves circular, plane or convex, often with small teeth at the junction of the frustules, which are united into a filament of greater or less length. f Fig. 165. — Melosira varians. MELOSIRA. 439 Fig 166. — Melosira sulcata. Fig. 167. — Melosira Roeseana, var. dentroteres. Fisr. 168. — Melosira arena ri a. The species of the genus Melosira are scattered throughout the world. The genus includes a large number of species, which have been divided by various authors into several different genera. Without admitting these genera the Melosira may nevertheless be divided into various groups, viz. : — Gallionella, the valves of which are carinate ; True Melosira without keels, the valves being simply punctate ; Paralia, the valves of which are both punctate and areolate. We represent here Melosira varians Ag. (fig. 165), Melosira (Ortliosira) arenaria Moore (fig. 168), Melosira (Paralia) sulcata (Ehr.) Kiitz. (fig. 166), and lastly Melosira Boeseana Rabh., of which Ehrenberg made a special genus under the name of Liparogyra (fig. 167). 4+° MELOSIRA. ANALYSIS OF SPECIES. I. Valves simply punctate. — MELOSIRA. * Junction surfaces of frustules convex. f Valves with only a slight keel. Frustules globular, Valves with one usually in long bands . . . . M. nummuloides. or two projecting -{ keels. j Valves with two subcorneal keels. Frustules usually (_ solitary or united by two individuals . . . M. Westii. Frustules very robust, breadth usually greater than length, subglobular or disciform, with valves not constricted between the sutural zone and the apices which are strongly convex . . . M. Borreri. Valves without a keel. Frustules constricted between the sutural zone and the apices, which are more or less flattened. Frustule moderately robust, length usually slightly greater than breadth, apices much flattened . M. varians. Frustule slightly robust, length usually greater than breadth, apices very slightly flattened . M. Jurgensii. ** Junction surfaces of frustules plane, often denticulate. i. FRUSTULE SHOWING A SULCUS NEAR THE SUTURAL MARGIN. Frustule robust, broad ; valve showing at the centre some coarse isolated granules . . . . . . M. Roeseana. Frustule more or f Length of frustules usually not much greater than breadth. Valve with rather strong granules M. distans. less narrow, delicate ; valve entirely covered j Length of frustules usually greater than breadth, with granules. [_ Valve with very fine puncta . . . M. crenulata. 2. FRUSTULE WITHOUT SULCUS ON EACH SIDE OF THE CONNECTING ZONE. Frustules very robust, walls very thick, breadth greater than length, finely striate ; disc with costae . . . . M. arenaria. Filamem formed of elongated frustules, with coarse conspicuous granules . . . . M. granulata. Frustule moderately ro- bust ; disc i pjiament formeci 0f short frustules, with granules absent or only very delicate and obscure ; frustule costas. ^ often containing imperfect septa M. Dickiei. II. Valves punctate and areolate. — Paralia. A single form ... . . . M. sulcata. I. Valves simply punctate : MELOSIRA. * Junction surfaces of frustules convex. M. nummuloides (Bory) Agardh. (Syst. Alg., p. 8; H.V.H. Atl., pi. 85, f. 1 and 2*; Type No. 457), plate 18, fig. 608. MELOSIRA. 441 Valve circular, very convex, with a rather elevated keel, covered with concentric, undulated striae ; puncta fine (18 to 20 dots in 1 c.d.m.) ; centre smooth. Frustules globular, elliptic, united in pairs, forming a long monili- form filament. Diameter, about 3 c.d.m. Marine. — Covering the piles of the palisades at Blankenberghe ; England (W. Sm., Norman, Kitton, Arnott, Comber, Stolt.); Scotland (Baxter Coll., No. 2748); Ireland (W. Sm.) ; South Wales (Baxter Coll., No. 2815) ; and on all the Coasts of the North Sea. M. Westii W. Sm. (S.B.D., ii., p. 59, pi. 52, f. 333; H.v.H. Atl, pi. 91, f. 11 and 12*; in Type No. 320), plate 18, fig. 609. Valves circular, strongly convex, with two keels, one marginal, the other near the apex ; external keel surrounded by a circle of puncta in quincunx, in the middle of which, on the internal side of the keel, is found a circlet of coarse beads or small processes, inequally distant, about 2 in 1 c.d.m., excessively fine, centre dull. Frustules globular or subcorneal, solitary or united by twos. Diameter, 3 to 4 c.d.m. Marine. — Blankenberghe, Antwerp (Scheldt); England (W. Sin., Kitton, Comber, Stolt., Nor- man) ; Scotland ; and probably on all the Coasts of the North Sea, M. Borreri Grev. (Hooker's British Flora, p. 401 ; H.V.H. Atl., pi. 85, f. 5-8* ; Type No. 458), plate 18, fig. 610. Valves strongly convex, with coarse puncta, between which are found fine puncta irregularly in quincunx, visible only by oblique illumination, about 20 rows in 1 c.d.m. ; junction-surface hyaline, sometimes showing some isolated dots. Frustules geminate, very robust, breadth usually more than length. Diameter, 2*5 to 4 c.d.m. Sporangial frustules much larger, about 6 c.d.m. Marine and brackish water. — Blankenberghe ; England (W. Sm., Kitton, Comber, Stolt., Nor- man) ; Scotland (Dickie, Arnott) ; Ireland (Arnott, O'Meara) ; and on all the Coasts of the North Sea. M. varians Ag. (Consp., 1830, P. 64; h.v.h. Atl., pi. 85, f. 10, n, 14, and 15*; Type No. 459), plate 18, fig. 611. Valve circular, almost plane, covered with fine puncta, between which are found some coarse dots. Frustules geminate, with fine puncta, intermixed with some coarser dots, with a row of submarginal, distant, coarse beads. Con- necting zone enclosing two frustules, finely striate. Sporangial frustules almost globular. Diameter, 1-5 to 3*5 c.d.m. Fresh water. — Very common throughout Europe. 442 MELOSIRA. M. Jurgensii Ag. (Syst. Alg., p. 9 ; M. subflexilis IV. Sm.; H.V.H. Atl., pi. 86, f. 1-3 and 5* ; Type No. 460), plate 18, fig. 612. Differs from the preceding by its more elongated frustules and its valves more convex, and very constricted near the margins. Brackish water. — Belgium, Holland, England, Germany, etc. ; Scotland (Kitton in Baxter Coll., No. 3846). var. octogona Grun. ! (H.V.H. Atl., pi. 86, f. 9*; in Type No. 460), plate 18, fig. 613. Connecting zone with blunted angles. Brackish water. — Austruweel near Antwerp. Mixed with the type-form. ** Junction surfaces of frustules plane, often denticulate. I.— FRUSTULES SHOWING A SULCUS AT THE SUTURAL MARGIN. M. Roeseana Rabenh. (Alg., Nos. 383 and 504, Sussw. Diat, pi. 10; Oithosira spinusa //'. Sm. ; H.V.H. Atl, pi. 89, f. 1-6*; Type No. 465), plate 19, fig. 614. Valves circular, with striae radiant, punctate, puncta becoming more and more fine towards the centre, which is hyaline, and furnished with two to five coarse granules; striae on the margin of the disc about 7 in 1 c.d m. Frus- tules with valves constricted towards the disc, whose margins are denticulate, and having near the sutural margin a broad and deep sulcus. Connecting membrane very finely striate, about 21 striae in 1 c.d.m. Diameter of valve, 1 '25 to 4*5 c.d.m. Sporangial frustule almost spherical. On moss, etc. — Frahan (Delogne), France (De Br£b. ), England (W. Sm.), Scotland (Kitton in Baxter Coll., No. 3850), Ireland (O'Meara). var. spiralis (Liparogyra spiralis Ehr. ; H.V.H. Atl., pi. 89, f. 7 and 8*; in Type No. 465), plate 19, fig. 616. Frustules narrow and very elongated, furnished internally with a spiral band transversely striate. With the preceding. — Very rare. Norwich, England (Kitton). M. distans KlitZ. (Baa, p. 54, pi. 2, f. 12; H.V.H. Atl., pi. 86, f. 21-23*; Type No- 46l)> plate 19, fig. 616. Valve circular, with sparse, rather strong puncta. Frustules with very thick valves, sulcus rather broad, but very deep. Striae, 14 in i c.d.m. Fresh water. — Hatrival (Del.). Found throughout Northern Europe. MELOSIRA. 443 var. nivalis (W. Sm.), (Coscinodiscus minor W. Sm. nee Ruiz.; H.V.H. Atl., pi. 86, f. 25-27* ; Type No. 462), plate 19, fig. 617. Valve with stronger and more approximate puncta. Marine. — Scotland (Baxter Coll., No. 2699). M. crenulata Klltz. (Baa, p. 35, pi. 2, f. 8 ; M. orichalcea IV. Sm. ; H.V.H. Atl., pi. 88, f. 3-5* ; in Types No. 401, 481, etc.), plate 19, fig. 618. Valve with finely punctate disc, puncta scattered, margins showing numerous well-marked denticulations. Frustule much longer than broad, showing on the margin of the valves a slightly marked sulcus, striate, with striae generally somewhat oblique, about 18 in 1 c.d.m., consisting of some- what elongated puncta. Diameter, "67 to 2-0 c.d.m. Fresh water. — Probably not rare. Found throughout our regions. forma tenuis (M. tenuis Kutz. ; H.V.H. Atl., pi. 88, f. 9 and 10*), plate ig, fig. 619. Differs from the type-form by the greater length of the frustules and smaller diameter, which does not exceed '5 c.d.m. Fresh water. — Lake in Park at Antwerp (H.V.H., Type No. 190). forma Binderiana (M. Bindcriana Kutz. ; H.V.H. Atl., pi. 88, f. 16*), plate 19, fig. 620. Frustules excessively elongated. Length equal to 5-8 times the diameter. Fresh water. — Rouge-cloitre (Delogne). All these forms are sometimes met with in the same gathering and even in a single filament ; they are therefore only forms deserving of being ranked as varieties (Kitton). 2. FRUSTULE WITHOUT A SULCUS ON EACH SIDE OF THE CONNECTING ZONE. M. arenaria Moore (in Raifs Ann., xii., pi. 9, f. 4 ; H.V.H. Atl., pi. 90, f. 1, 2 and 3*; Type No. 468), plate 19, fig. 621 (left-hand figures). Valve with very thick walls ; disc furnished with costse, which add to the breadth and height, from near the centre to the circumference, where they simulate spines ; centre slightly depressed and covered with puncta ; costae about 6 in i c.d.m., fitting perfectly with those of the adjoining disc. Frustule broader than long, finely striate ; stria? punctate in quincunx (about 18 longitudinal rows in i c.d.m.). Valve with sutural margin furnished with costae on its thickened portion, and of which the apices fit together and simulate two rows of beads. (In fig. 1 of H.V.H. Atl., pi. 90, these rows of 444 MELOSIRA. beads are, in error, drawn separated ; they should touch one another). Diameter, 6 to 10 c.d.m. In humid mosses, &c, rare? — Alle (Delogne) Schooten near Antwerp (H. Van den Broeck), England (W. Sin., Kitton, Arnott, Norman), Scotland (Greville), Ireland (Dickie, O'Meara). M. granulata (Ehr.) Ralfs. (in Pritch., p. 820; h.v.h. Atl., pi. 87, f. 10-12* ; Type No. 463), plate 19, fig. 621 (right-hand figures.). Valve disc with large granules, scattered, distant, slightly marked, margin much indented. Frustules elongated, with valves marked with very coarse, strongly marked granules, arranged in longitudinal lines, 7 to 9 in 1 c.d.m. Diameter, "5 to 175 c.d.m. Freshwater. — Brussels, Antwerp, rare? France, England. var. curvata Grun. (H.V.H. Atl., pi. 87, f. 18*), plate 19, fig. 622. Valves very long, filament very narrow, curved. Fresh water. — Antwerp. Mixed with type-form. M. Dickiei (Thwaites) Kiitz. (Spec Aig., p. 889 ; Onhosha Dickiei Thw. ; H.V.H. Atl., pi. 90, f. 10, 12, 15 and 16* ; Type No. 469), plate 19, fig. 623. Valves with fine granules only occupying the central portion. Frustules short, with very fine puncta and a row of stronger puncta through the length of the connecting zone. Typical frustules are often mixed with other elongated, elipsoidal frustules, formed of several individuals incompletely par- titioned, emboxed one in the other. Diameter, 1-25 to 175 c.d.m. Length of typical frustules, 1*25 to 2-5 c.d.m. and of partitioned frustules up to 5 to 6 c.d.m. Fresh water.— Very rare. ? Frahan (Delogne), Scotland (Dickie !), Ireland (O'Meara). II. Valve punctate and areolate : Paralia. M. Sulcata (Ehr.) KlltZ. (Baa, p. 55, pi. 2, f. 7 ; Orthosira marina IV. Sm. ; Paralia sulcata Heib. ; H.V.H. Atl., pi. 91, f. 16*; in Types Nos. 470, 490, etc.), plate 19, fig. 624. Valve disc bordered with a series of coarse beads, alternating with a series of smaller and more or less visible beads, and of a broad circle of fine puncta in quincunx. Central portion entirely hyaline (var. genuina Grim) or having round the hyaline centre a series of fine radiant costse of greater or less length (var. radiata Grun.). Frustule showing at the sutural margin a series of large elongated alveoles, followed by smaller alternating alveoles. Diameter, 3 to 5 c.d.m. Marine.— Rather rare. Blankenberghe, Antwerp (Scheldt) ; England ! (Brightwell, Kitton Capron, Oliver, Stolt., Norman) ; Scotland (H.V.H., Type No. 101) ; Ireland (W. Sm., O'Meara). Probably should be found on all the Coasts of the North Sea. ENDVCTIA. 445 GENUS 110.— ENDYCTIA EHR., 1845. Frustules cellular, simple, or forming a short filament. Valves circular, reticulate, or areolate, with raised denticulate margins. The genus Endyctia is related on one side to Stephanopy.xis and Melosira, and on the other to Coscinodiscus. We represent in the text (fig. 169) Endyctia Fig. 169. — Endyctia oceanica. oceanica Ehr., found in Peruvian guano, and found also by Dr. Pantocsek in a fossil state in Hungary. The genus includes about a dozen species, all of which (with the exception of Endyctia Campeclriana Grun.) have been found in Hungary. GENUS 111.— CYCLOTELLA KUTZ. 1833. Valve disc divided into two portions, the exterior annular, with striae smooth (costae) or punctate, more or less fine, sometimes inter- mixed with small spines ; always without a pseudo-nodule ; centre often bullate, smooth or granular, with granules sparse or radiating. Girdle face straight or undulate. Frustules not united in a band. ' Some fifty Cyrfotdla have been described or named. These diatoms are spread over the whole world, and are found in a fossil state as well as living ; a considerable number of species are small and the greater number have undulated valves ; they are especially differentiated from Melosira by never being joined by long bands, but, at most, are only found united by two or three individuals. The species figured in the text is Cyclotella Kiitzingiana var. Schumanni 'Grun. (fig. 170.) Fig. 170. Cyclotella Kiitzingiana var. Schumanni. 446 CYCLOTELLA. ANALYSIS OF SPECIES. Valve with margin strongly striate, with centre coarsely punctate and usually near the margin of the latter a demi-circle of coarse puncta . C. striata. f Valve having in the central portion a rosette of elevated triangu- lar dots . . . . . . C. antiqua. o a o a a > I Valves without elevated triangular dots. f Marginal stria; intermixed with much stronger striae, at regular distances . . . C. comta. L Marginal striae intermixed with small All the striae equally well marked. spines Striae without small spines. C. operculata. f Marginal striae very ro- bust ; puncta radiant . j Marginal striae feeble ; "i centre with fine scat- tered puncta some- times mixed with some C. Meneghiniana. coarse dots C. Kutzingiana. C. Striata (Kiitz.) Grun. (Coscinodiscus striates Kutz.; Cydotelia Daliasiana W.Sm. ; H.V.H. Atl., pi. 92, f. 6-10* ; in Type No. 320; var. stylorum, Type No. 474), plate 22, fig. 651. Valve with margin strongly striate, centre coarsely punctate, puncta scattered. Centre often bordered with a semi-circle of more distant puncta ; 7 to 12 costae in 1 c.d.m. at the margin of the valves. Diameter, 3 to 8 c.d.m. Marine.— Antwerp (Scheldt, H.V.H. ), England (Dallas, Kitton, Norman). C. antiqua W. Sm. (S.B.D., i., p. 28, pi. 5, f. 49; H.V.H. Atl., pi. 92, f. 1*), plate 22, fig. 652. Valves with well-marked marginal costae, intermixed with spines or coarse dots, centre finely granular, with 6 to 15 triangular elevations. Diameter, 1*5 to 3 c.d.m. Fresh water. — Not yet found in Belgium. England (Norman) ; Western Islands (Baxter Coll., Nos. 2733, 2734) ; Peterhead Deposit (Baxter Coll., No. 2737); Aberdeen Deposit (T. and P., No. 443) ; Ireland (W. Sm.) ; Norway, Finmark, &c. C. COmta (Ehr.) Kutz. (Spec. Alg., p. 20 ; Discoplaa comta Ehr. ; H.V.H. Atl., pi. 92, f. 16-22* j in Type No. 424), plate 22, fig. 653. Valve with well-marked marginal costae, each third or fourth costae being much more vigorous than the others ; central portion finely striate, striae punctate or more or less radiant. Girdle face somewhat inflated in the middle. Frustule plane, not undulated. Diameter, 75 to 3 c.d.m. Fresh water.— Antwerp (H.V.H.), England (Kitton). podosira. 447 var. radiosa Grun. (H.V.H. Atl., pi. 92, f. 23, and pi. 93, f. 1-9*; in Type No. 475), plate 22, fig. 654. Larger than the type-form, with centre showing punctate striae distinctly radiant. Attaining as much as 4 c.d.m. Not yet found in Belgium. Scotland (H.V.H. , Type No. 475). C. Operculata KlitZ. (Baa, p. 50, pi. r, f. i, 12 and 15 ; H.V.H. Atl., pi. 93, f. 22-28* ; Type No. 476, var. mesoleia), plate 22, fig. 655. Valves with rather marked marginal costs, intermixed with small spines arranged regularly. Centre finely punctate, puncta scattered {var. mesoleia Grun.) or radiant (var. radiosa Grun.). Girdle face undulate, 16 or 17 costas in 1 c.d.m. Diameter, 1*25 to 3 c.d.m. Fresh water.— Not yet recorded in Belgium, but found in France, England (Kitton, Comber, Norman), Ireland (Dickie, O'Meara). C. Meneghiniana Kiitz. (Baa. p. 50, pi. 30, f. 68 ; C. Kutzing- iana IV. Sm. f \ H.V.H. Atl., pi. 94, f. 11-13*; in Type No. 478; forma minor: Type No. 479; var. redangulata Bred.: Type No. 480), plate 22, fig. 656. Valve with robust marginal striae, delicately punctate, transversely ; centre with fine radiant dots and one or two coarse dots placed almost in the middle of the ray. Girdle face undulated. Striae, 7 to 9 in 1 c.d.m. Diameter, 1 to 2 c.d.m. Fresh water.— Antwerp, Holland, England (Kitton, Norman), Ireland (O'Meara). C. Kutzingiana Chauvin. (H.V.H. Atl., pi. 94, f. i, \ and 6* ; Type No. 477), plate 22, fig. 657. Valve with fine marginal costae, centre very finely punctate, puncta scat- tered, with sometimes i to 3 coarse isolated dots. Girdle face strongly undulated. Striae, 12 to 14 in 1 c.dm. Diameter, 1-25 to 2-5 c.d.m. Freshwater. — Antwerp, and probably in many other localities in Belgium; Falaise (Fiance, Breb. !) ; England (various localities : Thwaites, Norman, Kitton, Comber, Shadbolt, W. Arnott, etc.) ; Scotland (Baxter Coll., No. 2530) ; Ireland (O'Meara). GENUS 112.— PODOSIRA EHR, 1840. Valves very convex, hemi-spherical, finely punctate or subareolate, puncta extending regularly throughout the valve. Frustules stipitate, solitary, or united by 2 or 3 by means of a gelatinous neck. Fig. 171. — Podosira Adriatica. Marine. 448 DRURIDGEA. The genus Podosira only comprises living diatoms, or those found fossil in deposits of marine origin. There are about 20 species, none of which belong to our regions. The form represented in the text (fig. 171), is Podosira Adriatica {Kuiz.) Cntn., which lives in the Adriatic. GENUS 113.— DRURIDGEA DONK, 1861. Only differs from Podosira by its elliptic valves and more compressed subquadrangular frustules. Fig. 172. — Druridgea geminata. This genus only comprises a single species, D. geminata Donk. (Q.J. M.S., 1861, i., n.s., p. 13, pi. 1, f. 15 ; H.V.H. Atl., pi. 91, f. 25, 26*), represented in the text (fig. 172), and which has been found in various localities in England: Cresswell Sands (W. Arnott !) ; Tynemouth, Northumberland ; Druridge Bay, Yarmouth Sands. We have never met with it on the Belgian shores, but it will probably be found there. It is always found on the sand of the sea- shore in frustules united in twos. GENUS 114.— HYALODISCUS EHR., 1854. Valve orbicular, with a very dis- tinct and finely-marked umbilicus, furnished with rays or decussating lines. Fig. 173. — Hyalodiscus Stelliger. The Hyalodiscus are not essentially different from Podosira except in the umbilicus, which is more or less distinct according to the species. The genus includes about half a dozen very characteristic species, some living, some fossil, only two of which inhabit our regions : H. Stelliger Bail. (fig. 173), and H. subtilts Bail. var. Scoiica. CENTROP0RUS. 449 { ANALYSIS OF SPECIES. Valve apparently divided into compartments, striation very distinct . H. stelliger. Valve not divided into compartments, striation extremely delicate . H. subtilis. H. subtilis Bail. (New spec, 1854, p. 10, f. 12; CI. and Moll. Diat., No. 2, sub. H. Franklini E.) Valve orbicular, convex, not apparently divided into compartments ; umbilicus, very distinct, coarsely punctate, with irregular, jagged margins. Valve apart from the umbilicus, apparently hyaline, with very delicate structure, puncta in lines crossing one another, forming 24 to 26 striae in 1 c.d.m. at the median part of the valve, and attaining as much as 30 at the extreme marginal portion. Diameter, 2 to 10 c.d.m. Marine. — Authors have not recorded the large form from our regions, but I have found rare specimens, possibly reaching there accidentally, not only on the Belgian coast (Blankenberghe), but also in the mud of the Scheldt. The smaller form inhabits our country, and has been recorded from Scotland, North Wales (Stolterfoth), and has been described under the name of H. scoticus [Kiitz] Grun. ! (= Cyclotella Scotica Kivtz. in Coll. H.V.H. ; H.V.H. Atl., pi. 84, f. 15-18*), plate 35, fig. 917 ( : 600). H. Stelliger Bail. (New Spec, 1854, p. 10; Podosira maculata IV. S/n. ; H.V.H. Atl , pi. 84, f. 1,2*; Type No. 454), plate 22, fig. 650. Valve orbicular, apparently divided into a large number of compartments. Umbilicus very distinct, finely granular, with irregular margins often laciniate, prolonged so as to form the margins of the compartments. Valve with granules arranged in quincunx, forming about 16 lines in 1 c.d.m. Diameter, 3-5 to 8-5 c.d.m. Marine. — Frequent : Blankenberghe, Ostend, Heyst, Antwerp (Scheldt). England : Norfolk, (Kitton); Surface of Dee, (Stolt.) ; Hull (H.V.H., Type No. 529). Bahnsea. Probably found on all the coasts of the North Sea. GENUS 115— CENTROPORUS PANT., 1889. Valves convex, orbicular, with broad margin decorated with small arcuate compartments, striolate and separated from the disc by a hyaline annulus. Disc punctate, with fine puncta arranged in radiant rows, centre rounded, with- out puncta. This genus only comprises a single form, C. crassus Pant., which we repro- duce here (fig. 174), and which has been Fig. 174. — Centroporus crass its. found in a fossil state at Ananino in Russia. v F Tribe XXI. — Biddulphie/E. f Valves unlike ; frustutes with one neck-like process, generally oblique, cohering irregularly . d > f r "> ti S ^ £ W) 3 Wl ._ r- O 9-? d .3 in proc str narg s ob __>>-!) • - d "3 .5 d w usu ern; met a) s o t/1 ^3 •— e w u • — ' ^ ^ 3 XJ.b SsSM g Si d cu Ph o g.~ r 0) '5 in a; o d ■q C ^2 ■3 3 d > Frus- tules scarcely silicious. o d o d > Valve oval, elliptic. Apices raised on the j major ] diameter Apices terminating in a hood Apices ter- ( Processes of equal length minating in a j point or "i, Processes of unequal length 1, mucron. (_ frustules cuneate I Margins r: [_ distinct v aised on the minor diameter umbilicus valve with small v , , f Valve triangular, furnished with three processes L 3 ' v. Valves quadrangular, furnished with four processes Apices not raised, no mucron ; valve oval elliptic Apices with capitate [ Valve linear-lanceolate, with several constric- septa in girdle view, tions , d a e 5 •> a - O m in and resembling musical notes. Valves with scalari- form septa. v Valve with three processes like nipples a! > Frus- tules and valves not as above. r Valves not arcuate. Valves composed of numerous joints, cells, or pseudo-cells ; gradually diminishing from the median, which is very large Valves elliptic or with straight apices Valves vermiform, sigmoid Valves arcuate .... ' Valves triangular, septa numerous, in the centre of the valve a triangular figure, with different striation .... Isthmia. Baxteria. Hemiaulus. Corinna. Graya. Trinacria. Solium. , Ploiaria. Terpsinoe. Hydrosera. Pseudo-Rutilaria. Auaulus. Helminthopsis. Eunoiograrunia Septa not scalari- form. Valves not triangu- lar, septa few. Valves oblong, with inflated centre, and apices raised into obtuse processes i | Valves arcuate, with 2-3 septa, some- times absent or obscure. Puncta (_ very coarse, radiant . , d C r Valves elliptic circular, 3, 4, or 5 angular, etc., having elevated obtuse pro- cesses at the apices and sometimes also simple horns ' Valves elliptic, showing four elevations and transverse and radiant hyaline spaces (canaliculi ?) . f Valves showing 7-8 elevations, mammiform and marginal .... 2 a -[ a a I in V > "d > Valves not as above. Valves not as above. Entogonia. Porpeia. Euodia. Biddulpnia Tabulina. Grovea. Valves showing two elevations alternating with ocelli . . . . . Huttonia. Valves furnished with spinous ridges Odontotropis. fur- often bifurcated, horns Keratophora above • 1 peculiar I I. horns. L Filament twisted round itself like a cork-screw.- Valve without processes nished 1 with j Valves bearing long peculiar I horns, terminating in horns. I cup-shaped expansion Filament not twisted spirally. Frustules with processes short, obtuse ; valves without awns. f Valves with two ( Filament curved spirally I processes obscure < or absent. I Filament straight Valves with three processes, filament straight I. Frustules furnished with robust awns , , Kittonia. Streptotheca. Eucampia. Climacodium. Bellerochea. Lithodesmium. ISTHMIA. 451 I. Isthmie.e. — Frustules with valves alike, furnished with a neck-like process. GENUS 116.— ISTHMIA AG., 1830. Frustules compressed trapezoidal, with valves furnished with a neck-like process, usually oblique, cohering irregularly. ANALYSIS OF SPECIES. Valves furnished with nerves or interior costre Valves without interior costas I. nervosa. I. enervis. Fig. 175a:. — Isthmia Enervis. Girdle view. I. enervis Ehr. (inf., p. 209, pi. 16, f. 6 ; h.v.h. Atl., pi. 96, f. 1-3*; Type No. 486), plate 19, fig. 625. 452 TERPSINOE. Valve oval, elliptic, with coarse cells irregularly hexagonal placed in rows radiating round a group of central cells ; cells of process diminishing gradually in size up to the end. Girdle face elongated, trapezoidal, with conspicuous process, valve portion having 1*5 rows of cells in 1 c.d.m. Connecting membrane with cells in regular longitudinal rows, smaller than those of the valve, about 2*5 rows in 1 c.d.m. Length of valve, 5*5 to 2 1 c.d.m. Fig. 175^. — Isthmia enervis. Valve view. Marine, parasitic. — Very rare in Belgium, and hitherto only found ill the washings of mussels. England (W. Sin. ! Ralfs, Kitton, Mrs. Griffiths, Okeden) ; Ireland (W. Sm„ Dickie) ; Channel Islands (Baxter Coll. No. 3825); France (Desmazieres) ; Finmark and Spitzbergen (Cleve). I. nervosa Kutz. (Baa, p. 137, pi. 19, f. 5; W. Sm, S.B.D., ii., p. 52, pi. 47* ; H.V.H. Types, No. 485), plate 34, fig. 891. Differs from the preceding by interior costas, which consolidate the valve and are very visible in the girdle face. Marine. — Parasitic on other algae. Not yet found in Belgium, England (W. Sm. ! Kitton). Ireland (O'Meara, Mrs. Lvon, Moore). Shetland Islands (Edmonstone), Denmark. Iceland (C. Agardh). II. Hemiaulide^e. — Valves sim- ple or septate, often showing various abnormal inflations or with apices raised into a mucronate point. GENUS 117.— TERPSINOE EHR., 1843. Valves furnished with transverse costse, without spines or any trace of pseudo- raphe. Frustules showing in girdle view transverse costae, capitate, resembling musical notes. Frustules united in bands. a. Fig. 176. Terpsitw'e music a. a. Valve view. b. Girdle view. HYDROSERA. 453 My genus Terpsino'e comprehends the genus Pleurodesmium Kutz, 1S46, which is only differentiated by the frustules being united by the intermediary of short processes in the form of feet, and also the genus Telragramma Ekr., 1843, which has as its unique characteristic, the possession of valves with fine costae. *<&*. e. . Fig. 182. — Hemiaulus bifrv/is. a. Valve view. l>. Girdle view. a. b. Fig. 183. — Trinacria Negri i a. a. Girdle view. /». Valve view. b. c. Fig. 184. — Solium exculptum. a. Girdle view. /'. Valve view. c. Filament. PLOIARIA. 457 b. Fig. 185. — Corinna elegans. a. Valve view. b. Girdle view. t. Filament. The true Hemiauhts, of which more than 70 species are recorded, is rarely found in a living state. Some few species, such as H. Heibergii, meinbranacea and Hauckii have been so found in the Java Sea and the Adriatic, but the remainder are fossils, the greater number being found in the deposits of Mors, Baibadoes, Simbirsk, Oamaru, &c. The true type-forms belonging to the three other sub-genera have not yet been found elsewhere than in the deposit of the Island of Mors. The Hemiaulus are large diatoms with strong silica ; they form very interesting objects when viewed as a dry preparation with dark ground illumination under a low power objective and a binocular microscope. This is the best means which a beginner can employ in order to obtain a good idea of what a diatom really is. GENUS 122,-PLOIARIA PANT., 1889. a. b. Fig. 186. Ploia ria peiasiform is. a. Girdle view. b. Valve view. Valve lanceolate, elliptic, with apices broadly rostrate, puncta well marked and distinct, valve convex in prirdle view and median portion abruptly inflated, almost hemispherical. A single species. 453 GRAYA. Ploiaria petasiformis Pant. (Batill. Mag., I., 1886 ; p. 48, pi. 29, f. 295, sub Hemiaiilo ; II., 1889, p. 83, pi. 28, f. 403, 405), represented in the text (fig. 186). Dr. Pantocesk has found this form in the deposits of Hungary. The valve is about 5 to 6 c.d.m. in length, and about 2-5 c.d.m. in breadth. GENUS 123 —GRAYA BRUN & GROVE, 1892. Fig. 187. Graya Argonauta. a. Girdle view. b. Valve view. Valve broadly elliptic, with margin much elevated near the median portion. Centre umbilicate, often surrounded with a small area sometimes linear narrow, at other times subrhomboidal. Striae delicate, finely punctate, radiating round the umbilicus. Girdle face very broad, appearing to be undulate in consequence of the margin of the valve being elevated ; connecting membrane very delicately punctate, Frustules united into very short filaments. A single species : — Graya Argonauta Br. and Gr. (fig. 187), after Professor Brun's specimen. This form, which has only been found and named since 1892, appears to have escaped the observation of diatomists, since it is not excessively rare. It has been found in the fossil deposits of Maryland (Brun !), Sta. Monica (Thum. !), and Oamaru (Weissflog). In the specimens from Maryland the median area is elongated ; in those I have from Sta. Monica, it is rhomboidal, and lastly, it is absolutely wanting in my specimen from Oamaru. PSEUDO-RUTILARIA. 459 m -'-4i UN r GENUS 124.— PSEUDO- RUTILARIA, Grove and Sturt, 1886. Valves furnished with spines, con- sisting of 8 to 12 cells or loculi, circular or subcircular, somewhat apiculate laterally at their median portion, arranged in a longitudinal series, the median cell very large, the others decreasing gradually. Girdle face subrectangular, showing the median cell inflated and the terminal prolonged projecting. Frustules united many together, and cohering by the terminal cells and by the spines of the median cell. A single species. a. b Fig. 188. — Pseudo-Rutilaria monile. a. Valve view. /;. Girdle view. P. Monile Gr. and St., represented in the text (fig. 188), and which is found in the Oamaru deposit (New Zealand). Messrs. Grove and Sturt think that Rutilaria recens Cleve should be added to this genus. In my opinion the latter form differs from the Rutilaria, especially by the absence of the peculiar nodule and from the Pseudo-Rutilaria by its unique cell. This form appears to me to be intermediate between the two preceding genera, and I shall therefore make a special genus, to which I give the name of GENUS 125.— RUTILARIOPSIS, H.V.H., 1894. Valves elliptic, with apices diminuate, prolonged, raised into a point ; surface with strong puncta, distant, scattered, intermixed in the median portion with some strong spines. Margin of valve furnished with a circlet of spines. Girdle face very slightly convex from the apices towards the median portion ; apices raised into a point and spines marginal. A single species, represented in the text (fig. 189), Fig. 189. — Rutilariopsis tecens. 460 l'.AXTERIA. Rutilariopsis recens (Cleve) H.V.H. {Rutiiaria recens Clere. On some new or little known Diat., p. 19, pi. 4, f. 57,; H.V.H. Atl. pi. 105, f. 9). Length, 3-5 to 10 c.d.m. Breadth, 15 to 2-5 c.d.m. Characteristics of genus). Inhabits the Galapagos Isles (Eugene Expedition ; Weissflog). GENUS 126.— BAXTERIA, H.V.H., 1893. Valve very elongated, with median portion subrhomboidal, very gently attenuated up to the apices, which are inflated-rounded, with punctate subareolate structure. Girdle face flattened, showing numerous elongated spines, which edge the valve. The two apices terminated by a species of cap, large, very projecting, with strong puncta. a. b. Fig. iqo. Boxteri a Brunii. a . Girdle view. b. Valve view. I have dedicated this very curious and strongly marked genus to my kind and learned translator, Mr. Wynne E. Baxter, as a slight evidence of my recognition of all the trouble he has taken, and the sacrifices he has made, in the publication of the English Edition of this work. Baxteria Brunii, H.V.H. Characteristics of the genus. Length of valve, 5 to 5.5 c.d.m. Breadth at the median portion about 1.5 c.d.m. Fossil, — Cambridge Estate, Barbadoes (E. Weissflog). In the unique preparation in my possession of this interesting form, the valves were disarranged and placed aslant, rendering it difficult either to design or photograph. Before attempting to return it (which I ultimately succeeded in doing) to a convenient position for photographing, and which attempt, if unsuccessful, might have caused its destruction, I solicited my friend Professor Brun to assist me, with his great talent as a draughtsman, in order that a satisfactory representation of it might be produced, and I have therefore felt it but my duty, while thanking him for his kindness, to dedicate the species to him. The figure in the margin, therefore, is a combination of the drawing of Professor Brun and the photograph which I subsequently made of it. EUCAMPIA. 461 III. Eucampie.k. — Pelagic diatoms, with frustules slightly silicious. GENUS 127.— EUCAMPIA EHR. (1839), Char, emend. Frustules imperfectly sili- cious, cuneate, united in a spiral filament. Valve elliptic, with process slight or absent. Fig. 191. — Eucampia Zodiacus. ANALYSIS OF SPECIES. Valves apparently excavated in the girdle face Valves plane, not excavated .... E. Zodiacus. E. Britannica. E. Zodiacus Ehr. (Kreideth, p. 71, No. 41, pi. 4, f. 8 ; H.V.H. Atl., pi. 95, f. 17, 18* ; pi. 95 bis, f. 1 and 2*), plate 19, fig. 628. Valve elliptic, rising gently towards the apices so as to form two robust rounded processes, furnished with a central pseudo-nodule, striae delicate, radiant, finely punctate, above 16 to 18 at the margin of the valve. Girdle face cuneate, at the valve portion striate, with connecting zone showing some longitudinal plicae. Length of valve, 4 to 5.5 c.d.m. Frustules united into a perforated filament. Marine.— Rare. Blankenberghe 2nd Basin. In June, 1893, while engaged in pelagic dredging in the Scheldt opposite Hansweert I found this Eucampia in considerable quantity. Some of these were good specimens, being joined in a spiral filament of more than one complete whorl. England (Kitton, Comber, W. Sm. ! Stolterfoth !), France (De Breb.), Holland (Suringar), near Cuxhaven (Kiitz.). E. Britannica W. Sm. (S.B.D., ii., p. 25, Pl. 61, f. 378*), plate 34, fig. 893. Valves plane, frustules united into a continuous filament, not excavated. Marine. — Sussex, England (W. Sm.), Yarmouth (Kitton). Molleria cornuta Cleve. (f\g. 192) is a true Eucampia; it is characterised by its valves being excessively excavated, and by the apices of the valves being consequently prolonged into horns. Fig. 192. — Moileria cornuta. 462 CLIMACODIUM. GENUS 128.— CLIMACODIUM GRUN., 1868. Frustules straight, slightly silicious, united into long per- forated chains. Valves with apices elevated, of equal length. Clima- codium differs from Eucampia in the frustules being straight, and consequently the chains also are not curved spirally. Only one species of this genus has been described CI. Frauenfeldianum Griin. (fig. 193), which was found by Frauenfeld near Tilan Shong. Fig. 193- Climacodiu m Fra uenfeldian it in . STREPTOTHECA. 463 GENUS 129.— STREPTOTHECA CLEVE, 1890. 7 O C??rfc> ft/ '°oo°o o o o Or? OoOO OO^C>oC 00 c pet 0 O 0O«Q° Fig. 194. — Streptotheca Tamesis. Frustules not silicious, forming a long flat ribbon, twisted on itself at regular intervals. One species : — 464 BELLEROCHEA. StreptOtheca Tamesis Cleve (in Shrubsole "On a new Diatom in the Estuary of the Thames," J.Q.M.C., 1890, iv., n.s., p. 259, pi. 13, f. 4-6). Marine. — In the Thames at Sheerness-on-Sea (Shrubs. !). This curious form, of which, in consequence of its fragileness and transparence, no durable preparation has hitherto been made, must be accepted as a diatom with caution, as the arrangement of the endochrome alone enables us to rank it with diatoms. Further study should be able to determine the question. GENUS 130.— BELLEROCHEA. H. VAN HEURCK, 1885. Fig. 195. Bellerochea Malleus. Frustules scarcely silicious, united into a long narrow filament, leaving elliptical open- ings between one another. Valve triangular or quadrangular,with margins unequal, deeply excavated, undulate and apices slightly raised into a not very robust process. B. Malleus (Brightwell) H. Van Heurck. (Tr-ceratium Malleus Brightw. ; Q.J. M.S., 1858, vi., p. 154 : H.V.H. At]., pi. 114, f. 1*). Characteristics of genus. Length of valves from one angle to another, 10 c.dm. Marine. — Very rare? Scheldt at Antwerp (Belleroche !) Eastern and Western Scheldt (H.V.H.) England, stomachs of Noctilucce (Brightwell, Kitton). Thames. This species encloses a greenish endochrome ; the valves appear quite smooth ; all kinds of illumination have failed to discover any detail whatsoever. This form is closely allied to Eucampia. I ventured to form this as the type of a new genus which I dedicated to the memory of my former excellent friend the late Professor John Belleroche, an enthusiastic diatomphile, who found the only recorded Belgian specimen which has been in my possession for a long time. The species therefore appeared to be very rare up to June, 1893, when I found specimens which had suddenly developed in a gathering from the Thames. Some weeks afterwards I found some rather numerous examples in one of my pelagic gatherings from near Hansweert LITHODESMIUM. 465 (Western Scheldt) ; then in the August of the same year, I obtained a very abundant pelagic gathering in the Eastern Scheldt, between Ouwerkerk and the red buoy of Sandcreek (Holland). This species, therefore, does not appear to be excessively rare, but entirely pelagic, and found only at certain periods of the year. GENUS 131.— LITHODESMIUM EHR, 1840. go8$* a. h. Fig. 196. — Lithodesmium undulatum, a. Valve view. b. Girdle view. Valve triangular, with angles inflated, raised and terminated by a robust awn. Frustules very slightly silicious, united into a long filament, and connected with one another by a cellular membrane. L. undulatum Ehr. (Kreideth, p. 75, No. 49, pi. 4, f. 13; H.V.H. Atl., pi. 116, f. 8-1 1* ; Type No. 506), plate 19, fig. 627. Valve triangular, with undulated margins, apices raised and ending in a robust awn, simple or bifurcated , centre elevated and furnished with a strong spine ; stria; delicate (about 10 to 14 in 1 c.d.m. at the margin of the valve), radiant, finely punctate. Length from one apex of the valve to another, 4 to 6 c.d.m. Girdle face quadrangular, connecting zone with excessively delicate longitudinal striae, about 20 in 1 c.d.m, interrupted by transverse hyaline lines. Frustules united into a filament and closely connected to one another by a membrane marked with coarse puncta in quincunx, and forming 10 to 12 longitudinal striae in 1 c.d.m. Marine. — Not rare. Blankenberghe in the 2nd Basin. GG 466 BIDUULPHIA. IV. Eubiddulphie/E. — Valves having at the apices pro- cesses more or less obtuse, and of greater or less length. GENUS 132.— BIDDULPHIA GRAY, 1831. Frustules free or united into filaments either continuous or in zig-zag. Valves elliptic, suborbicular, triangular, quadrangular, etc. ; margins even or undulated, usually more or less inflated at the median portion, rarely depressed, showing elevated, obtuse processes at apices, and having also sometimes hornlike processes. Girdle face more or less quadrangular, showing distinctly processes which are not so visible in the valve face. Connective zone very obvious. The genus Biddulphia is of vast proportions ; it includes some hundreds of species and the genus requires a serious monograph written by a thoroughly competent specialist who shall have devoted a very considerable time to its examination and study. Many of the forms belonging to the genus Biddulphia have been arranged in different genera. Genera have even been established, founded simply on the number of angles of the valve, such are Triceratium, Amphitetras, Amphipaitas, Polyceratium ; forms which are found at the same time, and both rhomboidal and angular in form, for example, Biddulphia rhombus (Ehr.) W. Sm., and its forma trigona Cleve {Triceratium slriolatum Ehr.) show that these groups are not admissible. Although, according to the general plan of this work, we are only concerned with the species inhabiting the shores of the North Sea, I shall, nevertheless, give a figure of the type- form of each Genus group which has been established by authors in the genus Biddulphia as I understand it. These groups are as follows : — Group. — Biddulphia (fig. 197, Biddulphia pulchella Gray). „ Odontella (fig. 198, B. {Triceratium) consimile Gr.). ,, Odontella Lampriscus (fig. 199, B. [Triceratium) Shadboltianum Grev.). ,, Zygoceros Ehr. (fig. 200, B. (Zygoceros) circinnus Bail.). ,, Denticella Ehr. (fig. 201, B. (Denticella) granulata Roper). ,, Cerataulus Ehr. (fig. 202, B. {Cerataulus) Smithii Ralfs). ,, Pseudo-stictodiscus (fig. 203, B. {Pseudo-stict.) Eulensteinii Grun.) Triceratium (fig. 204, B. { Triceratium) Favus {Ehr.) H. V.H.). ,, Amphitetras (fig. 205, B. {Amphitetras) antediluviana {Ehr.) H. V.H. ). ,, Amphipentas (fig. 206, B. {Amphipentas) punctata Brightw. RIDDULPHIA. 467 Fig. 197. — Bindulphia pulchella. a. Valve view. />. Girdle view, (Wi 3oo Fig. 198. — B. (Triceratium J con si mi h Fig. igg.—B. ( Triceratium J ShadbolUanum. a. Valve view. b. Girdle view. Fig. 200, — B. (Zygoteros) concinnus. a- b. Fig. 201.— B. (Deniicella) gramdata. a. Girdle view. b. Valve view. 468 BIDDULPHIA. a. t. Fig. 202. — B. ( Ceraiaulus ) Smithii. a. Valve view. b. Girdle view. Fig. 203. — B. ( ' Pseudo-stictodiscus) Eulcnstcinii. b. c. a. Girdle view. Fig. 204.— Z?. (Tricerdtium) Favus. b. Portion of valve with puncta x 1000. c. Valve view. P.IDDULPHIA. 469 Fig. 205— B. (Amphitetras) an tediluviana. Fig. 206. — B. ( ' Ampliipentas) punctata. Under the name of Capsula, Prof. Brun (Le Diat., ii., 1896, p. 235), has separated from Triceratium certain exotic forms having an internal valve with a triangular space curiously fashioned so as to recall the structure of the Entogonia. In this genus Mr. Brun includes two new species, C. Barboi J. Br. and C. biformis J. Br., both from " Colonial " as well as some old forms T. denticulatutn Grev., etc. Lastly, Mr. H. Peragallo has doubtfully suggested the genus Ceratanlina (in Monog. Rhizosolenia) which is differentiated from Ccraiauhts by the relatively great length of the sutural zone, and by its uninterrupted annulation. He includes in it the single form C. Bergonii, found in a pelagic state at Trouville and in the Mediterranean. We shall proceed to the examination of the forms from our district. 470 BIDDULPHIA. ANALYSIS OF SPECIES. f Valves furnished with costae B. pulchella. o o c ■s ■a 'S 3 > > o re > Valve divided into several compartments by very deep constrictions. f All the compartments equally elevated and level with the processes, which are very obtuse . . . B. Regina. I Median more processes apices . compartment considerably elevated than the others ; slender, with inflated B. Tuomeyi. Valves (viewed in girdle face) divided by terminal and median elevations into three portions, almost equal . B. aurita. a o c o u re > a « S .2 e~$ .2 v Si re cue ■o S lj aj -5 .i"S •c o "■> fa Valve furnished with two long awl- shaped spines ; median portion flat or rounded. 2 >.. i/) C a ■o B re o O ~ « j='5 -i re o Valves with cellular structure. Valves punctate, not cellular. I Valve imperfectly silicious ; not furnished with small spines . . B. Valve very silicious, bear- ing numerous small spines B. Several spines placed between the pro- cesses, which are abruptly diminuale towards the apex. Valves broadly lanceolate and inflated at the apices, or trigonal I Spines alterna- ting, with robust pro- cesses, which are not abruptly diminu- ate ; valves not lanceo- late. Valves suborbicular, with cellular girdle . B B. Baileyi. granulata. Rhombus. Smithii. o r re > Spines obscure, placed near the centre of the valve . Spines conspicuous, submarginal, very robust, with api- ces often flattened or bifurcated I B. lsevis. B. turgida. Valves triangular, with cells arranged in straight lines . . . B. Favus. Valves quadrangular, with cells ar- ranged in concentric rows . . B. antediluviana. Valves furnished with vein-like lines, which traverse the valve irregularly and separate the angles from the median portion . . . B. alternans. Valves without vein-like lines, with medium-sized puncta in the median portion, and very fine puncta at the angles . . . B. sculpta. I. — Valves furnished with costce. B. pulchella Gray (Arrang. of Brit. Plants, i., p. 294 Arl, pi. 97, f. 1-3* ; Type No. 487), plate 20, fig. 630. H.V.H. BIDDULPHIA. 471 Valve elliptic, with undulate margins, undulations 3 to 7, each of which arise at one of the costae. Valve with cellular structure, cells arranged in concentric rows round the centre of the valve, becoming gradually smaller as they approach the centre, where there are 2 to 3 short horns generally awl- shaped, sometimes capitate ; processes punctate, puncta becoming gradually finer towards the apex. Girdle face subquadrangular, showing at the apices undulations on a level with the valve, each of which corresponds with one of the costae ; connecting zone with small cells arranged in straight lines (about 5 to 6 in 1 c.d.m.), interrupted by some irregular hyaline lines. Length of valve, 5 to 17 c.d.m. Breadth, 6 to 9 c.d.m. at the median portion. Marine. — Found only once in Belgium in the washing of mussels, but it will probably be found more abundantly, as it exists on all the coasts of the North Sea. England (Ralfs, Griffiths, W. Sm., Bleakley). Ireland (O'Meara). Scotland. II. — Valves without costcz. a. Valves furnished with processes in the form of spines. B. Regina, W. Sm. (S.B.D., ii., p. 50, Pi. 46, f. 323; H.v.H. Atl.,pl. 98, f. 1*), plate 34, fig. 894. Valves lanceolate, with undulate margins, showing three unequal compart- ments between the processes. Girdle face with deep constrictions, which divide the valve into three portions, mammiloid, hemispherical, with coarse puncta arranged in regular lines, intermixed with small short spines. Processes short, obtuse, mammiloid, with puncta becoming gradually finer towards the apices. Connecting membrane with medium-sized scattered puncta. Breadth of valve, 8 to 15 c.d.m. Marine.— Isle of Skye (W. Sm.). Guernsey (Wallich !). B. Tuomeyi Bail. (Am.j.s., 1843, p. 138, f. 3-4; H.v.H. Atl., pl. 98, f. 2-3*), plate 34, figs. 895, 896. This species differs essentially from the preceding, first, by the median compartment being considerably more elevated than the two lateral, and surmounted by 2 to 3 long spines, and next by the processes which are elongated, narrow, refiexed and inflated at the apices. Marine. — This form, so far as I know, has never yet been found on our shores. I only mention it in consequence of some authors having considered that the preceding species is only a variety of B. Tuomeyi. The examination of numerous specimens does not enable me to agree with this opinion. B. aurita (Lyng.) Breb. (Consid. sur les Diat., 1838, p. 12; H.V.H. Atl., pl. 98, f. 4-9* ; Type No. 488), plate 20, fig. 631 472 BIDDULPHIA. Valve elliptic, lanceolate, with apices often diminuate, furnished at the centre with three rather long awl-shaped spines, with coarse puncta (about 10 to 12 in i c.d.m.) arranged in radiating lines, about 10 to 12 in 1 c.d.m. Girdle face showing at its apices the three spines and the three elevations : the median of considerably less height than the terminal, the latter abruptly attenuate at the apex, punctate, with puncta becoming gradually finer. Con- necting zone with puncta of almost the same size as those of the valves, and arranged in longitudinal lines. Frustules forming very long chains. Length of valve, 3 to 8 c.d.m. Marine. — Rather frequent. Blankenberghe, Antwerp (Scheldt), England (Kitton, Stolt., Norman, Comber, Tenner, W. Sm., Roper, Okeden), Scotland (Hennedy, Greville), Ireland (W. Sm., O'Meara), South Wales (Baxter Coll., No. 2815, 2816), North Wales (Shadbolt), and on all the Coasts of the North Sea. var. minima Grun. (H.V.H. Atl., pi. 98, f. 10*), plate 20, fig. 632. Smaller, about 1*25 c.d.m.; puncta fine, about 14 or 15 striae in 1 c.d.m. Marine. — Blankenberghe. var. miniscula Grun., plate 20, fig. 633. Very small; valve with apices longly rostrate diminuate. Marine. — Blankenberghe. B. Rhombus (Ehr.) W. Sm. (S.B.D., ii., p. 49, pi. 45, f. 320; pi. 61, f. 320; H.V.H. Atl., pi. 99, f. 1 and 3* ; Type No. 489), plate 20, fig- 634- Valve rhomboidal elliptic, with apices abruptly rounded, diminuate, furnished with short, awl-shaped submarginal spines of variable number ; striation confused at the centre of the valve, radiant on the remainder, but convergent on the portion corresponding to the apices ; stria? at the centre of the valve, about 9 in 1 c.d.m., formed of coarse puncta slightly arranged in quincunx. Girdle face with the middle valve portion rounded, slightly elevated, processes entirely punctate, with ends gently truncate capitate. Connecting membrane regularly punctate in quincunx, with puncta formed of longitudinal striae, 12 to 14 in 1 c.d.m. Length of valve, 5 to 18 c.d.m. Marine. —Rarer than the preceding. Blankenberghe, Antwerp (Scheldt), England (W. Sm., Bridgman, Roper, Okeden, Kitton, Stolt., Norman, Comber), Ireland (O'Meara). On all the Coasts of the North Sea. var. tngona Cleve. (Triceratium striolatnm (Ehr.) Roper ; H.V.H. Atl., pi. 99, f. 2* ; Type No. 490), plate 20, fig. 635. Differs from the type-form by the triangular shape of the valves, and by its three processes. Marine.— Blankenberghe, Antwerp (Scheldt). Surface of the Dee (Stolt.), Hull (Norman). Thames at Southend (Baxter Coll. No. 2577). BIDDULPHIA. 473 B. Baileyii W. Sm. (S.B.D., ii., p. 50, pi. 62, f. 322 ; Zygoceros mobilicnsis Bail. ; H.V.H. Atl., pi. 10 1, f. 4-6*), plate 20, fig. 636. A delicate, very imperfectly silicious diatom. Valve broadly lanceolate, bearing two spines alternating with the terminal processes, and situated at the lower and upper third near the longitudinal axis of the valve ; puncta in quincunx very delicate, about 12 to 14 striae in 1 c.d.m. Girdle face showing the valve portion with centre flat or concave, the conical terminal processes completely punctate, with truncate, somewhat capitate, ends, they and the spines very long, somewhat bifurcated at the apex, each being borne on a small elevation of the valve. Connecting membrane with puncta in quincunx, excessively delicate, about 18 striae in 1 c.d.m. Length of valve, 7 to 16 c.d.m. Marine.— Blankenberghe (H.V.H.), England (W. Sm., Williamson, Kitton, Stolt., Norman, Comber), Ireland (O'Meara), B. granulata Roper (T.M.S., 1859, vii., p. 13, pi. 1, f. io-u, pi. ii., f. 12 ; H.V.H. All., pi. 99, f. 7 and 8, and pi. 101, f. 4*. In the latter figure the general outline is very exact, but in the fair copy of the drawing the small spines on the valve have been accidentally omitted; Type No. 492), plate 20, fig. 637. Valve ellipticdanceolate, bearing two very long spines alternate with the terminal processes, approximate to them and to the longitudinal axis of the valve ; striated in quincunx (about 13 or 14 in i c.d.m.), and bearing numerous small awl-shaped spines, about 4 in 1 c.d.m., placed in irregular lines. Girdle face quadrangular, showing the valve portion with the centre fiat or concave, the processes inflated, then abruptly attenuate on the external side, punctate up to the apex, which is somewhat rounded, and the spines very long, often flexed at an obtuse angle near their middle. Connecting zone with puncta in quincunx, with 14 stria? in 1 c.d.m. Length of valve, 5 to 8 c.d.m. (in the specimens observed). Marine. — Very rare. Antwerp (Scheldt), Blankenberghe, England (Coll. W. Arnott !, Comber, Stolt., Norman). B. turgida W. Sm. (S.B.D., ii., p. 50, pi. 62, f. 38; Cerataulus turgida Ehr.; H.V.H. Atl., pi. 104, f. 1 and 2* ; Type No. 495), plate 21, fig. 638. Valve varying from a round to a longly elliptic form ; sometimes furnished near the margin with a circlet of very short spines, bearing diagonally two broad truncate processes and two stout spines ; striae undulate, 9 in 1 c.d.m., 474 BIDDULPHIA. formed of rather coarse beads and intermixed with innumerable abbreviated spines. Girdle face subquadrangular, slightly twisted, at the median portion showing terminal processes very broad, truncate, completely punctate, and the two spines very robust, with apices often bifurcated. Connecting zone with striae formed of puncta, placed in quincunx; somewhat undulated, delicate, about 12 in i c.d.m. Length of valve, 7 to 13 c.d.m. Marine. — Very rare. Antwerp (Scheldt), Blankenberghe, England (Okeden, Kitton, Stolt., Norman. Comber), Ireland (O'Meara). Found on all the Coasts of the North Sea. B. lsevis Ehr. (Ber., 1843, P- 122> Odontella polymorpha Kiltz. ; H.V.H. Atl., pi. 104, f. 3 and 4*; Type No. 496), plate 20, fig. 639. Valve suborbicular or broadly elliptic, bearing near the longitudinal axis two spines opposite, short, obscure, with punctate, radiate striae, somewhat undulate and as it engine-turned, delicate, about 15 or 16 in 1 c.d.m., inter- mixed with abbreviated scattered spines. Girdle face with terminal processes very short, obtuse, truncate, punctate up to the margin. Connecting zone with delicate striae (about 16 in 1 c.d.m.), punctate in quincunx. Length of valve, 5 to 12 c.d.m. Marine. — Antwerp (Scheldt), England (W. Arnott). forma minor. (H.V.H. Atl., pi. 105, f. 4*), plate 20, fig. 640. Smaller, terminal processes scarcely marked. B. Smithii (Ralfs) H. Van. Heurck. (Bidduiphia radiata Roper ; Ceraiauhts Smithii Ralfs ; Enpodiscus radialus W. Sm., nee Bailey ; H.V.H. Atl., pi. 105, f. 1 and 2* ; Type No. 497), plate 21, fig. 641. Valve almost orbicular, sometimes bearing numerous spines, with hexagonal cells, furnished with two marginal processes and two awl- shaped spines rather short, submarginal, forming an angle of 900 with the terminal processes. Girdle face showing in the valve portion the two long terminal processes which are conical, truncate, and entirely punctate, and the two awl-shaped spines not very robust. Connecting zone finely punctate, with puncta in regular lines, about 10 in 1 c.d.m. Frustules free. Length of valve, 4 to 12 c.d.m. Marine.— Very rare. Blankenberghe (2nd Basin), 1878 ; Antwerp (Scheldt), England (W. Sm., Stolt., Norman, W. Arnott !), the Thames (Baxter Coll., No. 2579, 3450). BIDDULPHIA. 475 b. Valves without spines. * VALVES WITH CELLULAR STRUCTURE. B. antediluviana (Ehr.) H. Van Heurck. (Amphitetras Eh*-. ; H. V.H. Atl, pi. 109, f. 4 and 5* ; Type No. 501), plate 21, fig. 642. Valve quadrangular, with margins straight or concave, centre depressed, four robust processes, finely punctate ; structure cellular, cells in concentric circles, allowing the puncta of the inferior layer of the valve to be slightly seen in the transparent portion. Girdle face quadrangular, with valves constricted near the sutural zone. Connecting membrane with coarse puncta forming irregular longitudinal lines, about 4 to 5 in 1 c.d.m., interrupted by transverse hyaline spaces. Frustules forming bands, generally in zig-zag. Length of valve, 2*5 to 14 c.d.m. (in the latter measurement the concavity of the valve has not been substracted ; from one excavation to another, the length would not be more than n c.d.m.). Fossil. — Potter's clay at Ostend ( Oeby). Found not only on all the Coasts of the North Sea, but also on all the Coasts of Europe, America, etc. England (W. Sm., Okeden, Ralfs, Griffiths, Kitton), Orkney Islands (Baxter Coll., No. 3111, 3112), Ireland (O'Meam), Guernsey (Baxter Coll., No. 3114). var. pentagona. (Amphipentas Ehr.). Valve with five angles. Not yet found in Belgium. England (Hodgson), Scotland (Hennedy). B. Favus (Ehr.) H. Van Heurck. {Tricer atium Favus Ehr.; H.V.H. Atl., pi. 107, f. 1-4* ; Type No. 500), plate 21, fig. 643. Valve triangular, with centre convex ; three terminal processes robust, elevated, finely punctate up to the ends ; sides straight or somewhat convex. Structure with coarse hexagonal cells allowing the fine puncta of the inferior surface of the valve to be seen. Partitions of the cells embellished with small spines. Length of girdle face much greater than the breadth ; con- necting zone delicately striate lengthways (about 16 striae in 1 c.d.m.), with puncta in quincunx. Length at the margin of a valve of medium size, 9 to 15 c.d.m. Marine. — Rather common. Blankenberghe, Ostend, Antwerp (Scheldt), and found almost everywhere. England (Shadbolt, Hodgson, Kitton, Stolt. , Norman, Comber). *• VALVES PUNCTATE, NOT CELLULAR. B. alternans (Bail.) H. Van Heurck. (Trkeratium aiter- nans Bailey ; Mic. Observ., South Carol.; H.V.H. Atl., pi. 113, f. 4, 5 and 7*; Type No. 505), plate 21, fig. 644. 476 ENTOGONIA. Valve triangular, with straight margins, three terminal processes slightly elevated, separated hy nerve-like lines from the median portion and having in addition, here and there, some nerve-like lines which extend across the valve entirely or partially. Structure cellular ; cells irregular, gradually diminishing towards the margins and the processes, which are punctate up to the end. Girdle face much broader than the length, showing 3 to 4 costoe, with undulated margins, cells small, in longitudinal rows, about 12 rows in 1 c.d.m. Connecting zone very narrow. Frustules usually united in twos. Length of valve, 4*5 to 5 c.d.m. Marine. — Rather frequent. Blankenberghe, Antwerp (Scheldt). England (W. Sm., Capron, Kitton, Norman, W. Arn. !). Courseules, France (Br6b.). Holland (Suringar). Ireland (O'Mearaj. B. sculpta (Shadb.)H. Van Heurck. {Trkeratium scuiptum Shadb., T.M.S., 1854, ii., pi. 1, f. 4; H.V.H. Atl., pi. 109, f. 7 and 8* ; Type No. 502), plate 21, fig. 645. Valve triangular, with straight sides, three terminal processes slightly elevated ; structure cellular, cells irregular, of almost equal size throughout the valve ; processes finely punctate. Girdle face longer than the breadth ; valve portion undulated, with cells arranged in longitudinal rows ; 6 lines in 1 c.d.m. Connecting zone rather broad, having 7 or 8 longitudinal rows of coarse dots in 1 c.d.m. Length of the valve margins, about 4 c.d.m. Marine. — Rare. Antwerp (Scheldt) ; Potter's clay from Ostend (Deby) ; Sweden (Lagerstedt). I think this form has escaped collectors, and will be found elsewhere. GENUS 133.— ENTOGONIA GREV, 1863. Valves angular, usually with three angles' leaving at the centre a smooth portion, with the marginal portion divided into compart- ments by false costae, which correspond with internal septa ; angles of the valve more or less elevated into processes. 'S ' ^inopinata The genus Entogonia includes about 20 species, all fossil, and found especially in the deposits from Barbadoes and Jeremie (Hayti). I give in the text (fig. 207) E. inopinata Grev., from the Cambridge Estate (Barbadoes). The genus Habergia, according to Mr. Bergon, should be suppressed ; the genus being in his opinion founded only on a biangular form of E. Davy a na Grev. PORPEIA. 477 GENUS 134.— PORPEIA BAILEY, 1861. a. Valves oblong, with strong distant puncta, inflated at the median portion, constricted at the apices, which are inflated, rounded, obtuse, capitate, finely punctate. Girdle face compressed, showing flexed internal septa. The genus Porpeia includes four species, all fossil, except P. quadriceps Bail, which has been found in a living state in the Gulf stream and at the Galapagos Islands. I give in the text (fig. 208) ig, 2oB.-Porpeiaquadrata. P- quadrata from Sta. Monica. It is represented in a with, and in b without, the sutural membrane which covers it. GENUS 135.— TABULINA BRUN, 1889. b. a. \,; ;: ■•••.".;■.• V.°. ^»t?..«' ' 'c,*°o/ - '"'.'.••Y.'-y''-'- fl Valve flattened, tabular, broadly elliptic, furnished with hyaline channels, radiant and transverse ; four protuber- ances rounded and striated. Girdle face rectilinear. I give in the text (fig. 209) from one of my photographs a drawing; of Talndina Testudo Bum., the unique species of the genera. It is a very rare form which was discovered by Pro- fessor Brun. in the Limestone of Yedo (Japan). Fig. 209. — Tabulina Testudo. 478 ODONTOTROPIS. GENUS 136.— ODONTOTROPIS GRUN, 1884. Valve biddulphoid, furnished with two long aculeate horns, con- nected by a pectinate, dentate or smooth keel. This genus includes about half a dozen curious forms, two of which, O. carinata Grun. and O. cristata, are found in the Cemenstein of Mors. Figure 210 in the text represents O. crisiata. It has unfortunately been made from an imperfect specimen. It should appear as if the right side was similar to the left, and the dentated comb should extend throughout the surface, which separates the two horns. Fig. 210. — Odontropis cristata. GENUS 137— KERATOPHORA PANT., 1889. Valve biddulphoid, broadly elliptic, with coarse puncta, furnished with two very long robust, tortuous horns, often bifurcated. Fig. 211. — Keratophora robusta. a. Valve view. & Girdle view. KITTONIA 479 The genus includes two species, K. nitida P. and K. robusta P. (fig. 211), represented in the text, after one of my photographs, taken from a specimen forwarded by Dr. Pantocsek. The two species are found in a fossil state at Kusnetzk (Russia). GENUS 138— KITTONIA GROVE & STURT, 1887. Fig. 212. — Kittonia elaborata. Valve biddulphoid, elliptic, furnished with two processes, the apex of each being enlarged and widened into a cup. This genus comprises three species, one of which (K. gigantea Grev.) is ound in the deposit of Cambridge Estate, Barbadoes, while the other two have been found in the deposit of Oamaru, New Zealand. I give in the text (fig. 212), one of them, the most beautiful, K. elaborata, Grove and Sturt, drawn from one of my photographs. 480 HUTTONIA. 1 GENUS 139. HUTTONIA, GROVE & STURT, 1887. Valve showing two alternate elevations or ocelli. This genus appears intermediate between the Biddulphiece and the Eupodiscice, and requires further examination. The figure in the text is of H. alternaus, Gr. and St., from one of my photographs. This diatom is found in the deposit of Oamaru. Fig. 213. — Huttonia alternans. GENUS 140.— GROVEA AD. SCHMIDT, 1890. Valve discoid, showing 7 to 8 mammiform-ocelliform marginal elevations, between each of which is an obtuse rounded marginal projection, placed lower than the pre- ceding, and apparently turned in an opposite direction. Centre occupied by a broad umbilicus surrounded by a clear space communicating by clear radiant spaces with Fig. 214. -Graven fedaiis. the margin of the valve, intermediate portions very delicately punctate and bearing here and there coarse puncta. The figure in the text is Gr. pedalis (Gr. and St.) Ad. Schm., having its origin in the Oamaru deposit, and which Messrs. Grove and Sturt described under the name of Biddulphia pedalis, a name also adopted by Grunow. I, however, find this diatom differs sufficiently to justify the name given it by Dr. Ad. Schmidt. eupodisce.*:. 481 Tribe XXII. — Eupodisce/E. TABLE OF GENERA. Valves with mammi- form elevated ocelli, surrounded by a hyaline zone, whence emeige solid 01 granular rays, usually arranged like feathers ot a quill pen. Valves round or elliptic. f I Generally 2, rarely 1 or 3 ocelli A single ocellus, eccentric Auliscus. Monopsis. Valve subquadrangular, an^le having an ocellus at each Glyphodiscus. Valves round or elliptic, cellular or granular, with median hyaline space absent or very small ; striation usually radiant ; two to nine processes surrounded hy a hyaline zone o ,0 re o a to > Pseudo-auliscus. Valves with striation radiant, interrupted at the median por- tion by a linear hyaline space .... Fenestrella. ■3 ! > o .0 re o a re > f Valves with connecting project costne, moniliform rays or well marked sulci the processes or tubercles, which usually much Aulacodiscus. f Valves circular or oval, with ocelli placed in • com- partments . . . . . O JO re ~ -I re > Valve with cellular structure. Craspedoporus. ' Valves with very fine puncta, indistinctly radiant, showing near the centre a circle of coarser dots and at the margin a corona of dots and a small elongated process Micropodiscus. 0) > o .0 re * i o o a re > Valves circular, with radiating rows of small puncta and coarse marginal tubercles . Perithyra. Tubercles marginal, rather small, all similar, forming a complete circle ; valves granular, with granules radiating, circular or oval or angular o ■a re O c « > Cestodiscus. I o .n re o c > I Tubercles unequal, 2-3 large, placed at an equal distance between the smaller . . . Isodiscus. > o .a re re > Valves with ocelli small, nu- merous, each of them being separated by a small process from the next Ocelli, tubercles or pro- cesses usually very Rattrayella. > o & re if) re o re > I large, not numerous and usually submarginal ; valve cellular or granu- lar ; granules rarely radiating or small Valves with two large elevations, of very slight height .united or covered with radiating puncta ; puncta very fine, ar- ranged in radiating or anastomozing rows Eupodiscus. Pseudo-cerataulus. Ocelli very large or very prominent, few in number and usually submarginal, cells rarely radiating . . Eupodiscus. I J Ocellus single, submarginal ; valve showing according to the focus either hexagonal cells or fine puncta . Roperia. Ocelli two, placed on the same side of the valve in a large elongated hyaline depression . . . Bergonia. H H 4g2 AULISCUS. GENUS 1M.-AULISCUS (EHR.) Bailey emend., 1854. Frustule cylindrical or discoid. Valve with rays either plumose plaits or with granules arranged round two mastoid processes (or ocelli), rarely obscure, sometimes with a sub- quadrate central portion a. b. Fig. 215. — Auliscus sculptus. a. Girdle view. />. Valve view. or with a radiant cellulation interrupted by a linear series terminating in the ocelli. The beautiful genus Auliscus comprises about 100 species, among which A. sculptus figured in the text (fig. 215) is the only form hitherto found on our coasts, but to this should be added var. coelata (A. ccelatus Bail.), which certainly belong to us, as I have in my possession specimens from different localities. Lastly, I have to record A. punctatus Bail, which I discovered on the mud of the Scheldt at Antwerp, but until further specimens have been found, I shall consider this one as having been accidentally brought by a vessel. The specimen found belonged to the var. Carpentaria. ANALYSIS OF FORMS. f Valve divided into four f The plicee of each compartment robust and similar A. sculptus. j compartments by two | series of plicae placed -J The plicee of compartments with ocelli robust, ; at a right angle. entire ; those of the intermediate compartments ">, ^ delicate, and resolving into fine granules . var. coelata. delicate, and resolving into fine granules Valve without any distinct compartments, plicae very delicate, regularly k. radiating and bearing coarse distant granules . A. punctatus. A, SCulptUS (W. Sm.) Ralfs. (in Pritch. Inf., p. 845, pi. 4, f. 3; Eupodiscus sculptus IV. Sm.; H.V.H. Atl., pi. 117, f. 1 & 2*; Type No. 507), plate 21, fig. 646. Valve suborbicular, marked at the margin with radiating plicae and leaving in the centre a quadrilobal space. In this space arise four other series of plicae, of which the two bearing the ocelli radiate from them towards the centre of the valve, while the two others radiate from the centre towards the margin of the valve. Length of the valve, 4 to 9*5 c.d.m. Marine. — Antwerp (Scheldt). Blankenberghe (H.V.H. ), Bed of a dam (Potter's clay (fossil) at Bruges (Deby), Holland (H.V.H. , Suringar), England (W. Sm. ! Gregory! W. Arnott, Kitton, Norman, etc.), Ireland (O'Meara.). var. coelata (A. ccelatus Bail.). See the description in the analytica table above. Antwerp (Scheldt), Blankenberghe (H.V.H.) PSEUDO-AULISCUS. 433 AulisCUS punctatUS Bail. (Smith's Contr., 1853, p. 5, f. 9; Ad. Sch. Atl., pi. 67, f. 7-8 and various plates) is a tropical species which is only included in our Table of Forms in consequence of a slight similarity of certain of its forms with A. ccelatus Bail. GENUS 142.— PSEUDO-AULISCUS LEUD-FORT., 1879. Valves round or elliptic, cellular or granular, with median hyaline space absent or very small ; striation usually radiate, 2 to 9 processes surrounded by a hyaline zone. This genus includes about 25 species, all exotic and for the most part fossil, found in Oamaru, Barbadoes, Hungary, etc. The figure in the text (fig. 216) is Ps. ambigtius (Grev.) Rat/ray, from the Cambridge Estate, Barbadoes. Fig. 216. — Ps. Auliscus ambiguus. GENUS 143.— PSEUDO-CERATAULUS PANT., 1889. Fig. 217. — Ps.-Cerataulus Kinkeri. 484 MONOPSIS. Valves elliptic or rounded, furnished with two slight elevations, very large, plain, or covered with radiating puncta. Valve with very fine puncta, arranged in radiating rows, anastomosing. Central puncta sometimes robust, scattered. The genus Pseudo-Cerataulus comprehends three fossil forms from Hungary. In the text will be found P. Kinkeri Pant. (fig. 217), reproduced from one of my photographs made from a type specimen that Dr. Pantocsek was good enough to forward me. GENUS 144.— MONOPSIS, GROVE & STURT, 1887. Fig. 218. — Monopsis mammosa. \ Valves circular, with centre depressed, margins slightly elevated. A pseudo-ocellus or process, eccentric, round, covered with elongated puncta arranged in radiating rows. Striae very delicate, finely punctate, plumose, arranged in radiating flexed rows, arising from the process. A single example, Monopsis mammoso Gr. and Sturt, having its origin in he Oamaru deposit, and shown in the text (fig. 21S), after my photograph. GLYPHODISCUS. 485 GENUS 145.— GLYPHODISCUS GREV., 1862. Valve irregularly circular, generally subquadrangular, with a pseudo-ocellus at each angle centre umbilicate, more or less smooth, umbilicus surrounded by radiating striae, very delicate, terminating in a fine reticulation. This genus includes three fossil species, all found in the Oamaru deposit. The figure in the text Fig. 219.— 6 lyphodiicus stellatus. represents Glyphodiscus steliatus Grez'., which is found in very different localities (Oamaru, Cape of Good Hope, Sta. Monica, etc.), and is the type-form of the genus. GENUS 146.— FENESTRELLA GREV., 1863. Valve circular, slightly convex, with a border of small semi-circular hyaline areas, and having two ocelli opposite one another, to- wards the inner third ; strise radiant, except between the two ocelli, where they form straight lines, interrupted at the central portion by a transverse hyaline line. This genus was created by Greville for F. Barbadensis Fig. 220. — Fenestrella Barbadensis. Grev. (fig. 2 2o), a heautiful species from the Cambridge Estate, Barbadoes. Professor Brun has added to it two other fossil species from Oamaiu and Yeddo (Japan) respectively. 486 BERGONIA. GENUS 147.— BERGONIA TEMPERE, 1891. Valve almost circular, slightly con- vex,with cellular structure, interrupted by two large hyaline spaces, subreni- form, opposite one another, and inclined to one another at an angle of 40. Each hyaline area encloses at its median and dorsal portions a small oblong ocellus, whence arise two silicious inflations, running in a direction towards the apices of the Fig. 221.— Bergonia Barbadcnsis. hyaline Spaces. This genus only comprises one species, Bergonia Barbadensfs Temp. (fig. 221), from the Barbadoes deposits. My figure is drawn from a photograph which I made from a valve Mr. Tempere was good enough to entrust to me. GENUS 148.— EUPODISCUS EHR, 1844. Fig. 222<5. — Eupodiscus Argus. Girdle view. Fig. 222rt. — Eupodiscus Argus. Valve view. AULACO DISCUS. 487 Valves disciform, with cellular or granular structure, without a median area, furnished with 1 to 4 processes, which are not connected with one another by costae or sulci. Girdle face rather narrow. The genus includes about 15 species, only one of which belongs to our coasts, E. Argus (fig. 222), which Mr. Rattray ranks among the Aulacodiscus. I find the structure much too peculiar to rank in that genus, and I shall therefore preserve it here. A certain number of the Eupodiscus are fossil. They are found in the Barbadoes deposits. Others again are found living, and belong especially to warmer regions than ours. E. ArgUS Ehr. (Kreideth, p. 77, No. 60; H.V.H. Atl., pi. 117, f. 3-6*; Type No. 508), plate 21, fig. 647. Valve orbicular, convex, furnished with 3 to 5 rather robust processes, inflated at the apices; formed of two very different layers; the superior with coarse irregular alveoles with openings from above, the inferior with puncta arranged in radiating rows. Girdle face with convex margins; con- necting zone showing some transverse plica? and longitudinal stria?, punctate, delicate, about iS to 20 in 1 c.d.m. Diameter of valve, 8 to 20 c.d.m. Marine. — Blankenberghe, Ostend, Antwerp (Scheldt), and on all the coasts of the North Sea. England (Shadbolt, Kitton, Stolt., Norman). Ireland (O'Meara). E. commutatus Grev. and E. u/s Grev. are only forms of Coscinodiscus concinnus, a description of which will be found in a later page. GENUS 149.— AULACODISCUS EHR., 1845. Valves generally cir- cular, granular, furnished with processes, variable in number, connected with oneanotherthrough the centre, either by a sulcus or by costal, or by granules arranged in special lines This genus includes a considerable number of forms almost all remarkable for their beauty, as may be seen from figure 223, which represents A. orienta/is Grev., after Ad. Schmidt. > Fig. 223. — - Aulacodiscus orientalis. 488 AULACODISCUS. A large number of the Aulacodiscus are found in fossil deposits, others inhabit tropical seas, where they are sometimes found in immense numbers ; it was in this way that my friend, Mr. Hens, in his Botanical expedition to the Congo, found the sea coasts at Banana covered with a greenish bed of A. Africanus Cott. (A. Kittoni Arnott var.), and was able at once to fill a large vessel with this species, absolutely pure. The first general aspect oiA . zonulatusRattr. is quite different from an ordinary Aulacodiscus, while Dr. Pantocsek has made a special genus of it under the name of Tchestnovia (« g. 224). Mr. A. Rattray has published a good mono- graph of this genus under the title of " A revision of the genus Aulacodiscus Ehr." It will be found in the Journal of the Royal Microscopical Society for Fig. 224. — Aulacodiscus zonulatus. the year tSSS. It is necessary to refer to it in studying this genus CRASPEDOPORUS. 489 GENUS 150.— CRASPEDOPORUS GREV., 1863. Fig. Q.o.^.—Crastedoporus Ralfsianus. Valves circular, with cellular structure, apparently divided into compartments, in consequence of portions of the valve being elevated, each of which portions (5 to 1 1 in number), bears an ocellus or pseudo- pore at a more or less approximate distance from the margin. Central portion of the valve forming a paler-coloured area, with small and less distinct cells. This genus comprises about half a dozen species, all fossil. In the text will be found (fig. 225), after Greville, Cr. Ralfsianus Gr., from the Cambridge Estate, Barbadoes. I have never seen this form, but I think that the contrast between the compartments is much exaggerated. 49° ROPERIA. GENUS 151.— ROPERIA GRUN., in H.V.H. Atl., 1885. Fig. 226. — Roperia tessalata. Valve circular or subcircular, with plane surface, structure cellular, cells punctate, puncta decussate, furnished near the margin with a round hyaline spot or pseudo-ocellus. A single species. R. tessalata (Roper) Grun. (in H.V.H. Atl., pi. 118, f. 6* Eupodiscus tessalatus Roper; QJ.M.S.., 1858, vi., p. 19, pi. 3, f. 1 a-b\ fig. 226 in text. Valve from 6 to 7 c.d.m., having about 6 cells in 1 c.d.m. near the middle of the valve, smaller and more approximate near the margin. Hyaline spot, about "25 c.d.m. in diameter. Marine. — England: Caldy, Pembrokeshire (Roper), Hull (Norman, Gregory, Greville) Finistere (Greville). West Coasts of Africa (" Gazelle " Expedition, Weissrlog). Cape GENUS 152.— ISODISCUS, RATTRAY, 1888. •".v.°v.V.->--v.;v;4-^r.:v:; •>•.!• ;♦.•*.•••:•* Fig. 227. — Isodiscus mirificus. Valves circular, with coarse puncta, furnished at the margin with 2-3 large processes, surrounded by fine radiating puncta, and between them several pseudo-ocelli. This genus only includes two species, both fossil, from Oamaru. I give in the text I. mirificus Raft., after Rattray (fig. 227). RATTRAYELLA. 49 1 GENUS 153.— RATTRAYELLA. DE TONI. 1889. life - - ■ :_-.' . - .* *-?/'Yt&:^ ■'-'■' 4F& mh - . ." '-. s^g. mmm ^%m £S-3a i#s ££: Valves circular, plain in the median portion, then gently convex towards the margin, very finely punctate, with puncta arranged in radiating lines and often covered with a kind of vague network. Margin showing small processes, rounded or elliptic, between each of which is one or two apiculi. This genus only comprises Fig. iT&.—Rattrayella Oatr.arucnsis. a single species. B . Oamciril- ensis (Grun.), De Toni, found in the fossil deposits of Sysran, Simbirsk and Ananino (Russia), as well as in the deposit of Oamaru. The figure in the text (fig. 22S), is drawn from one of my photographs. GENUS 154.— CESTODISCUS GREV.. 1865. Valves disciform, circular, oval, rarely angular, granular, with granules arranged in radiating rows, furnished with round or elongated tubercles, forming a complete circle, near the margin of the valve. Fig. 229. Cestodiscus Pr This genus only comprises a small number o* species, the greater part being fossil. I include in my generic diagnosis Trkeratium cinnamomeum Grev., which should, perhaps, form a special genus. The figure in the text (fig. 229), represents Cestodiscus Proteus Hard- man, after an authentic example of the author. Mr. Rattray classes the Cestodiscus, Perithyra, and Micropodiscus among the Coscinodiscus. 492 PERITHYRA. GENUS 155.— PERITHYRA EHR, 1854. Valves circular, with fine puncta arranged in radiating rows, and with coarse marginal tubercles. This genus, which appears rather doubtful, includes, according to Ehrenberg, two forms, P. denaria Ehr. (fig. 230) and P. quarternaria Ehr., which only differs in having four tubercles. These torms are found in the Ganges. For anything I Fig. 230. Perithyra denaria, know, they have never been seen by anyone but Ehrenberg GENUS 156.— MICROPODISCUS, GRUN., 1883. Fig 231. Micropodiscus Weissflogii. Valve with margin furnished with a circlet of dots (or small awl-shaped spines) and of a small elongated process. Puncta very fine, indistinctly radiant ; a circle of coarser dots near the central portion. A single species. M. Weissflogii Grun. ! (in H.V.H.'s Types, Nos. 11 and 416), fig. 231 in the text. Characteristics of the genus ; the awl-shaped spines of the circlet 10 to 13 in 1 c.d.m. Diameter, "5 to 1*5 c.d.m. Brackish w<~ter — Blankenbei-CThe. Tribe XXIII— Heliopelte/E. TABLE OF GENERA. Valves with triangular or cuneate compartments, equal, alternately- depressed and elevated, usually two layers, one reticulate, the other punctate f Valve very finely punctate, over the whole surface, elevated portions ending in an edge, giving the appearance of spokes of a wheel, each terminated by a large ocellus c o o G V ■Si 5 > c o c o o c. -a 3 •o c D Actinoptychus. Actinodiscus. > O .O 1) > f Umbilical area covered with scattered coarse blurs. Valve with coarse puncta divided into cuneate compartments by the interposition of elevated plicae . . ■ Truania. f Valve with numerous marginal compartments, separated by septiform depressions ; umbilicus rounded, hyaline. Intermediate portion finely punctate, puncta radiating, interrupted at certain distances by blank spaces .... Anthodiscus. f Valve with unequal compartments ; elevated com- partments very narrow, ending in a process ; depressed compartments broad, reticulated, triangular, interrupted at the base by a short elevation, elongated into the umbilical hyaline portion ..... Actinodyction. f Margin showing numerous elevations (they themselves being subdivided) and separa- ted by deep sulci ; sulci in the form of £ scales at the edge of the margin and extending towards the interior as far as the umbilicus I v > o .a - 1 o c > > o ■a I Lepidodiscus. o G I I Valve similar to the preceding, from which it differs by the whole median portion being occupied by strias, radiant, flame- iike,' very finely punctate, and by the finely granular umbilicus, surrounded by a hyaline circle Wittia. GENUS 157.— ACTINOPTYCHUS EHR, 1838, Char, emend. Fig. 232. — Actinoptychus undulatus , 494 ACTINOPTYCHUS. Fig. 234.— A. (OmphalopeltaJ undulates. Fig; 233. — A. ( ' Debya) undulatus, Fig- "z^S—Actinoptychus Heliopelta. ACTINOPTYCHUS. 495 Fig. 236. A. (Polymyxus) fulchellus. Fig. 237. — A. (Schuettia) annulatus. Valves circular, rarely triangular, with triangular compartments alternately smooth, elevated or depressed, structure usually alveolar and with a central polygonal umbilicus. Alveoli placed on a punctate lamina (which is sometimes the only one present), with or without hyaline spaces and small submarginal spines at the circumference of the valve. Frustule disciform, undulated, divided into compartments, with girdle face narrow. The genus Aciinoptychus is widely extended, embracing more than 100 species, the greater number of which are fossil, and remarkable for their beauty or elegance. A typical valve of A. undulatus Ralfs. is represented in figure 232. Several genera have been created at the expense of the genus Actinopty- chus, amongst which we may mention : — Debya Pant., 1886 (non Rattray) (fig. 233), drawn from one of my photographs, which is founded on the interior valves of A. undulatus Ralfs. I have frequently found these valves in the mud of the Scheldt and the sediment of the North Sea, and I have in my possession specimens where this internal valve can be clearly seen through the normal valve. Gyroptychus contabulatus. Ad. Schm., described hereafter among the Asterola/nprea-, is probably only the interior lamina of an Aciinoptychus. Omphalopelta Ehr., 1844, comprehends the Aciinoptychus with a spine or process in alternate compartments. A. undulatus is very often found in this state. 496 ACTINOPTYCHUS. Symbolophora Ehr., 1844 (non Grunow), with valves having an angular centre. Heliopelta Ehr., 1854, the type-form of which is A. Heliopelta Grunow (fig. 235), characterised by its numerous spines or teeth on the margin. Halionyx Ehr., 1854, includes such of the Actinoptychus as have the central portion rounded. Polymyxus Bail, 1885. are the Actinoptychus without a cellular layer, and with strongly undulated valves. In the text (fig. 236), will be found Polymyxus pulchellus, Gr., which deviates somewhat from the normal type- form (P. toronalis L. IV. Bail.). A figure of the latter will be found in H.V.H. Atl., pi. 123, f. 4, which is identical with an Actinoptychus, where the cellular layer is absent. Schuettia De Toni, 1894, are Actinoptychus with triangular valves ; the figure in the text (fig. 237), represents A. annulatus ( Wall.) Grun., which is the type-form of this new genus. This form is met with at Java and in the China Sea. If a new genus is to be constituted for triangular forms, the name given by Dr. De Toni is untenable, but it should be called Cymatogonia, which was proposed by Mr. Grunow in 1883, in the "Botanisches Centralblatt," No. 36 (vol. xv., No. ro). There are only two Actinoptychus to be found in our regions. ANALYSIS OF SPECIES. "Valve having usually six compartments, with large hexagonal central umbilicus . . . . . . .A. undulatus. - Valve having from 12 to 20 compartments, with umbilicus dentate, teeth ,. truncate ... . . A. splendens. A. undulatus Ehr. (Act. Mternarius Ehr., Mik., pi. 18, f. 20; H.V.H. Atl., pi. 122, f. 1 and 3, and pi. 22 bis, f. 14* ; Type N0.514), plate 22, fig. 648. Valve usually with six compartments, a large umbilicus, polygonal," central, smooth, and usually furnished with a small process, placed on the submarginal median portion of each alternate compartment. Alveolate lamina, with large hexagonal alveoli; punctate lamina, with puncta fine, in quincunx; about 16 striae in 1 c.d.m. Diameter of valve, about 4 to 12 c.d.m. Marine. — Common. Blankenberghe, Ostend, Antwerp (Scheldt.), and in all mud deposits of the North Sea. England (W, Sm., Hodgson, Kilton, Stolt,, Norman, Comber), London clay (Baxter Coll., No. 2309), Northumberland (Baxter Coll., No. 2829), Devonshire (Baxter Coll., No. 2841), TRUANIA. 497 A. splendens (Shad.) Ralfs. (in Pritch., p. 840; Actinophenia splendens Shad., T.M.S., 1854, ii., p. 16 ; H.V.H. Atl., pi. 119, f. 1, 2, and 4* ; Type No. 511), plate 22, fig. 649. Valve with 12 to 20 compartments, rising gently from the middle up to the margin, where a costa separates each compartment from the adjoining; furnished with a submarginal band, apparently smooth (in consequence of being placed out of focus) ; costse having a small spine at their marginal apex ; umbilicus dentate, with teeth truncate, each dentlet corresponding with the base portion of a compartment. Alveolar lamina feebly developed, inferior lamina with very distinct puncta in quincunx, foiming about 12 striae in 1 c.d.m. Diameter of valve, 7 to 18 c.d.m. Marine. — Found in the same localities as the preceding, but is not so common. GENUS 158.— TRUANIA PANT., 1886. Valve disciform, with strong puncta, divided into cuneate com- partments by the interposition of raised plicae. Umbilical area covered with coarse scattered blurs. This genus only comprises a single form T. ArcJiangelskiana Pant, from Archangel, Russia, a figure of which is given (fig. 238) drawn from my photo- graph, taken from the original specimen Fig. 238.— rntania Archangehkiana, of the author. GENUS 159.— ACTINODISCUS GREV., 1863. Valves very finely punctate throughout their surface, with the elevated portions finishing in an edge (which gives the appearance of spokes of a wheel), and terminated by a coarse ocellus or pseudo- nodule. This genus includes two species, A Barbadensis Grev., (fig. 239) found in the fossil deposits of Barbadoes and Fig. 2s9.—AcHnodiscus Barbadensi* Oamaru, and A. Atlaniicus Kain and Schultze, which has only 4-6 rays, and is found in a fossil state at Atlantic City, "New Jersey, U.S.A. 11 493 ANTHODISCUS. GENUS 160.— ANTHODISCUS, Grove and Sturt, 1887. Fig. 240. — A nlhodiscus floreatus. Valve with numerous marginal compartments, separated by septiform depressions ; umbilicus rounded, hyaline. Intermediate portion finely punctate, with puncta radiating, interrupted at a certain distance by blank spaces. A single species. A.floreatus Gr. and St., fossil in the Oamaru deposit. Figure 240 repro- duces my photograph of this beautiful form. GENUS 161.— ACTINODICTYON PANT, 1889. Valve with unequal compartments; the elevated compartments very narrow, terminated by a process ; depressed compartments broad, reticulate, triangu- lar, interrupted at the base by a short elevation elonga- ted into the hyaline umbi- lical portion. Two species both fossil from Ananino, Russia, A. Fio. Weissflo^ii Pant., and A. Actinodictyon antiquorum. antiquoriim Pant. (fig. 24 1 ) photographed from the author's specimens. LEPIDODISCUS. 499 Fig. 242. Lepidodiscus elegans. GENUS 162.— LEPIDODISCUS WITT, 1885. Valve capuliform, with elevated margin, then abruptly concave and after- wards again slightly eleva- ted near the centre. Margins showing numer- ous narrow septiform de- pressions, elevated portions resembling scales, central portion showing, according to different focussings, sometimes coarse granules, sometimes numerous rays varying in number and coarseness. This genus only comprehends a single species, excessively curious and very rare L. elegans Witt. (fig. 242), found at Archangelsk by Dr. O. N. Witt and in Ananino deposit by Dr. Pantocsek. WITTIA PANT., 1889. Valve similar to that of Lepidodiscus from which it principally differs by the striae radiant, flame-like, very finely punctate, oc- cupying the whole median portion of the valve, and by the centre being finely punctate, separated from the median por- tion by a hyaline circle. A single species. Fig. 243. — Wittia insignis. 5°° ASTEROLAMPRE^E. W. insignis Panl., fossil at Ananino, Russia (fig. 243), drawn from my photograph of Dr. Pantocsek's specimen. This genus appears to me to be very closely approximate to the preceding. It will be necessary to examine a larger number of quite perfect valves to identify or differentiate the two genera definitely. TRIBE XXIV.— ASTEROLAMPRE/E. Table of Genera. "Valve furnished with strong internal costae, united to one another at the centre and sides by a robust internal lamina, centre hyaline ( Valves hyaline, angular or circular, without costas or straight rays not enlarged near the margin or near the centre, and not touching the margin Arachnoidiscus. . Liostephania. fDisc radiated, punctate, cellular or granular, with centre granular, not stellate, with marginal portion divided into numerous compartments by enlarged costae in the form of spokes of a wheel f Valves inflated, hyaline or punctate, with centre sometimes stellate, rays linear, more or less bifurcated and somewhat irregular ; inter- spaces hyaline or with flexed or sinuous lines f Valves hyaline, divided by simple rays ; centre hyaline or granu- lar, reticulate, or finely punctate . Gyroptychus. Cladogramma. 2^ o o -i a ,-• be a o o . c P. IT, ,0 f Rays simple, straight, never reaching to the centre ; puncta more or less large and scattered Mastogonia. Stietodiscus. Rays irregular both as to length and division, often divided dichotomously ; valves with cells small, uni- form throughout the surface . . . Radiopalma. o B O O V a o £ g as mk 8 ST Rays straight, marginal portion of the valve punctate, and traversed by sectors, radiant, verv narrow Stelladiscus. Rays curved like the letter S ; valve completely hyaline . Gyrodiscus. rt 2 a 3 'o S ! < rt 5 •J - < 0 E ; « p ■ h^ <%\ a/5 I o ra as w o Valve with hyaline area, divided by straight rays, arising either from the centre or from a central rosette and terminating at the base in areolated marginal segments ; such segments being formed by the subdivision of the margin, aided by the continuation of the hyaline area Asterolampra. Valves as in the preceding, but with two com- partments approximate and one ray narrower, interrupted, not going beyond the centre . Asteromphalus. 05 I Valve showing robust septa, radiant, concentric circles of cells and with Asterodiscus. I I I I I Valve as in Asterolampra, but with only two rays and I these inflated near the central rosette . . Rylandsia. LIOSTEPHANIA. 5°I LIOSTEPHANIA EHR, 1847. Valves hyaline, angular, or circular, without costae or straight rays, not enlarged near the margin, or near the centre, and not touching the margin. In the text will be found (fig. 244) a drawing of Liostephania magnified Ehr., found in the Barbadoes deposit. Fig. 244, — Liostephania magnified. We are far from a full knowledge of the genus Liostephania, and I am much disposed to believe that they are internal valves of forms not yet determined, probably of an Asterolampra. GYROPTYCHUS AD. SCHM., 1890. Fig. 245.- — Gyroptychus contabulatus. Disc radiating, punctate, cellular, or granular, with centre granular, not stellate, marginal portion divided into numerous compartments by costae, enlarged in the form of spokes of a wheel. Gvroptychus contabulatus (fig. 245) is Dr. Adam Schmidt's figure. I think this also is an internal valve, probably of an Actinopiychus. ro2 CLADOGRAMMA. GENUS 163.— CLADOGRAMMA EHR., 1844. Valve discoid, with margins and centre raised, hyaline or punctate, centre sometimes stellate, rays linear, more or less bifurcated, and somewhat irregular ; interspaces hyaline, or with curved or sinuous lines. Fig. 246. Cladogramma Cebuense. This genus includes four species, three of which are fossil and all four circular. I give above (fig. 246), CL Cebuense Grun., which is found in the island of Cebu (Phillippine Islands). GENUS 164.— MASTOGONIA EHR., 1844. Fig. 247. — Mastogonia Crux. Valves hyaline, divided by simple rays, centre very small, almost obsolete, hyaline or granular. Valves convex, without spines. Frustules solitary. This genus is approximate to Stephanogonia which we have placed, in consequence of its spines, with the Melosirece. I give (fig. 247), Mastogonia Crux Ehr., from the Bermuda Archipelego and a specimen of which from Richmond (Virginia), I have in my possession, GENUS 165. GYRODISCUS. 503 GYRODISCUS WITT, 1885. Valve discoid, some- what cap shaped ; margins very slightly elevated, centre much raised into a conical apiculus, with trun- cate apex. Arising from the apiculus are rays bent in op- posite directions near the two apices of the Fis:. 248. — Gyrodiscus Vortex, j. 0 & 4 J same diameter. Sur- face of valves very delicately granular, apparently hyaline. This genus includes only two species, G. Vortex Witt. (fig. 248) found by Dr. Witt, at Simbirsk, and by Dr. Pantocsek, at Kusnetzk, and G. Hungaricus Pant., found in Hungary by Dr. Pantocsek. Group Asterolampra (Ehr., 1844), Ch. em. — Valve with hyaline area, divided by straight rays, arising either from the centre, or Irom a central rosette, and terminating at the base in areolate marginal segments ; such segments being formed by the sub-division of the margins by means of a continuation of the hyaline area. The Group Asterolampra comprehends the genera Asterolampra Asterotnplialus, as well as the doubtful genus Asterodiscus and the pseudo- genera Actinogonium and Liostephania. The genus Actinogonium consists of the internal valves ot Asterolampra, and by examining carefully several valves of Asterolampra these internal valves can be seen. They can also be recognised by the figure given by Greville of his A. punctata (T.M.S., 1862, pi. 8, fig. 32). The figure in the text (fig. 249) represents a similar internal valve, which Ehrenberg has named Actinogonium Seplenarium. Fig. 249. — Actinogonium Septetiarium. 504 ASTEROLAMPRA. GENUS 166.— ASTEROLAMPRA EHR., 1844. Rays all equal or emanating from the centre of the valve. This section consists of 36 species, the greater part of which are fossil, and most are found in the Barbadoes deposit. Fig. 250 represents one of the forms living at the present day, A. Grevillei Wall., var. Adriatua Grun. Fig, 250. — Asterolampra Grevillei var. Adriatica. GENUS 167.— ASTEROMPHALUS EHR, 1844. Fig. 251. — Asteromphalus reticulatus. Valve having two of the compartments punctate, approximate, separated by a narrower ray, and on one side not going quite to the margin, and on the other side often going beyond the centre of the valve. About forty species of Asteromphalus have been described, a good number of which are still found living, many also in the Arctic Ocean as well as in the tropical seas. Some species are very cosmo- politan, such as A.flabellatus (Bwb.) Grev., the only species which has been met with in the North Sea (at Teignmouth by Grove), in Ascidians, and also found in Campeachy Bay, Yokohama (Japan) as well as in Corsican moss, from the Mediterranean, in Peruvian Guano, and in the Java Sea. Asteromphalus flabellatus (Breb.) Grev. is characterised by its sub-elliptical valves, its conical finely reticulated compartments, often transversely truncate, and by its median ray straight or very gently curved. Its diameter varies from 4 to 6 c.d.m , the minor axis never being more than 4 to 5 c.d.m. Figure 251 represents A. rcticulati/s Cleve, remarkable for the large cells of its compartments. It is found in a living slate at Java. STELLADISCUS. 505 GENUS 168.— STELLADISCUS RATTRAY, 1890. Valve circular, without rosette or central space. Rays straight, clavate, arising from the hyaline centre, where they are much elongated. Marginal portion (occupying the outer two-thirds of the valve) divided into 12 punctate compartments. This genus only comprises a single species, Stelladiscus Stella Ratt. (Asterolampra Stella, Norm.), figured in the text after Norman. Fig. 252. — Stelladiscus Stella This diatom should be found at Sierra Leone, according to Norman, who, however, only saw one specimen, and no one since him has again seen this singular form. Asterodiscus, Johns, 1852, in Amer. Journ. So., 1852, p. 33, is a very doubtful genus. According to the author it should be characterised by similar valves, with central ray bifurcated, and there should be three species, A. quinarius, senarius, and nonarius, according as it has 5, 6, or 9 rays. As these forms are not figured it is impossible to know what Johnson has seen. GENUS 169.— RYLANDSIA GREV., 1861. Valve disciform, with cellular structure, cells interrupted by two opposite rays surrounded by a hyaline space, very dilated at the base, not reaching to the centre of the valve. A single species : R. biradiata Gr, (fig. 253), which is found in the Barbadoes deposit. It is a very rare form ; the figure in the text was drawn from one of my photographs. Fig. 253. — Rylandsia biradiata. So6 STICTODISCUS. GENUS 170. b STICTODISCUS GREV., 1861. Valve disciform or angular, with median portion inflated, inflation unequal in the two valves ; centre more or less hyaline ; the remainder of the valve more or less strongly punctate, puncta arranged in radiant rows, separated by plicae. Fig. 254. — Stictodiscus. a. S. Kittoniatius f girdle face J. /'. 5. Johnsonianus (valve). This beautiful genus includes about 50 species, the greater number of which are fossil. In the text will be found, after Greville, the valve of S. Johnsonianus Gr., and the girdle face of S. Kittonianus Gr. These two species are fossil, the first is found in the Naparima deposit (Trinity Island), the second in the deposits of South America, specially Nottingham, Richmond, &c. GENUS 171.— ARACHNOIDISCUS EHR, 1849. Fig. 255. — Arachnoidiscus ornatus. RADIOPALMA. 5°7 '@®®G Valve circular, convex, with umbilicus raised, projecting, con- solidated internally by a row of robust costal united to one another by a marginal lamina and a central circular plate, pierced and raised in the shape of a funnel at the umbilicus, and sometimes also by costas more delicate, concentric and transverse to the first mentioned. Valve, properly speaking, formed of two plates (?) one robust, show- ing large thinnings in the form of irregularly quadrate holes, and forming concentric rows ; the other showing fine granules, mostly corresponding to the thinnings of the other lamina. The Arachnoidiscus are amongst the most interesting diatoms known. Nine species have been described, many of which appear to us to be only varieties. The most characteristic and best known are A. ornatus Ehr., and A. Ehrenbergii Bail, and Hat v., which are figured in the text (figs. 255 and 256), the general outline and structure being taken from my photographs. The latter Arachnoidiscus has erroneously been stated by William Smith as belonging to England. All the Arachnoidiscus found are either fossil or from the tropical seas. GENUS 172.-RADIOPALMA BRUN., 1891. Fig. 256. Arachnoidiscus Ehrenbergii. Valve sub-circular, very delicate, with hexagonal striation interrupted by plaits more or less marginal, often divided dichotomouslv. Fig- 257. — Radiopalma dichotoma- 508 RAPIOPALMA. A single species : Radiopalma dichotoma Brun., found in the fossil deposit of Moron (Spain) and drawn in the text (fig. 257) after my photographs. I have in my possession a similar form, but with larger cells, and plaits more regularly marginal, coming from Chalky Mount, Barbadoes (Weissfiog). Awaiting a more minute examination I give it the name of R. Branii, H. V.H. I am tempted to believe that the Radiopalma are only external layers of valves of some form that has not yet been identified. COSCINODISCE^. 5°9 Tribe XXV. — Coscinodisce/E. TABLE OF GENERA. A. — Valves disciform, oval or elliptic. ^ o • f Valve with cellular structure 1-3 -CT3 J. Structure not cellular. -I f Valves punctate, with scattered puncta, and furnished with sinuous-reticulated lines I, Valves quite hyaline, furnished with stiff erect spines ' Valves furnished with a projecting irregular ridge ( £ >? . f Valves with puncta arranged in radiating rows, interrupted by hyaline spaces ; centre often bulbous or with thinly scat- tered puncta, no marginal spines, margin hyaline 3 -5 o 4-* .S 0 H.<" J §3^1 Valve delicate, small ; centre hyaline, granular, and with a u T3 bfl o u a, o >> o o 2 ^ circlet of marginal teeth r 5; -j ■a Jc is o m c o •2j= Valve having a conspicuous pseudo-opening at the centre . . . ■ ■ ' Valves cellular, with a broad margin, with structure different from that of the centre, from which it is separated by a well-defined margin, without spines bfl 'S c o Pyxidicula. Liradiscus. Xanthiopyxis. Acantiiodiscus. Cosmiodiscus. Stephanodiscus. Porodiscus. Craspedodiscus. r bo ( '— in > O > ■n t/5 u "2 .§ rt"3 .- a, Valve having a row of large cells entirely marginal . Heterodictyon. Large oblong cells arrang- ed in (estoon . Brunia. nS > > •5 £ Large cells forming a ring, which separates the centre from the broad marginal btrder ; centre cells arranged in curved or spiral lines . Valve very finely punctate, showing on two sides, about a third from the mar- gins, an arc of pseudo-cells. The two arcs united to one another by a row ^ of spines .... ( Valve having a marginal or submarginal pseudo- nodule ; puncta in radiating rows of unequal length, leaving usually subulate blank spaces Brightwellia Janischia. Actinocyclus. o -a Valves dissimilar, the superior with rows of puncta in distant lines, alternately long and short ; inferior valve with puncta in approxi- mate rows of equal length . . Anisodiscus. : -a : o • c ' Valve disciform, punctate or cellular, without any costse, septa or processes whatsoever, except sometimes some very small teeth c3 > Coscinodiscus. Valves furnished with long horns, more or less robust .... Gossleriella. 5i° PYXIDICULA. B. — Valves linear, rcniform, or cuneate. Valves cellular, similar to Coscinodiscus, but reniform .... Stoschia. f Valves elongated, linear or somewhat cuneate, with scattered puncta . Willemoesia. f Valves arcuate, at least on the dorsal side, and marked with more or less scattered, often very coarse, puncta ; girdle face straight .... Leudugeria. Valves not reniform,' Valves arcuate or J linear, | cuneate. -rr , . f Valves cellular, furnished with a small Valves not arcuate : pseudo-nodule on the ventral margin . Euodia. ^, ' ' Valves with radiating stripe, very delicate ; ventral and dorsal margins usually fur- ( cuneate. ^ nished with small teeth ' . . Palmeria. Sect. I. Pyxide/e.— - Valves inflated, convex, in the form of a pyxidium or shaving box. GENUS 173.— PYXIDICULA EHR, 1833. Fig, 258, — Pyxidiada Mediterraneum. Fig. 259. — P. [Dictyopyxis) brevis, Frustules with connecting zone very narrow. Valves convex, disciform, or capuliform, without teeth or central spines, sometimes with small marginal teeth. This genus, in which we include the genus Dictyopyxis of Ehrenberg, consists of a few species which are specially differentiated from Stepha?wpyxis (Meiosirece) by the absence of central teeth which unite the frustules to one another. We give in the text P. Mediterraneum Grim. (fig. 258), and Dictyopyxis brevis Grev. (fig. 259). LIRADISCUS. 511 GENUS Hi.— LIRADISCUS GREV, 1865. a. b. Fig. 260.— Liradiscus ovalis. a. Girdle view. b. Valve view. Fig. 261 — Liradiscus ellipticus. Valves circular or elliptic, convex, sinuous-reticulate, more or less bristling with spines. Connecting zone narrow. This genus includes seven curious species, the greater part fossil. Figure 260 representing Liradiscus ovalis Gr., and fig. 261. L. ellipticus Grev. will give an idea of the genus. Figure 262 represents Epithelion curvatum Paul., which does not appear to me to be differentiated from a Liradiscus. Dr. Pantocsek, in a letter to me of the 26th February, 1894, defines his genus Epithelion as " Frustule oblong, oval, convex, with epithelioid or punctate-spinous structure." Fig. 262. — Epithelion curvatum. 5*2 XANTHIOPYXIS. GENUS 175.— XANTHIOPYXIS EHR, 1844. wi wm&SF m v-j mm ilj§l r f ^ V 1 V- ^ ^ ^ mm W v • ; . .V ■ ", *\ %m mm -\y % •a Fig. 263. — Xanthiopyxis umbonata. Valves entirely hyaline, circular, or elliptic, bristling with short spines, robust and erect. This genus comprises a dozen curious species, all fossil. We give (fig. 263) X. umbonata Grev., found in the Monterey deposit. GOSSLERIELLA. 51. GENUS 176.— GOSSLERIELLA SCHUTT, 1893 Fig. 265 — Gossleriella radiata, Fig. 264. — Gossleriella tropica. Frustule disciform ; valve orbicular, having a marginal crown of gibbous prominences, bearing straight elongated robust spines, with smaller spines scattered between them. This genus which belongs to the Xanthwpyxidece, according to De Toni, has a vague resemblance to Coscinodiscus Sol. I should not like to affirm decisively that it is a diatom. Only a single form, G. tropica Schutt (fig. 264), the hairs of which are of the same length but of an unequal thickness, and G. radiata Schutt (fig. 264), the hairs of which are of a very unequal length. KK 5*4 15RIGHTWELUA. Sect. II. Brightwellie.e. — Valves cellular, with one or more rows of marginal or sub-marginal cells, differing (generally much larger) from the other cells of the valve ; or with the sculpture of the median portion different from that of the margins. GENUS 177.— BRIGHTWELLIA RALFS., 1861. Valves circular, with cellular structure ; cells unequal, those of the margin smaller than those of the centre, and separated from one another by a ring of much Fig. 266, — Brighhvellia hyperbvrea. larger cells. This beautiful genus possesses seven species, which are all fossil, two of them (including B. hyperborea Gritn.), (fig. 266), have also been found in marine dredgings or soundings. GENUS 178.— HETERODICTYON GREV., 1863. Valves circular, finely punctate, with a central rosette of medium sized cells, and a ring, quite margi- nal, of large elongated cells. This genus consists of a single species, H. Rylandsianum Grev., figured in the text, found in the Cam- bridge Estate Deposit, Barbadoes, by C. Johnson. Fig. 267. — Ilcterodictyon Rylandsianum. CRASPEDODISCUS. 515 GENUS 179.- CRASPEDODISCUS EHR, 1844. Fig. 268. — Craspedodiscus insignis. Valve usually circular, with cellular structure, having a broad border of structure different from that of the centre, from which it is separated by a well-defined margin, without spines. I give in the text, after Dr. Ad. Schmidt, a figure of Cr. insig?iis, A. Schm. This form has been found at Nankoori, in the Nicobar Islands. Authors have described about 20 species belonging to this genus. Those most frequently met with in collections are C. Coschiodiscas EJir., and C. elegans E/ir., both fossil, and found in the fossil deposit of Nottingham, Maryland. In the forms which I have been able to examine, it is a depression of the valve which produces the singular appearance which is characteristic of the genus. 5^ PORODISCUS. GENUS 180.— PORODISCUS GREV, 1863. .««flse?37sg Fig. 269. — Porodiscus elegans (girdle view) . Fig. 270. — Porodiscus splendidus (valve view). Valves elliptic, circular, or rhomboidal, with cellular or coarsely- punctate structure, showing at the median portion a pseudo-opening — in reality a depression — the bottom of which is either hyaline (?) or more or less finely punctate. I give, after Greville, the girdle face of Porodiscus elegans (fig. 269), and the valve face of P. splendidus. From an examination of the forms in my collections, I cannot see any difference between the Craspedodiscus and Porodiscus, except that in the latter the depression is deeper and smaller. I therefore agree with the opinion of Mr. Grunow, who ranks the Porodiscus with the genus Craspedodiscus. About a dozen forms have been classified as Porodiscus, all of which are fossil, with the exception of P. Stolterfothii Cast. ERUNIA. 517 GENUS 181.— BRUNIA TEMPERE, 1890, Fig. 271. — Brunia Japonica. Valves circular, finely punctate, or with delicate cellular structure, bearing at a certain distance from the margin a row of coarse oblong or semi-circular cells forming a festooned line. The following is Mr. Tempere's description of this remarkable genus : — "Diameter, -380 mm. (The diameter is very variable in size, the largest specimens being quite double the smallest). Valve face almost plain, gently 5*8 P.RUNIA. rising in order to bend back at a right angle, thus forming a rather elevated wall or prominent margin, which is reflected in the same direction as the superior portion, but inclining more or less outwards, to form a gently convex edge of variable size. The general form of the valve is very similar to that of a plate whose rather deep side is at a right angle with the bottom. On the margin and at its intersection with the wall is found a row of coarse oblong cells with a rounded outline placed end to end, and forming a broken but uninterrupted line, giving the appearance of a festoon surrounding the base of the wall. This corona of coarse cells is lodged in a channel formed of two silicious plates ; one of these being a continuation of the valve, and the other, exterior, which is extremely thin, follows the undulations, which form the cells, and is very finely punctate. This arrangement of the coarse cells is more evident in fragments inclined in the same direction as the margin on which they are placed. Dimensions of one arch of the corona "003 mm. Between each cell is found a cavity or depression of the valve; this regular depression produces an undulated plait which surrounds the corona of cells. Superior surface of the valve : Diameter '310 mm., with radiant and punctate striation, 5 to 6 striae as a mean in 'oi m., and formed of small beads increasing in size as they approach the centre. No distinct area. Rays ending between each pair of coarse cells. The punctate lines and the rays continue the whole length of the wall as far as the cells ; outside that, only the punctate lines are continued, and the puncta are more accentuated. The silica of the cells is very robust, while that of the rest of the valve is very thin and flexible, resulting in only fragments of this species being found. Its colour is drab yellow. Habitat — Limestone from Japan. Mr. Tempere describes two species in this genus, B. Japonica Temp., figured in the text (fig. 271), taken from a photograph which Mr. Tempere has been good enough to send me, and Brunia mirabilis Temp., also coming from Japan, and which differs from the first by the absence of rays. I have in my possession a specimen of this form from Sta. Monica, where it was found in 1878, by Mr. Weissflog. ACANTHODISCUS. 5*9 Sect. III. Acanthodisce^;. — Characters of the genus. GENUS 182.— ACANTHODISCUS PANT, 1892, in litt. Valve convex, with coarse scattered puncta throughout, between the centre and the margin a rugose, dentate ridge, more or less interrupted or plicate. Fig. 272. — Acanihodiscus Clypeolus In his " Diatomees nouvelles, 1891," Professor Brun established a genus called Cotyledon, based especially on the presence of a ridge. Prof. De Toni has suppressed this genus because a genus of the same name already existed. This does not appear to me to be a sufficient reason, as there can be no confusion possible between a phanerogamic genus and one of diatoms. But the genus of Mr. Brun, as the learned diatomist himself subsequently stated, was only given as a landmark, and it includes very different forms. I therefore think it is more convenient to adopt the genus which Dr. Pantocsek has communicated to me, and to which he gives the name of Acanthodiscus, and which is founded as much on the striation as the presence of the ridge. The genus Acanthodiscus therefore includes two species, A. clypeolus (Brun.), a variety of which will be found figured in the text (fig. 272), drawn from one of my photographs, and A. rugosus Pant. Both have been found fossil at Kusnetzk, Russia. As to the curious form which Mr. Brun calls Cotyledon coronalis it requires further examination, and may constitute a new genus, Brunictta H. V.//., in which may also perhaps be included his C. circutaris. 520 STEPHANODISCUS. Sect. IV. Hyalino-radie/E. — Valve furnished with radiating hyaline spaces. GENUS 183.— STEPHANODISCUS (Ehr., 1845), Emend. Grun. a. Fig. 273, — Stephanodiscits Niagara?, a. Girdle view. b. Valve view. Valve circular, somewhat convex, with margin furnished with a corona of spines, simple, acute, with fine puncta arranged in radiating rows, interrupted by smooth spaces radiating, simulating lines ; centre with scattered granules. In this genus have been arranged a rather numerous series of forms, most of which probably do not belong to it. In the text will be found the type- form of the genus S. Niagara" Ehr., found living at Niagara, and also at Franz Josef Land. It has also been found in a fossil state at Buffalo and in Prussia. S. Hantzschianus has been recorded in Belgium. S. Hantzschianus Grun. (Arct. Diat., p. 115; H.v.H. Atl., pi. 95, f. 10*; Type No. 482), plate 23, fig. 662. Valve small, with rather robust marginal spines, 6 to 9 in 1 c.d.m. ; stria? radiant, formed of two parallel rows of very fine puncta, very difficult to be seen. Diameter, 1 to 1*75 c.d.m. Fresh water. — Brussels (Delogne). Antwerp (H.V. H.). It is probable that it will be met with in other countries in our zone. C03MI0DISCUS. 521 GENUS 184.— COSMIODISCUS GREV., 1866. Valve with hyaline margin, puncta arranged in radiating rows, interrupted at various points by hyaline rays ; centre with scattered puncta. This genus, which was included in the Fig. vj^—Comiodiscus tenuis. Coscinodiscus by Rattray, deserves in my opinion to be preserved. The hyaline margin and its rays, equally hyaline and distant, easily determines the species which ought to he included in it. The figure in the text is that of C. tenuis Grun., which is found fossil in the Monterey deposit. GENUS 185. -ANISODISCUS GRUN., 1886. =9 Fig. 275. — Anisodiscus Pantocsekii. Valves circular, furnished with a margin of small distant spines, difficult to see. The two valves dissimilar ; the superior, with rows of puncta in distant lines, alternately short and long, the inferior valve with puncta in approximate lines of equal length. This genus only includes a single species, A. Pantocsekii Grim., found in a fossil state in Hungary, the figure of which is reproduced after Grunow (fig- 275)- 522 ACTINOCYCLUS. GENUS 186.— ACTINOCYCLUS EHR, 1840. V^T^-^-v,, Fig. 276. — Actinocyclus Ralfsii. Valve orbicular, elliptic or rhomboidal- oblong, convex, having a marginal or submarginal pseudo-nodule, frequently furnished with small marginal or submarginal spines ; puncta in radiating rows of unequal length, usually leaving subulate hyaline spaces. Frustule disciform. ANALYSIS OF SPECIES. Valves circular. Valve usually iridescent at a low magnifica- tion, puncta very visible. Hyaline f Subulate spaces very broad, pro- spaces of ducing the appearance of well- the marked concentric zones ; valve \ puncta very vigorous . A. Ralfsii. clearly subulate- Subulate spaces very narrow ; acute. i puncta more delicate . A. Ehrenbergii. Hyaline spaces not subulate ; puncta strong, forming undulated concentric lines . A. crassus. Valve not iridescent ; puncta very delicate ; subulate spaces very feeble or absent . . • ■ -A. subtilis. Valves elliptic . A. Roperii. The genus Actinocyclus includes about 60 species, found mostly in a living state, and inhabiting all parts of the world. ACTINOCYCLUS. 523 A good monograph of this genus was published in 1890 by Rattray, under the title of " A revision of the genus Actinocyclus" to which we refer the reader who desires to study exotic species of this genus. Figure 1:78 in the text represents A. Ralfsii, the type-form of our regions. A. Ralfsii (W. Sm.) Ralfs. (in Pritch., p. 835 ; Eupodiscus Ralfsii IV. St,,., S.B.D., ii., p. 86; H.V.H. Atl., pi. 123, f. 6*; in Type No. 518 and var. in Type No. 516 and var. in Type No. 517), plate 23, fig. 658. Valve circular, with large submarginal pseudo-nodule. Puncta interrupted by very numerous subulate hyaline spaces, arranged in several rows and giving, at a low magnification, the appeaiance of concentric zones; 5 rows of puncta at the middle of the ray at the superior extremity of the innermost zone in 1 c.d.m. Margin furnished with small spines, almost marginal, distant about 1 c.d.m. from one another; puncta very fine, in quincunx, about 14 rows in 1 c.d.m. Diameter of valve, 10 to 13 c.d.m. Marine.— Very rare : Blankenberghe, Ostend, Antwerp (Scheldt, H.V.H.), France (Breb!), England (W. Sm. ! Kitton, Stolt., Comber), Scotland (Cole ! Baxter Coll., No. 2689), Cuxhaven (Bessel), Marstrand (Sweden, Thum. !), Ireland (O'Meara). var. sparsus (Greg.) Ralfs. — Rows radiating, excessively distant at the central portion of the valve (about 8 in 1 c.d.m.) then augmenting regularly and progressively so as to form conspicuous concentric zones. The opinions of authors differ greatly on this form, while Gregory, Ralfs, Kitton, and others see in it only a variety of A. Ralfsii. Mr. Rattiay, on the other hand, thinks right to make it a distinct species, at least provisionally. Marine. — Scotland : Glenshira Sand (Weissflog ! Gregory). A. Ehrenbergii Ralfs. (in Pritch. Inf., p. 834 ; H.V.H. Atl., pl. 123, f. 7 ; Type No. 518), plate 23, fig. 659. Valve circular ; pseudo-nodule very large, submarginal ; connecting zone slightly or not marked ; hyaline spaces very narrow and few ; puncta approximate, 8 radiating rows in 1 c.d.m. Margin with small spines about 1 c.d.m. from one another ; puncta in quincunx, about 16 rows in 1 c.d.m. Diameter of valve, 6 in n c.d.m. Marine. — Blackenberghe, Scheldt at Antwerp (H.V.H.), Cherbourg (Breb.), England, various localities, Cuxhaven (Mbller, etc.). Found on all our coasts. A. crassus H. Van Heurck. (H.v.H. Atl, pi. 124, f. 6 and 8*), plate 23, fig. 660. Valve orbicular, with pseudo-nodule submarginal, and furnished with very small submarginal spines, indistinct in small specimens. Puncta strong 524 ACTINOCYCLUS. at the centre of the valve, becoming finer and finer towards the margins, arranged in radiating rows, forming undulated concentric circles ; about 8 puncta in 1 c.d.m. at the middle of the ray and 18 at the margin, where they are arranged in quincunx. Diameter, 4 to 8 c.d.m. Marine. — Blackenberghe, 2nd Basin, Scheldt at Antwerp (H.V.H.), England (W. Sm. ! Hodgson, Kitton, Stolt. , Norman), Ireland (O'Meara). In the text of the " Synopsis " I have given the form under the following descriptions : — A. craSSUS (W. Sm. !) Ralfs {Eupodiscus crassus IV. Sm., S.B.D., i., p. 24, pi. 4, f. 41*), plate 34, fig. 897. Mr. Rattray, in his Monograph, p. 154, says: "The present species is separated from the Eupodiscus crassus of Smith, owing to the inconspicuous- ness of the fasciculi and the sharpness of the submarginal zone." A further examination has shown me that my form is quite identical with the authentic gatherings, labelled by Wm. Smith himself, in my possession, but that Smith's figure is faulty and shews fasciculi which do not exist in nature. Only in one of the gatherings of W. Sm. at most can there be recognized, under low magnification, a vague arrangement of puncta in radiating lines. I have consequently modified the name of this in accordance with Rattray and De Toni. A. Subtilis (Greg.) Ralfs. (in Pritch., p. 835; Eupodiscus subtilis Greg. ; Diat. of Clyde, p. 29, pi. 3, f. 50 ; H.V.H. Atl., pi. 124, f. 7*, Type No. 519, and var. Type No. 520), plate 23, fig. 661. Valve yellowish, almost hyaline, not iridescent ; pseudo-nodule submarginal, less visible than the preceding species. Striae radiating, about 13 or 14 in the middle of the ray, finely punctate, leaving hardly any subulate hyaline spaces. Margins with small spines distant about 75^, with strire somewhat more compact. Diameter of valve, 5 to 9 c.d.m. Marine.— Not yet observed in Belgium. England, various localities (Weissflog, W. Arnott, Kitton, Norman), Scotland (Greg.). A. Roperii (Breb.) Kitt. (Bull. Soc. Beige. Micr., 1878, p. 30; Eupodiscus Roperii Breb. ; Coscinodiscus (?) ova/is Roper ; H.V.H. Atl., pi. 125, f. 5, 6*), plate 34, fig. 898. Valve greyish, rounded-elliptic, with margin furnished with a crown of processes enlarged at the summit, striae delicately punctate, arranged in COSCINODISCUS. 525 conspicuous fascicles, preudo-nodule indistinct. Centre with puncta in irregular concentric rows. Striae about 16 in 1 c.d.m. near the middle of the ray ; length of minor axis of valve, 3 to 4 c.d.m. ; major axis 4 to 6*5 c.d.m. Marine. — France (Normandy, Breb!), England (Deby, Norman), Scotland (W. Arn. ! Rattray). Sect. V. Eucoscinodisce^:. — Valves with similar structure throughout the surface. GENUS 187.— COSCINODISCUS EHR, 1838. Fig. 278. — Coscinodiscus excentricus. Fig. 277 .—Coscinodiscus Asteromphalus var. consticua. Valves circular or elliptic without any process (sometimes with small submarginal teeth), costae or septa. Structure alveolate or punctate. Frustule disciform. The genus Coscinodiscus is in a more confused state than any other. It comprises not less than 300 species, on the value of which authors are far from being agreed. The genus has been the subject of three important 526 COSCINODISCUS. works by Mr. Grunow, Mr. Rattray, and Mr. J. D. Cox. It will be convenient to make a few remarks about each. The work of Mr. Grunow will be found in his important publication Die Diatomcen von Franz Josefs Land. Mr. Grunow there arranges the Coscinodiscus into two principal groups, the Radiati and the Fasciculati, to which is added a third small group the Pseudo stephanodisci. He admits into each group a limited number of principal forms or species, to which he attaches a considerable number of varieties or sub-varieties. Mr. Grunow states that the difference, the delimitation of species, is extremely difficult in consequence of the innumerable transitional forms which knit together the large groups. In this way is the Radiati, which are characterised by the cellular structure ; in many species the cells pass into puncta. Mr. Grunow's work is one of considerable importance, in which the stamp of a master is clearly recognizable, and I advise anyone who desires to devote himself to the Coscinodiscus, to study it thoroughly. Mr. Rattray has published "A revision of the genus Coschiodiscus and some allied Genera," a volume of 240 pages, and a work of great importance. Mr. Rattray introduces into the genus Coscinodiscus several allied genera, which are easily distinguished, and which consequently deserve to be preserved, if only to facilitate their determination. In any case, Mr. Rattray's work gives in a condensed form all that is known of the Coscinodiscus, and it would be impossible to devote oneself to this genus without recognizing the work of this skilful monographist. The third work, which is not the least original, has been pub- lished by Dr. J. D. Cox, under the title of "The Coscinodiscae ; Notes on some unreliable criteria of genera and species." The Hon. J. D. Cox, starting from the same point of view as many well-known diatomists, deplores the immense number of forms which have been created in the genus Coscitwdiscus, and he proposes to refer all the Coscinodiscus to seven forms, which are as follows : — 1. Actinocyclus Ehrenbergii Ralfs. — The disc is divided into compartments or segments by radial lines of alveoli, at the marginal end of which is a small spine. Each compartment is filled by a fascicule of lines of alveoli, of which the middle line is radial and the other lines parallel to the middle one. The outer rim is bevelled or curved sharply beyond the spines, and upon this are more numerous lines of finer alveoli, making decussating as well as radial striae. A "pseudo-nodule" is near the margin. 2. Coscinodiscus subtilis Ehr. — Marking of the disc like the last, except that the radial lines between the fascicles are omitted, and the parallel COSCINODISCUS. 527 lines of the wedge-shaped fascicles are lengthened till those of adjacent fascicles touch. The small spine is at the marginal end. of the middle line of the fascicle. Bevelled rim beyond the spines similar to last. No pseudo- nodule. ?. Coscinodiscus radiolatus Ehr. — Marking of the disc similar to the last, except that the fascicles are each formed by a radial line, with parallel lines on one side of it only, the fascicles being all similar to each other and symmetrical. The small spine is at the end of the radial line forming the side of the fascicle. 4. Coscinodiscus lineatus Ehr. — The disc covered with alveoli in straight lines parallel to a diameter and arranged in quincunx, so that where the round alveolus becomes hexagonal the surface of the disc resembles a true honey-comb, the most prominent lines in appearance being parallel to the given diameter ; a loose circle of small spines marginal or intra-marginal. 5. Coscinodiscus radiatus Ehr. — Marking of the disc made up of hexagonal alveoli in radial lines, which, starting from a central rosette, bifurcate as they go outward, so that there are rarely continuous straight radial lines of alveoli. In robust specimens the upper surface of each alveolus has a dotted appearance, caused by finer secondary pits or marks. 6. Coscinodiscus centralis Ehr. — Marking of the disc of hexagonal, round or subquadrate alveoli, which, starting near the centre, go outward in continuous radial lines, new radial lines being intercalated as room is made by the outward divergence. Secondary maiking in robust specimens: in large examples the central zone is thin, and the outer zone relatively robust and thick. 7. Coscinodiscus marginatus Ehr. — Marking of the disc sub- hexagonal, alveoli without traceable scheme of radiation, but in largest specimens approaching Cos. radiatus. Margin strongly recurved and produced, so as to make a more and more deeply cup-shaped valve in each new frustule formed by fission, the small valves being thus most deeply cupped in a given brood, and the large valves most flat. I have already several times indicated my way of looking at the matter, and I believe that whenever an easily recognised division can be formed — whether called tenus or subgenus or section — it is useful to form it in order to restrict the field of research, and to render easier determinations. Thus 528 COSCINODISCUS. although the reasons given by Mr. Cox are very plausible, I prefer continuing to separate the Actinocydus from Costinodiscus. In addition, I consider that a seventh" form should be admitted (the Adinocydus having been suppressed), namely, C. excentricus E/ir., which is clearly characterised by its rows of eccentric lines. As to the other propositions of Mr. Cox, I frankly admit that they agree somewhat with my own views. Sooner or later it is inevitable that a serious effort must be made to reduce enormously the number of species which are permitted to day. Each further form that is described more or less covers up the differences existing hitherto between certain given species. A time will come, therefore, when it will be necessary to recognize that the number of real species is excessively limited, and the culture method, if that becomes general, will certainly produce material of the greatest value — probably even the only such admissible for the definite solution of the difficulty. But a single cultivation will not suffice for a given form. These must be prolonged and directed — even for a single form — in different directions, and it will be necessary to appreciate the influence of different conditions ot existence. My cultivation of phanerograms enables me to advocate this cause, and better, perhaps, than some others. In fact, in my youth, I closely pursued (and that under the direction of Maitre) the cultivations at the Ecole Jordanienne ; I studied with Jordan those innumerable species created at the expense of Draba vema, and many other Linnean forms, and the lessons which I then received have not a little contributed to destroy any illusions, and to give me, with regard to diatoms, ideas similar to those of Messrs. J. D. Cox, Ham, L. Smith, etc. But meanwhile, and until sufficient study has enabled us to decide these knotty questions, let us return to the Coscinodiscus of our coasts. I shall give the forms now admissible within reasonable limits. The following table will show that these forms are not very numerous in the limited region adopted for this work : — COSCINODISCUS. 529 ANALYSIS OF SPECIES. Valve with coarse granules, smooth space small Valves having a smooth hyaline rounded space in the centre. ") Valve with very fine puncta, smooth space large o Q. ° - 2 i c C 5 ^d 6*), plate 23, fig. 665. Valve circular, with margins furnished with small spines, and sometimes a small process {var. leptopus Grim.) ; alveoles arranged in series forming straight lines in all directions, and in the rather extensive marginal zone much smaller than in the middle of the valve. About 7 to 7*5 series of alveoles in 1 c.d.m. Diameter, about 3 to 10 c.d.m. Marine. — Blankenberghe, 2nd basin (H.V.H.). Devonshire, England (Baxter Coll., No. 2841). Ireland (O'Meara). Group III. Punctati. — Valves with puncta only. C. nitidus Greg. (Diat. of Clyde, p. 27, pi. 10, f. 25; H.V.H. Atl. Supp., f. 41*), plate 23, fig. 667. Valve circular, with very large and very distant puncta, forming more or less radiant lines. Puncta on margin small, arranged in two concentric rows, about 6 to 7 in 1 c.d.m. Diameter, 4 to 5 c.d.m. in the specimens observed. Marine. — Rare. Blankenberghe, 2nd Basin (H.V.H.), England (Kitton). Cumbrae, Scotland (W. Arnott). Lamlash (Gre v., Greg.). Ireland (O'Meara). Hvidingsoe (A. Schm. ). C. Subtilis (Ehr. ?) Grun. (Kaspisch. Meer, p. 27; Diat. Franz. J. Land, p. 29, pi, C? f, 26*), plate 34, fig. 901. coscinodiscus. 533 Valve circular, margin not spinous, alveoles small, easily seen to be puncti- form, arranged in fasciculate rows. Marine. This type-form is represented in our region by the following varieties : — var. Normanii Greg. (Coscinodiscus fascicu/atus, A. Sclun. ; Coscino- discus siibtilis, Eul., No. 115; H.V.H., pi. 131, f. 1*), plate 23, fig. 668. Valve without spines, alveoles small, very small at the margin ; rows of alveoles bifurcating so as to form, near the margin, fascicules, consisting of 6 rows; near the margin, 9 rows of alveoles in x c.d.m. Diameter of valve, 3-5 to 7 c.d.m. Marine. — Frequent. Blankenberghe, Antwerp (Scheldt, H.V.H.). Hull, England (Norman). Ireland (O'Meara). Holstein (Moller) var. Rothii Grun ! (Cose. Rothii Grun., Kasp. Meer, p. 28; H.V.H., Types Nos. 532 and 533). Valve small, with margin furnished with small spines placed just at the middle of the fasciculi ; about 12 stria? in 1 c.d.m. at the margin of the valve. Diameter, 2*5 to 3*5 c.d.m. Marine. — Antwerp, very frequent in the Scheldt C. laCUStris Grun! (Diat. Fr. J. Land, p. ^, pi. D, f. 300; Cyciotclla punctata IV. Stn.; H.V.H. Ati. Suppl., f. 42*; in Type No. 535), plate 23, fig. 669. Valve orbicular, undulated at the side, with margin furnished with small spines, approximate (6 in 1 c.d.m.), and very distinct. Puncta fine, arranged in radiating rows, divided dichotomously. About 10 to 11 rows in 1 c.d.m. at the margin of the valve. Diameter, 1*5 to 6 c.d.m. Fresh water. — Deurne, near Antwerp (P. Gautier). England: Market Weighton (Norman, Grunow), Yorkshire, Wisbeach (W. Sm.), Breydon (Kitton). C. punCtulatUS Greg. (Diat. of Clyde, p. 28, pi. 2, f. 46*), plate 34, fig. 904. Valve with radiating striae, very fine (about 20 to 22 in 1 c.d.m.), scarcely visible towards the centre of the valve, intermixed with coarse scattered puncta. Margin striate and clearly defined. Diameter, 4-5 to 8-5 c.d.m. Marine.— Lamlash Bay and Loch Fine, Scotland (Greg.), Ireland (O'Meara). Note. — Gregory has referred this form to the Coscinodiscus with doubt, and believes that it may be a valve of Meiosira. Walker Arnott in his manuscript 534 COSCINODISCUS. and notes, as well as Eulenstein, considered it a Podosira. I am equally of opinion that it not a true Coscinodisais. Planktoniella Schlltt, 1893. — A genus created for Coscinodisais So/, which is distinguished by the membranous ala surrounding the valve, and by the baculiform appearance of the girdle face. This diatom, besides being very rare, deserves to be raised, in my opinion, to the 'rank of a genus. Fig. 279. — Planktoniella Sol. Antelminellia Schiitt, 1893. — A genus created for Coscinodisais Gazelhz of Janisch (plate 34, fig. 902 of this work). This form, which has the structure of C. concinmis, is distinguished by its large size, which reaches almost to 2 mm., and by the small spines found on the central portion. COSCINODISCUS. 535 The following genera are very approximate to the Coscinodiscus and should probably be combined with this genus : — 1 X. . . • • r - • . . COn~ --V ■**« *& ' I*:*:'--. : ^^ °<*^*W.J,^w--~'~ .«-*" Fig. 280. — Ethmodiscus ■punctiger. EthmodisCUS Ca.Str. , 1886 — This genus includes the Coscinodiscus with very fine puncta. Figure 280 in the text shows a form of this genus Ethmodiscus punctiger Castr., which has been found in Yeddo Bay. Haynaldiella Pant., 1892 (Haynaldia Pant. olim). Valve circular, convex, with small plane central area, margin striate, very distinct. Structure striolate, llame-like, with striae forming radiating lines. 536 JANISCHIA. H p Hi m 1 I Fig. 2S1. — Haynaldiella antiqua. A single species, Haynaldiella antiqua rant. (Coscinodiscus strig Hiatus Witt.), represented in fig. 281, which has been found in a fossil state in Russia and in Hungary. GENUS 188.— JANISCHIA GRUN., 1882. Valve circular, finely punctate ; puncta arranged in quincunx, and interrupted near the margin by a row of coarse elongated puncta (processes), surrounded by a small hyaline area. On two opposite parts of the valve the processes are interrupted and replaced by a long semi-hyaline line, formed of coarse puncta, surrounded by smooth spaces. Fig. 282. — Janischia antiqua. JANISCHIA. 537 The genus Janischia only comprises one species, Jr. antiqua. Grim. (Cosd?iodiscus Ludovidanus Rait.), fig. 282, (H.V.H. Atl., pi. 95 bis, f. 10, 11). This is in reality a very peculiar Cosdnodiscus, the structure of which closely resembles Brunia, but with this difference, that in the Janischia the peculiar band does not make a complete circuit of the valve, and has only a very slight development in breadth. StOSchia Janisch (in litteris) is a reniform Cosdnodiscus, which Mr. Rattray has described under the name of C. reniformis. It is represented in the text (fig. 283). Is it a constant form or only a deformed valve? I am Fig. 283. — Stoschia. if unable to answer this question. Mr. Janisch certainly examined this curious diatom in his work on the Expedition of the Gazelle. Numerous examples of this interesting form have been found on the West Coast of Africa. Willemoesia Castr., 1886, is also described by Mr. Rattray as a Cosdnodiscus. I give in the text (fig. 284) after Castracane a figure of Willemoesia humilis Castr. {Cosdnodiscus humilis Rattr.), which has been found in one ol the gatherings of the Challenger Expedition. Its habitat is unknown. Fig. 284. — Willemoesia humilis. 538 EUODIA. Section VI. — Hemidisce^e. GENUS 189— EUODIA BAILEY, i860. Fig. 285. — Euodia gibba. Valve arcuate, with areolate or punctate structure ; cells often radiant, sometimes more or less fasciculate. Margin often furnished with small pseudo-nodule, more or less developed, sometimes reduced to a sub-hyaline spot. Girdle face cuneate. This genus is closely connected with both Eupodiscus and Coscinodiscus ; the cuneate form which is common to this, and the following genus dis- tinguish them from all other approximate genera. It can be further sub- divided into two sub-genera : the Hemidiscus of Wailich, which possesses the pseudo-nodule and a rather fine cellular structure, plainly radiating, and the true Euodia, which are without a pseudo-nodule and have very coarse, more or less scattered puncta. In the text is given (fig. 285) Euodia gibba Bail. {Hemidiscus Cuneiformis Walls), which is found in the West Indies, at Ceylon, Zanzibar, &c. This genus includes about a dozen species, many of which require further examination. GENUS 190.— PALMERIA GREV., 1865. Fig. 286. — Palmeria Hardmaniana . LEUDUGERIA. 539 Valve semi-lunate, finely striate, with margins furnished with small spines, from which arise somewhat more robust striae. Striae radiating, finely punctate, only extending to the centre of the valve, which is smooth. Girdle face cuneate. In the text will be found (fig. 286) from one of my photographs, P. Hardmaniana Grev., with the observation that the robust striae have been exaggerated in the drawing. This species is found in China. GENUS 191.— LEUDUGERIA TEMPERE, 1893. Valve arcuate, with very coarse puncta more or less scattered. Girdle face straight, showing on one of its faces an inflexion at the apices of the valve. Connecting membrane plicate, rather finely pnnctate. I'M ©■ ' UUsS In. S> • ®« • ■ COO J Lijo ;-; t ?ia) 207 crucicula (W. Sm.) (Navicula) 161, 206, 207 and 208, pl. 4, f. 172 var. protracta Grun. 207, pl. 4, f. 173 crucifera Grun. (Navicula) 176, 183, 187, pl. 25, f, 7to cruciformis Donk. (Navicula) 164, 166, pl. 2, f. 75 crucigeruin W, Sm. (Navicula) 231, 232, pl. 5, f. 242 crucigerum IV. Sm. ( 'Schizonema) 231, 232 Crumena Breb. [Surireila) 373 Crux Ehr. (Mastogonia) 502* cryptocephala Ktz. (Navicula) 175, 180, pl. 3, f, 122 var. intermedia, 180 var. exilis, 180, 181, pl. 3, f. 124 var. veneta, 181, pl. 3, f. 123 Cryptocephala II'. Sm. [Navicula) 181 Crypto-Raphidiere 123, 410 crystalia Sommeif, 1827 (No, 27) crystallina (Lyng. ) Ktz. (Synedra) 308, 315, pl. 10, f. 435 ctenophora Breb (No. 40) cunciformis Wall, [llemidiscus) 538 cursoria Do>ik. [Bacillaria) 394 cursoria (Donk.) Grun. (Nitzschia) 393, 394, pl. 33, f. 879 curvata 'Ktz) Grun. (Rhoicosphenia) 275,* pl. 7. f. 319 var. marinum 276, pl. 7, f. 32o curvata Castr. (Thalassiothrix) 322j pl. 30, f. 840 curvatuni Pant. (Epithelion), 511* cuspidata Ktz. (Cymbella), 141, 142, pl. 1. f. 23 var. naviculiformis Auersw. 142, pl. 1, f. 24 cuspidata Ktz. (Navicula), 214, pl. 4, f. 190 var. halophila Grun. 214, p]. 4, f, 191 Cyclophora Castr. 237,* (No. 7) Cyclotella Ktz. 445 (No. 11 1) Cylindrotheca Rab. 409 (No. 83) Cylindrothecea; 400 Cymatogonia Grun. 496 Cymatoneis Cleve. 238 (No. 9) Cymatopleura W. Sm. 364, 366 (No. 77) Cymatosira Grun. 322, 327 (No. 45) Cymbamphora (Amphora) 126, 130 Cymbella Ag. 124, 140 (No. 2) Cymbellere 124 cymbelliformis (A, Sch.) Grun. (Campylosira) 327,* pl. 24, f- 457 cymbifera Greg. (Amphora) 132, 133, pl. 24, f. 678 cymbiforme Ehr. [Cocconema) 147 cymbiformis Ehr. (Cymbella) 141, 147, pl. 1, f. 38 var. parva 147, pl. 1, f. 39 cymbophora Breb. 1838 (No. 2) cymbosira Ktz. 1844 I No. 30) Cyprinus IV. Sm. (Navicula) 185 cystopleura Breb. 1858 (No. 35) Dactyliosolen Castr. Per. em. 412, 416, 419 (No. 85) Dactylus Ehr. [Navicula) 165 Dallasiana IV. Sm. [Cyclotcda) 446 Dalmatica 'Ktz.)Grun. (Licinophora,) 342, 343, pl. 11, f. 459a var. tenella 343, pl. 11, f. 459^ Dalmatica Ktz. [Rhipidobhora) 343 Danica Ktz. (Svnedra) 311 Danica Flog. (Cocconfis) 289, pl. 29, f. 820 Dansei T/nv. [Dickicia) 233 Dansei Thw. (Mastogloia) 153, 155, 233, pl. 2, f. 64 var. elliptica 155 Davyana Grev. (Entogonia) 476 debilis (Grun.) H V. H. (Anaulus) 454, pl. 19, f. 626, pl. 34, f. 892 debilis Gruu. [Eunotogramma) 454 debilis (Arn.) Grun. (Nitzschia) 384, 385, pl. 15, f. 497 Debya Ratt. 1886 (No. 153) Debya (Pant.) 49s (No. 157) Debyi-Leud-Eort. [Pseudo-synedra) 320 decipiens Grun. [A mphoropsis) 267* decipiens Grun. (Coscinodiscus) 532, pl. 34. f. 905 decipiens (Grun.) (Auricula) 267* decora West (Attheya) 420* decorum W. Sm. (Pleurosigma) 250, 254, pl. 6, f. 269 decorus Breb. (Campylodiscus) 376, pl. 14, f. 596 forma minima? 376, pl. 14, f. 597 deformis \V. Sm. [Synedra) 310 delicatissima Lew. (Surireila) 374 delicatissima IV. Sm. (Synedra) 312 delicatula Ktz. (Cymbella) 141, 143, pl. 1, f. 29 delit alula Ktz. (Hya'losira) 363 delicatula Ktz. (Achnanthesj 278, 281, 291, pl. 8, f. 330 delicatula (Laudena) 418 delicatula (Ktz.) Cleve. (Microneis) 291 delicatula (Ktz.) Grun. (Striatella) 362, 363, pl. 12, f. 483a var. rectangulata 362* delicatulum IV Sm. {Pleurosigma) 251 Delognei H.V. H. (Navicula) 232 Delognei Grun. (Nitzschia) 400, 403, pl. 17, f. 567 denaria Ehr. (Perithyra) 492* Dendrella Bory, 1822 (No. 27) Denticella Ehr. 466 (No. 132) Denticula Ktz. 348, 351, (No. 65) Denticula Grun. (Nitzschia) 390, pl. 15, f. 514 var. Delognei Grun. 390, pl. 15, f. 515 denticulatum Grev. (Triceratium) 469 Desmidium Ag. 1828 (No. 64) Desmogonium Ehr. 304 (No. 36) Detonula Schutt. 418 (No 87 Diadema Ehr. (Syndendrium) 427 diaphana IV. Sm. [Cocconeis) 291 Diadesmis Ktz. 229, 234, (No. 7) Diatoma De Candolle 348 (No. 64) Diatomeae 388, 3J8. Diatomella Grev. 352, 353 (No. 66) dichotomum II'. Sm. [Gomphonema) 273 Dickieia Berk. 233 Dickiei (Thw ) Ktz. (Melosira) 440, 444, pl, 19, f. 623 Dickiei Thw. [Orthosira) 444 dicephala W. Sm. (Navicula) 176, 188, pl. 3, f. 138 Dichomeris Ehr. 1872 (No, 189) dichotoma Bran (Radiopalma) 507,* 508 Dicladia Ehr. 412, 426 (No. 92) Dicladia (Ehr.) Castr. (Chretoceros) 427 (No. 92) Dicladiopsis De Toni 1894 (No. 92) Dictyolampra Ehr. 1847 (No. 166) Dictyoneis Cleve 152, 157 (No. 5.) Dictyopyxis Ehr. 510 (No. 173) didyma Ehr. (Navicula) 191, 193, 194, 234, pl. 3, f. 147 Didymae (Navicula) 163, 190, 234 digito-radiala Greg. (Navicula) 176, 184, 185, pl. 3, f. 130 var. Cyprinus 185, pl. 3, f. 131 var. striolata Grun. 185 dilatata Wm. Sm. (Stauroneis) 161 Dillwynii (Agardh.) H.V. H. (Berkeleya) 245, pl. 5, f. 255 Dimeregramma Ralfs. 334, 335, 337 (No. 57) diodon Ehr. (Eunotia) 299, 303, pl. 30, f. 829, 830 Dioraphala Ehr. 1842 (No. 27) Diplamphora (Amphora) 126, 131 Diploneis Ehr. 234 (No. 7) INDEX. 547 directa W. Sm. (Navicula) 176, 189, pi. 25, f. 722 var. subtilis. 189, pi. 25, f. 723 directa IV. Sm. (Pinnularia) 189 dirupta (Greg.) (Cocconeis) 290, pi. 8, f. 343 Disconeis CI. 286, 288 (No. 34) Discoplea Ehr. 1840 (No. in) Discosira Rab. 1853 (No. 109) Discphonia Ehr. 1853 (No. 66) dissipata (Ktz. ) Gran. (Nitzschia) 394, pi. 16, f. 525 var. media 395, pi. 16, f. 526 var. acuta 395, pi. 16, f. 527 Dissipataa (Nitzschia) 383, 394 distans (Greg.) Gran. (Cocconeis) 287, pi. 29, f. 817 distans Greg. (Denticula) 335 distans (Greg.) Gran. (Glyphodesmis) 334, 335, pi. 30, f. 848 distans Ktz (Melosira) 440, 442, pi, 19, f. 616 var. nivalis W. Sm. 443. pi. 19, f. 617 distans (W. Sm.) H.V.H. (.Navicula), 176, 185, pi. 3, f. 133 distans Greg. (Nitzschia) 393, 394, pi. 33, f. 878 distans 11'. Sm. {Pinnularia) 185 distortum W. Sm. (Pleurosigma) 250, 258, pi. 28, f. 799 Ditylum Bailey 412, 424, 425 (No. 90) divergens W. Sm. (Navicula) t68, 170, pi. 25, f. 706 divisum Ehr. (Stylobiblium) 359* Donkinia Ralfs 152, 248, 249 (No. 21). Donkinii Ad. Schm. {Navicula) 194 Doryphora W. Sm. 1852 (No. 7) Druridgea Donk. 429, 448 (No. 113) duplex Donk. Amphiprora) 262 dubia Cleve (Amphora) 128 dubia (Greg. 1 Ad. Schm. (Amphora 126, 128, pi. 24, f. 672 dubia W. Sm. (Nitzschia) 388, 389, pi. 15, f. 508 dubia Greg. (Stauroneis) 161 Dubiae Nitzschia) 383, 388 Echenets Ehr. (Carnpylbdiscus) 377, pi. 14, 1*. 600 Echeneis Ehr. {Coronia) 377 Echinaria Ktz. 1844 (No. 40) Echinella Lyng. 1819 (various genera) Ehrenbergii Ralfs (Actinocyclus) 522, 523, 526, pi. 23, f. 659 Ehrenbergii Bail, and Herv. (Arachnoidiscus) 507* Ehrenbergii Ktz (Cymbella) 140,* 141, 142, pi. 1, f. 22 Ehrenbergii Ktz. (Diatoma) 350 Ehrenbergii (Ktz.) Gran. (Licmophora) 342, 344, pi. 31, f. 853 var. ovata 344, pi. 31, f. 854 elaborata Grove and Siurt (Kittonia) 479* elegans IV. Sm. { Amphiprora) 265 elegans Heib. (Corinna) 456, 457* elegans Ehr, (Cr.ispedodiscus) 515 elegans Ktz. (Denlicula) 351,* pi. 31, f. 860 var. thermalis 351, pi. 31, f. 861 elegans Grun. (Gomphonema) 268 elegans Witt. (Lepidodiscus) 499* elegans W. Sin. (Navicula) 209, 210, pi. 27, f. 761 elegans (W. Sm.) Gran. ( Plagiotropis) 264, 267,* pi. 6, f. 294 elegans Grev. (Porodiscus) 516* elegans Ehr. (Surirella) 369, 370, pi. 12, f. 576 elliptica (Bieb. ) W. Sm. (Cymatopleura) 367, pi. 12, f. 480^ var. constricta Grun. 367, pi. 12, f. 481^ var. Hibernica 367, pi. 31, f. 863 elliptica A° (Fittstulia) 155 elliptica Ktz. (Navicula) 197, 201, pi. 4, f. 56 (I.) var. ovalis Hilse 201, pi. 4, f. 156 (II.) var. oblongella Naeg. 201, pi. 4, f. 157 var. minima 201, pi. 4, f. 158 elliptica? (Navicula) 163, 197 ellipticus Grev. (Liradiscus) 511* elongatum W. Sm. (Pleurosigma) 250, 253, pi. 6, f. 262 elongatum Ag. (Diatoma) 348, 349, pi. 11, f, 457 var. tenue 349, pi. 11, f. 468 var. hybrida 350, pi. n, f. 469 var. Ehienbeigii 350 emarginatum Ehr. (Biblarium) 358 emarginatus W. Sm. (Tetiacyclus) 358 Emersonia Bail. 1840 (No. 132) Encyonema Ktz. 124, 148, 238 (No. 3) Endosigma Breb. (No. 22) Endostauron Grun. 158 (No. 6) Endyctia Ehr. 429 445 (No. no) enervis Ehr. (Isthmia) 451* 452* pi. 19, f. 625 Entogonia Grev 450, 469, 476 (No. 133) F.ntoloicc Cleve (Naoic'ula) 215 Entomon (Ehr.) Ad. Schm. (Navicula) 191, 195, pi. 26, f. 732. Entomoneis Ehr. (No. 24) Entopyla Ehr. 338, 339, 340, (No. 59) Entopylene 338 Epithelion Pant. 511 (No. 174) Epithemia Breb. 293, 294, 297 (No. 35) Epithemieas 293 Epithemoidea? (Nitzschia) 383 Epsilon var. tenuicomis Grun. (Rutilaria) 433* Ergadensis Greg. (Amphora) 132, 135, pi. 24, f. 683 Ergadensis Gre°. (Pinnularia) 175 erinacea (Peronia) 333* pi. 10, f. 389 Ethmodiscus Caslr. 535 (No. 187) Eu-Anaulus H.V.H. 454 (No. 119) Eubiddulphieae 466 Eucampia Ehr. 450, 461, 462, 464 (No. 127) Eueampieae 461 Euceratoneis Grun. 1865 (No. 33) Eucocconeis Cleve 286, 290 (No. 34) Eucoscinodiscea; 525 Eudoxia A. Schm. (Navicula) 191, 196, pi. 26, f. 739 Eugenia Ad. Schm. (Navicula) 191, 196, pi. 26, f. 740 Eulensteinii Grun. (Pseudo-stictodiscus, 466, 468* Eumeridion Ktz. 1844 (No. 36) Eunotia Ehr. 293, 298, 304, 305 (No. 36) Eunotia Cleve (Amphora) 132, 136, pi. 24, f. 684 Eunotogramma H.V.H. 450, 454 (No. 119) Eunotogramma Weisse 454 (No. 119) Euodia Bailey 450, 510 538 (No, 189) Eupleuria Arnott (No. 6c) Euphyllodium Shad. 365 (No. 75) Eupodisceas 411, 480, 481 (Tribe XXII.) Eupodiscus Ehr, 481, 486, 538 (No. 148) Eusynedra 308, 309 (No. 40) Eutetracyc'us Ralfs. 358 (No. 69) excentrica (Donk.) Grun. (Anorthoneis) 284, 285 excentrica Donk. Cocconeis) 285 excentricus Ehr. (Coscinodiscus) 531, pi. 23, f. 66b Exceutron Ralfs. (No. 166) Exculptum Heib. (Solium) 456* exigua Breb. (Eunotia) 298, 300, pi. 9, f. 369 exigua Lewis (Mastogloia) 153, 155, pi. 2, f. 63 exiguum Ktz. (Gomphonema) 269, 275, pi. 7. f. 317 var. minutissima 275, pi. 7, f. 318 Exilaria Breb. (No. 36) exilis Ktz. (Achnanthes) 278, 281, pi. 8, f. 333 exilis Grun. (Navicula) 216, 217, pi. 4, f. 198 exilissima Grun. (Navicula) 226, 229, pi. 5, f. 234 eximium (Thw.) H.V.H. (Pleurosigma) 250, 259, pi. 7, f. 283 eximium ( Thw.) Colletonema 259 eximius Greg. (Campylodiscus) 379, pi. 32, f. 872 excisa Ad. Schm. {Navicula) 199 Faba (Ehr.) Grun, (Eunotia) 298, 301, pi. 9, f. 374 Falaisensir. Grun. (Navicula) 226, 228, pi. 5, f. 232 Falcatella Rabh. 234 (No. 7) falcatum Donkin {Pleurosigma) 260 falcatum (Donk.) Grun. (Rhoicosigma) 260, pi. 28, f. 801 famelica Ktz. (Synedra) 308, 313, pi. 10, f. 428 fasciata {Lai;.) CI. {Caloneis) 220 fasciculata Grun. (Nitzschia) 396, 397, pi. 16, f. 536 fasciculata Ktz. (Synedra) 314 Fasciculati (Coscinodiscus) 526 fasciculatus A.S. (Coscinodiscus) 533 Fasciola W. Sm. (Pleurosigma) 250, 258, pi. 7, f. 281 var. arcuatum 259 var. prolongatum 259 fastuosa Ehr. (Surirella) 369, 372, 378, pi. 13, f. 583 var. lata 372, pi. 13, f. 584. Favus (Ehr.) H.V.H. (Biddulphia) 468,* 470, 475, pi. 21, f. 643 Favus Ehr (Triceratium) 466, 468,* 475 fenestrata (Lyng.) Ktz. (Tabellaiia) 356,* pi. n, f. 477 Fenestrella Grev. 481, 485, (No. 146) Fibula Breb. (Gomphonema) 333 filiformis W. Sm. (Homceocladia) 406 filiforntis (W. Sm.) H.V.H. (Nitzschia) 406, pi. 33, f. 882 firma W, Sm. (Navicula) 220 flabellata (Carm ) Ag. (Licmophora) 34-!, pi. 31, f. 852 flabellatus (Breb.) Grev. (Asteromphalus) 504 rlaccida (Castr. ) H, Per. Guinardia 417 flexellum Breb. (Achnanthidiuni) 276,* 277, pi. 8, f. 322 flexuosa Ktz. (Eunotia) 299, 304, pi 9, f. 387 var. bicapitata Grun. 304, pi. 9, f. 388 flexuosa Ehr. (Surirella) 374 hocculosa (Roth.) Ktz. (Tabellaria) 356, 357, pi, n, f. 478 floreatus Gr. and St. (Anthodiscus) 498* Flolowii Grun. (Navicula) 226, 230, 234, pi. 5, f. 238 forcipata Grev. vNavicula) 202, 203, pi. 4, f. 163 formosa CI. (Amphora) 136 formosa Greg. (Navicula) 217, 218, pi. 5, f. 199 j formosa CI. (Caloneis) 218 var. Holmeinsis Cl. 218 548 INDEX. Formosa? (Navicula) 164, 217, 234 formosum W. Sm. (Pleurosigma) 250, 254, pi. 6, f. 268 follis Ehr. (Navicula) 216, 217, pi. 27, f. 771 fontinalis Grun. (Navicula) 219, 220, pi. 5, f. 211 fortis Greg- (Navicula) £76,184, pi. 25, f. 715 for lis Greg. (Pinnularia) 184 formosa Hassall (Asterionella) 321, pi. 11, f. 439 var. gracillima (Hantzsch) Grun. 320,* 321, pi. 11, f. 440 var. inflata 321, pi. 11, f. 441 var. Bleakeleyi 321, pi. 30, f. 838 var. Ralfsii 321 Fragilaria Lyngbye 322, 323 (No. 44) Fragilarieae 293, 322 Fragilariineae 293 fragilis Grew (Berkeleya) 245* fraudulenta Ad. Schm. (Navicula) 210, 212, pi. 27, f. 766 Frauenfeldii Grun. {Climaconeis) 346 Frauenfeldianum Grun. (Climacodium) 462* Frauenfeldii Grun. (Thalassiothrix) 322, pi. 30, f. 839 frigida Ktz. [Denticula) 352 Frits/ 11 lia [Ag.) Cleve 239 Frustulum (Ktz.) Grun. (Nitzschia) 400, 403, pi. 17, f. 564 var. minutula 403, pi. 17, f. 565 var. perpusilla Rab. 403, pi. 17, f 566 var. tenella 403 fulgens (Ktz.) W. Sm. (Synedra) 30^, 316,* 311, pi. 10, f-436 fulva Greg. {Denticula) 336 fulvum (Greg.) Ralfs. (Dimeregramma) 335,* 336, pi. 30, f. 849 fusca Greg. (Navicula) 197, 198, pi. 4, f. 153 var. norvegica CI. 199. pi. 26, f. 741 var. subrectangularis 199, pi. 26, f. 742 var. Gregorii CI. 199, pi. 26, f. 743 var. delicatula Ad. Schm. 199, pi. 26, f. 744 var. tenui punctata CI. 199, pi. 4, f. 153 var. hyperborea 199, pi. 26, f. 745 forma excisa 199, pi. 26, f. 746 fusca Ad Schm. {Navicula) 199 Fusiformes (Navicula) 163, 215 fusiformis Grun. (Navicula) 215, pi. 27, f. 768 var. ostrearia (Gaill) H.V. H 215, pi. 27, f. 769. fusoides Grun. (Navicula) 216 Gallica IV. Sm. [Diadesmis) 229 Gallica (W. Sm.) H. Van Heurck (Navicula) 226, 229, 234, pi. 5, f. 237 Gallionella 439 (No. 109) Gallionii h'.hr. (Synedra) 308, 312, pi. io, f. 424 Garckeana Grun. (Rhorconeis) 238* gastroides Ktz. (Cymb;lla) 141, 146, pi. 1, f. 35 var. minor 146, pi. 1, f. 36 Gastrum (Ehr.) Donk. (Navicula) 176, 186, 187, pi. 3, f. 134 var. Placentula 187, pi. 3, f. 135 geminata Donk. (Druridgea) 448 geminatum (Lyngb), Ag. (Gomphonema) 268,* 269, pi, 29, f. 810 Gemma Ehr. (Surirella) 369, 372, 374, pi. 13, f. 582 gemmata (Grun.) H.V. H. (Grunoviella) 332* qemmata Grun. {Sceptroneis '?) 332 gemmatula Grun. (Navicula) 193 gemmifera forma curta (Raphoneis) 329* gentilis Donk. {Navicula) 165 Genuine (Rhizosolenia) 414 Gephyria W. Arnott 338, 340 (No. 60) Gerstenbergeri Rab. (Cylindrotheca) 409 gibba Ktz. (Epithemia) 294, 296, 298, pi. 9, f. 352 a, b var. parallela Grun. 296, pi. 9, f. 353 var. ventricosa 296, 298, pi. 9, f. 354 gibba Bail. (Euodia) 538* gibba Ktz. (Navicula) 168, 172, pi. 2. f. 88 var. brevistriata 172, pi. 2, f. 89 gibberula Ktz. (Epithemia) 294, 297, pi. 30, f. 825 var. producta Grun. 297, pi. 9, f. 361 gibberula Ktz. {Naviiula) 220 gibberula Grun. (Plagiotropis) 264, 266, pi. 29, f. 806 gigantea Grev. (Kittonia) 479 Girodella Gaillon. 1825 (No. 7) globiceps Greg. (Navicula) 168, 173, pi. 2, f. 94 Glceodictyon Ag., 1830 (No. 7) Glceonema Ag., [830 (No. 2) Gloionema Ehr., 1835 (No. 7) Glyphodesmis Grev. 334, 335 (No. 55) Glyphodiscus Grev. 481, 485 (No. 145) Gomphogramma A. Br. 357 (No. 69) Gomphoneis Cleve 268 (No. 27) Gomphonella Rab., 1853 (No. 27) Gomphonema Ag. 243, 268, 333, 347 (No. 27) Gomphonemere 124, 268 (Tribe III.) Gomphonitzschia Grun. 408 (No. 82) Goniothecium Ehr. 412, 428 (No. 95) Gossleriella Schiitt 509, 513 (No. 176) gracile Eul. (Desmogonium) 304 gracile Rabh. (Encyonema) 149, 151, pi. 28, f. 791 bis b var. Scotica 151, pi. 28, f. 791 bis a gracile Ehr. (Gomphonema) 269, 272, pi, 7, f. 309 var. dichotomum 273, pi. 7, f. 310 var. anritum 273, pi. 7, f. 311 gracilis E. {Amphora) 127 gracilis Breb. { Ceratoneis) 409 gracilis (Breb.) Grun. (Cylindrotheca) 409,* pi. 17, f. 574 gracilis (Ehr.) Rab. (Eunotia) 298,* 300, pi. 9, f. 368 gracilis (Ehr.) Grun. (Licm phora) 342, 343, pi. 31, f. 851 gracilis Ktz. (Navicula) 175. 179, pi. 3, f. 109 var. schizonemoides H.V. H, 179, pi. 3, f. no gracilis IV. Sm. {Po losphcnia) 345 gracilis Ehr. (Stauroneis) 158, 159, pi. 25, f. 702 gracilis IV. Sm. {Stauroneis) 159 Grallatoria Ktz., 1844 (No. 40) Grammatophora Ehr. 332, 353 (No. 67) Grammonema Ag., 1832 (No. 44) Grammatonema Ktz., 1844 (No. 44) granulata Roper. (Biddulphia) 470, 473, pi. 20, f. 637 granulata Roper. (Denticella) 466,467* granulata Ktz. {Epithemi 1) 295 granulata (Ehr.) Ralfs. (Melosira) 440, 444, pi. 19, f. 621 var. curvataGrun. 444, pi. 19, f. 622 granulata Bail, nee Bi\'b. {Navicula) 2.\i granulata BrtJb. (Navicula) 210, 211, pi. 4, f. 183 var. maculosa 211, pi. 27, f. 767 Graya Brun. and Grove 450, 458 (No, 123) gregaria Donk. (Navicula) 175, 181, pi. 3, f. 125 Gregoriana Donk. (Toxonidea) 247, pi. 28, f. 792 Gregorianum Grev. (Plagiogranuna) 337,* 338, pi. 10, f. 390 Gregorii Ralfs. (Stauroneis) 158, 160, pi. 1, f. 52 Grevilleana Greg. (Amphora) 131, pi. 24 f. 676 Grevillei Wall. var. Adriatica Grun. (Asterolampra) 504* Grevillei ( W. Sm.) Grun. (Campyloneis) 285,* pi. 8, f. 344 var. Argus Grun. 285, pi. 8, f. 345 Grevillei IV. Sm. Cocconeis 285 Grevillei W. Sm. (Mastogloia) 153, 155, pi. 2, f. 63 Grevillei Agardh. (Navicula) 231, 232, 234, 235, pi. 5, f. 243 Grevillei Agardh. {Schizonema) 231, 232. 234, 235 Grovea Ad. Schm. 450, 480 (No. 140) Grundleri (Navicula) 194 Grunoviella H.V. H, 328, 332, 333 (No. 52) Grunowia (Nitzschia) 383, 390 (No, 81) Grymia Bail. (No. 90) Guinardia H. Per. 412, 417 (No. 86) Gutwinskiella De Toni, 1894 (No. 182) Guyanense Ehr, (Desmogoniam) 305 Guyanensis Grun. (Actinella) 306 Gyrodiscus Witt. 500, 5:3 (No. 165) Gyroptychus Ad. Schm. 495, 500, 501 (No. 163/') Gyrosigma Hassall 249 (No. 22) Halamphora (Amphora) 126, 132 (No. 1) Halionyx Ehr. 496 (No. 157) hamata Rab. {Nitzvhiella) 406 hamata W. Sm. (Synedra) 406 Hantzschia Grunow 380, 392 (No. 80) Hantzschianus Grun. (Stephanodiscus) 520 Hantzschiana Grun. { Trybionella) 385 Hardmaniana Grev. (Palmeria) 539* Hardmarmianus Grun. (Auliscus) 540 Harrisonii (W. Sm.) Grun. (Fragilaria) 323, 326, pi. it, f. 453 Hauckii Grun. (Hemiaulus) 457 Haynaldia Pant 535 (No. 187) Haynaldiella Pant. 535, 536* (No. 187) Hebes Ralfs. (Navicula) 223, 225, pi. 27, f. 776 Heibergia Grev. 476 (No. 133) Heibergii Cleve. (Hemiaulus) 457 Heliopelta Ehr. 496 (No. 1:57) Heliopelta Grun. (Actinoptychus) 494, 496 Heliopelteae 411, 493 (Tribe XXIII.) Helminthopsis H.V.H. 450, 453 (No. 120) Helvitica Ktz. (Cymbella) 141, 148, pi. 1, f. 43 Hemiaulidas 452 (Biddulphiea;) Hemiaulus (Ehr.) H.L. Sm. 450, 455, 457 (No. 121) Hemicyclus (Ehr ) Grun. (Pseudo-Eunolia) 305* Hemidisceae 538 (Coscinodiscea-;) 538 Hemidiscus Wallich 538 (No. 189) hemiptera auct. nee. Ktz. {Navicula) 165 Hemiptychus Ehr., 1848 (No 171) INDEX. 549 Henneclyana Greg. (Synedra) 309, 317,* pi. 10, f. 438 Hennedyere (Navicula) 163, 203 Hennedyi \Y Sm. (Navicula) 203, 204, 205, pi. 4, f. 160 var. clavata 204 var. nebulosa 204, pi. 27, f. 755 Henseniella Schiitt. 416 (No. 84) Hercotheca Ehr. 412, 427 (No. 94) Herculanum Ehr. (Goniphonema) 268 Heribaudia Perag. 542 (No. 191) Heterocampa Ehr. 304 (No. 36) Heterodictvon Grev. 509, ^14 (NTo. 178) Heterompliala Ehr., 1858 (No. 38) Heteroneis CI. 286, 289 (No. 34) Heterostaphania Ehr., 1851 (No. 155) Hibernica IF. Sm. Cymalop .-*. PLATE V. Fig. 199. Navicula forniosa, Greg., p. 218. Fig. 200. Navicula latiuscula, Kutz, p. 218. Fig. 201. Navicula Liburnica, Grun., p. 218. Fig. 202. Navicula permagna, Bailey, p. 218. Fig. 203. Navicula amphisbsena, Bory, p. 219. Fig. 204. Navicula arnphisbasna, var. subsalina, p. 21Q. Fig. 205. Navicula amphisbaena, forma major, p. 219. Fig. 206. Navicula amphisbaena, var. Fenzlii, p. 219. Fig. 207. Navicula limosa, Kutz, p. 219. Fig. 208. Navicula limosa, var. gibberula, p. 220. Fig. 209. Navicula ventricosa (Ehr.?), Donk., p. 220. Fig. 210. Navicula ventricosa, var. minuta, p. 220. Fig. 211. Navicula fontinalis, Grun., p. 220. Fig. 212. Navicula Iridis, Ehr., p. 220. Fig. 213. Navicula Iridis, var. amphigomphus, p. 221. Fig. 214. Navicula Iridis, var. amphirhynchus, p. 221. Fig. 215. Navicula Iridis, var. dubia, p. 221. Fig. 216. Navicula Iridis, var. undulata, p. 221. Fig. 217. Navicula Iridis, var. affinis, p. 221. Fig. 218. Navicula Iridis, var. producta, p. 221. Fig. 219. Navicula Liber, Wm. Sm., p. 222. Fig. 220. Navicula Liber, var. linearis, p. 222. Fig. 221. Navicula Americana, Ehr., p. 223. Fig. 222. Navicula Bacillum, Ehr., p. 224. Fig. 223. Navicula Bacillum, forma minor, p. 224. Fig. 224. Navicula pseudo-Bacillum, Grun., p. 224. Fig. 225. Navicula subhamulata, Grun., p. 224. Fig. 226. Navicula Pupula, Kutz, p. 225. Fig. 227. Navicula incerta, Grun., p. 226. Fig. 228. Navicula Seminulum, Grun., p. 227. Fig. 229. Navicula minima, Grun., p. 227. Fig. 230. Navicula atomoides, Grun., p. 227. Fig. 231. Navicula Atomus, Na?g., p. 227. Fig. 232. Navicula Falaisensis, Grun., p. 228. Fig. 233. Navicula Bulnheimii, Grun., p. 228. Fig. 234. Navicula exilissima, Grun., p. 229. Fig. 235. Navicula binodis (Ehr.), Wm. Mm., p. 229. Fig. 236. Navicula lepidula, Grun., p. 229. Fig. 237. Navicula Gallica (Wm. Sm.), H.Y.H., p. 229. Fig. 238. Navicula Flotowii, Grun., p. 230. Fig. 239. Navicula contenta, Grun., p. 230. Fig. 240. Navicula contenta, var. biceps, p. 230. Fig. 241. Sehizonema Smithii, Ag., p. 231. Fig. 242. Sehizonema cruciferum, Wm. Sm., p. 232. Fig. 243. Sehizonema Grevillei, Ag., p. 232. Fig. 244. Sehizonema ramosissirnum, Ag., p. 232. Fig. 245. Sehizonema ramosissirnum, var. setaceum, p. 233. Fig. 246. Oolletoncma lacustre (Ag.), H.V.H., p. 239. Fig. 247. Scoliopleura latestriata (Breb.), Grun., p. 246. Fig. 248. Scoliopleura tumida (Breb.), Rab., p. 246. Fig. 249. Van Heurckia, rhomboides, Breb., p. 240. Fig. 250. Van Heurckia, rhomboides, var. crassinervis, p. 240. Fig. 251. Van Heurckia, viridula, Breb., p. 240. Fig. 252. Van Heurckia, vulgaris (Thw.), H.V.H., p. 240. Fig. 253. Amphipleura pellucida, Kutz, p. 242. Fig. 254. Berkeleva micans (Lyng.), H.V.H., p. 245. Fig. 255. Berkeleya Dillwynii (Ag.), H.V.H., p. 245. Fig. 256. Toxonidea insignia, Donk., p. 247. Fig. 286- Donkinia recta (Donk.), Grun., p. 248. Fig. 287. Amphiprora (Orthotropis), lepidoptera (Greg.), CI., p. 263. Fig. 288. Amphiprora (Orthotropis), maxima, Greg., p. 264. Fig. 289. Amphiprora alata, Kutz, p. 262. Fig. 290. Amphiprora paludosa, Wm. Sm., p. 262. Fig. 291. Amphiprora hyalina (A. paludosa, var. ?). Fig. 292. Amphiprora paludosa, var. duplex, p. 262. Fig. 293. Amphiprora ornata, Bail, p. 262. __' . -ff{'lu/i/<'' S.lrfyt./ut/ PLATE VI. Fig. 257. Pleurosigma angulatum, Wm. Sm., p. 251. Fig. 258. Pleurosigma angulatum, var. jEstuarii, p. 251. Fig. 25S. Pleurosigma angulatum, var. quadratum, p. 251. Fig. 260. Pleurosigma angulatum, var. major, p. 251. Fig. 261. Pleurosigma angulatum, var. strigosum, p. 251. Fig. 262. Pleurosigma elongatum, "Wm. Sm., p. 253. Fig. 263. Pleurosigma affine, Grun., p. 252. Fig. 264. Pleurosigma affine, var. Nicobarica, p. 252. Fig. 265. Pleurosigma rigidum, Wm. Sm., p. 251. Fig. 266. Pleurosigma naviculaceum, Breb., p. 252. Fig. 267. Pleurosigma intermedium, Wm. Sm., p. 253. Fig. 268. Pleurosigma formosum, Wm. Sm., p. 254. Fig. 269. Pleurosigma decorum, Wm. Sm., p. 254. Fig. 294. Plagiotropis elegans (Wm. Sm.), Grun., p. 265. Fig. 295. Plagiotropis Van Heurckii, Grun., p. 265. ^^^^nu/'a-fyc^^^t^^ta^i^i/^i^^f/y^u^y .&f.&. PLATE VII. Fig. 270. Pleurosigma Hippocampus, Win. Sm., p. 255. Fig. 271. Pleurosigma attenuatum, Wm. Sm., p. 255. Fig. 272. Pleurosigma Balticum, Wm. Sm., p. 255. Fig. 273. Pleurosigma Balticum, var. Brebissonii, p. 256. Fig. 274. Pleurosigma acuminatum (Kiitz), Grun., p. 256. Fig. 275. Pleurosigma strigilis, Wm. Sm., p. 256. Fig. 276. Pleurosigma Spencerii, Wm. Sm., var. Smithii, p. 257. Fig. 277. Pleurosigma Spencerii, var Kiitzingii, p. 257. Fig. 278. Pleurosigma Spencerii, var. nodifera, p. 257. Fig. 279. Pleurosigma Spencerii, var. curvula, p. 258. Fig. 280. Pleurosigmai Parkeri, Harrison, p. 258. Fig. 281. Pleurosigma Fasciola, Wm. Sm., p. 258. Fig. 282. Pleurosigma macrum, Wm. Sm., p., 259. Fig. 283. Pleurosigma eximium (Thw\), H.V.H., p. 259. Fig. 284. Pleurosigma scalproides, Bab., p. 259. Fig. 285. Pleurosigma attenuatum, var. scalprum, p. 255. Fig. 296. Gomphonema constrictum, Ehr., p. 2?0. Fig. 297. Gomphonema constrictum, var. capitatum, p. 270. Fig. 298. Gomphonema constrictum, var. curta, p. 270. Fig. 299. Gomphonema acuminatum, Ehr., p. 270. Fig. 300. Gomphonema acuminatum, var. coronatum, p. 271. Fig. 301. Gomphonema Augur, Ehr., p. 271. Fig. 302. Gomphonema Augur, var. Gautieri, H.V.H., p. 271. Fig. 303. Gomphonema montanum, Schumann, p. 271. Fig. 304. Gomphonema montanum, var. subclavatum, p. 272. Fig. 305. Gomphonema montanum, var. commutatum, p. 272. Fig. 306. Gomphonema parvulum, Kiitz, p. 272. Fig. 307. Gomphonema parvulum, var. lanceolata, p. 272. Fig. 308. Gomphonema parvulum, var. subcapitata, p. 272. Fig. 309. Gomphonema gracile, Ehr., p. 272. Fig. 310. Gomphonema gracile, var. dichotomum, p. 273. Fig. 311. Gomphonema gracile, var. auritum, p. 273. Fig. 312. Gomphonema micropus, Kiitz, p. 273. Fig. 313. Gomphonema intricatum, Kiitz, p. 273. Fig. 314. Gomphonema angustatum, Kiitz, p. 273. Fig. 315. Gomphonema olivaceum, Kiitz, p. 274. Fig. 316. Gomphonema olivaceum, var. vulgaris, p. 275. Fig. 317. Gomphonema exiguum, Kiitz, p. 275.^ Fig. 318. Gomphonema exiguum, var. minutissima, p. 275. Fig. 319. Bhoicosphenia curvata (Kiitz), Grun., p. 275. Fig. 320. Bhoicosphenia curvata, var. marinum, p. 276. Fig. 321. Bhoicosphenia Van Heurckii, Grun., p. 276. __ . .' /f?/!,u^aw&u*&& /rf/Ml* ^Sr in 524 342 345 J MALVAUX- 344 Fig . 346. Fig . 347. Fig, , 348. Fig. 349. Fig. 350. Fig. 351. Fig. 352. Fig. 353. Fig. 354. Fig. 355. Fig. 356. Fig. 357. Fig. 358. Fig. 359. Fig. 360. Fig. 361. Fig. 362. Fig. 363. Fig. 364. Fig. 365. Fig. 366. Fig. 367. Fig. 363. Fig. 369. Fig. 370. Fig. 371. Fig. 372. Fig. 373. Fig. 374. Fig. 375. Fig. 376. Fig. 377. Fig. 378. Fig. 379. Fig. 380. Fig. 381. Fig. 382. Fig. 383. Fig. 384. Fig. 385. Fig. 386. Fig. 387. Fig. 388. PLATE IX. Epithemia turgida (Ehr.), Kiitz, p. 294. Epithemia turgida, var. Westermanni, p. 295. Epithemia turgida, var. gramilata, p. 295. Epithemia turgida, var. Yertagus, p. 2P5. Epithemia Hyudmanni, Wm. Sm., p. 295. Epithemia Sorex, Kiitz, p. 295. ' Epithemia gibba, Kiitz, p. 296. Epithemia gibba, var. parallela, p. 296. Epithemia gibba, var. ventricosa, p. 296. Epithemia Argus, Kiitz, p. 296. Epithemia Argus, var. amphicephala, p. 2S6. Epithemia Zebra (Ehr.), Kiitz, p. 296. Epithemia Zebra, var. proboscidea, p. 297. Epithemia Musculus, Kiitz, p. 297. Epithemia Musculus, var. constricta, p. 297. Epithemia gibberula, var. producta, p. 297. Eunotia Areus, Ehr., p. 299. Eunotia Arcus, var. minor, p. 299. Eunotia. Arcus, var. uncinata, p. 299. Eunotia Arcus, var. bidens, p. 299. Eunotia major (Wm. Sm.), Rab., p. 300. Eunotia major, var. bidens, p. 300. Eunotia gracilis, (Ehr.), Rab., p. 300. Eunotia exigua. Breb., p. 300. Eunotia pectinalis (Kiitz,), Rab., forma curta, p. 301. Eunotia pectinalis, forma elongata, p. 301. Eunotia pectinalis. var. ventricosa, p. 301. Eunotia pectinalis, var. undulata, p. 301. Eunotia Faba (Ehr.), Grun., p. 301. Eunotia tridentula, Ehr., p. 301. Eunotia praerupta, Ehr., p. 302. Eunotia praerupta, forma curta, p. 302. Eunotia praerupta, var. inflata, p. 302. Eunotia praerupta, var. bidens, p. 302 Eunotia praerupta, var. bigibba, p. 302. Eunotia robusta, Ralfs., p. 303. Eunotia robusta, var. tetraodon, p. 303. Eunotia triodon, Ehr., p. 303. Eunotia lunaris (Ehr.), Grun., p. 303. Eunotia lunaris, var. subarcuata, p. 304. Eunotia lunaris, var. bilunaris, p. 304. Eunotia flexuosa, Kiitz, p. 304. Eunotia flexucsa, var. bicapitata, p. 304. __/ ' '/{'tut/*'/. "flMel6&2&!ul&metsJedst maze, ?T &f.j. 376 377 PLATE X. Fig. 389. Peronia erinacea, Breb. and Am., p. 333. *ig. 390. Plagiogramma Gregorianum, Grev., p. 338. tig. 391. Plagiogramma Van Heurckii, Grun., p. 338. v1"' ,n, tinier egramma minor (Greg.), Ralfs., p. 336. *ig. 393. Dimeregramma minor, var. nana, p. 336. tig. 394-. Raphoneis amphiceros, Ehr., p. 330. Fig. 395 Raphoneis amphiceros, var. rhombica, p. 330. *ig. 396. Raphoneis Belgiea, Grun., p. 330. Fig. 397. Raphoneis Surirella (Ehr.?), Grun., p. 330. Fig. 398. Raphoneis Surirella, var. Australis, p. 330. Fig. 399. Sceptroneis Caduceus, Ehr., p. 332. Fig. 400. Raphoneis Liburnica. Grun.. p. 331. Fig. 401. Ceratoneis Arcus, Kiitz, p. 306. Fig. 402. Synedra pulehella, Kiitz, p. 309. Fig. 403. Synedra pulehella, forma major, p. 309. Fig. 404. Synedra pulehella, var. Smithii, p. 309. Fig. 405. Synedra pulehella, var. laneeolata, p. 309. Fig. 406. Synedra Vaucheriae, Kiitz, p. 310. Fig. 407. Synedra Vaucherin?, var. parvula, p. 310. Fig. 408. Synedra Vaueheris, var. perminuta, p. 310. Fig. 409. Synedra Tina (Nitzsch), Ehr., p. 310. Fig. 410. Synedra Ulna, var. splendens, p. 310. Fig. 411. Synedra Ulna, var. subiequalis, p. 310. Fig. 412. Synedra Ulna, var. longissima, p. 310. Fig. 413. Synedra Ulna, var. spathulifera, p. 311. Fig. 414. Synedra Ulna, var. amphirhvnehus, p. 311. Fig. 415. Synedra Ulna, var. Danica, 'p. 311. Fig. 416. Synedra Ulna, var. laneeolata, p. 311. Fig. 417. Synedra Ulna, var. obtusa, p. 311. Fig. 418. Synedra Ulna, var. oxyrhynchus, p. 311. Fig. 419. Synedra Ulna var. vitrea, p. 311. Fig. 420. Synedra Acus (Kiitz), Grun.. p. 311. Fig. 421. Synedra Acus, var. delicatissima, p. 312. Fig. 422. Synedra Acus, var. angustissima, p. 312. Fig. 423. Synedra radians (Kiitz), Grun., p. 311. Fig. 424. Synedra Gallionii, Ehr., p. 312. Fig. 425. Synedra investiens, Wm. Sm., p. 313. Fig. 426. Synedra barbatula, Kiitz, p. 313. Fig. 427. Synedra capitata, Ehr., p. 313. Fig. 428. Synedra famelica, Kiitz, p. 313. Fig. 429. Synedra amphieephala, Kiitz, p. 313. Fig. 430. Synedra afhnis, Kiitz, p. 314. Fig. 431. Synedra affinis, var. tabulata, p. 314. Fig. 432. Synedra affinis, var. parva, p. 314. Fig. 433. Synedra affinis, var. fasciculata, p. 314. Fig. 434. Synedra nitzschioides, Grun., p. 314. Fig. 435 Synedra crystallina (Lyng.), Kiitz, p. 315. Fig. 436. Synedra fulgens (Kiitz), Wm. Sm., p. 316. Fig. 437. Synedra undulata (Bailey), Greg., p. 317. Fig. 438. Synedra Hennedyana, Greg., p. 317. J^Z/fontefai z^a^/^Aa^n^^^0f4yu^ JV. PLATE XI. Fig-. 439. Asterionella formosa, Hassall, p. 321. Fig. 440. Asterionella formosa, var. gracillinia, p. 321. Fig. 441. Asterionella formosa, var. inflata, p. 321. Fig. 442. Fragilaria virescen®, Ralfs., p. 323. Fig. 443. Fragilaria hyalina (Kiitz), Grun., p. 324. Fig. 444. Fragilaria Crotonensis (A. M. Edwards), Kitton, p. 324. Fig. 445. Fragilaria Crotonensis, var. prolongata. p. 325. Fig. 446. Fragilaria capucina, Desmazieres, p. 325. Fig. 447. Fragilaria capucina, var. mesolepta, p. 325. Fig. 448. Fragilaria capucina, var. acuta, p. 525. Fig. 449. Fragilaria capucina, var. acuminata, p. 325. Fig. 450. Fragilaria construens (Ehr.), Grun., p. 325. Fig. 451. Fragilaria construens, var. Venter, p. 325. Fig. 452. Fragilaria construens, var. binodis, p. 326. Fig. 453. Fragilaria Harrisonii (Wm. Sm.), Grun., p. 326. Fig. 454. Fragilaria mutabilis (Wm. Sm.), Grun., p. 326. Fig. 455 Fragilaria brevistriata, Grun., p. 326. Fig. 456. Cymatosira Belgiea, Grun., p. 327. Fig. 457. Campylosira cymbelliformia (A.S.), Grun., p. 357. Fig. 458. Licmophora Anglica (Kiitz), Grun., p. 343. Fig. 459. Licmophora Dalmatica (Kiitz), Grun., p. 343. Fig. 460. Licmophora Lyngbyei (Kiitz), Grun., p. 344. Fig. 461. Denticula tenuis, Kiitz, p. 352. Fig. 462. Denticula tenuis, var. inflata, p. 352. Fig. 463. Denticula tenuis, var. frigida, p. 352. Fig. 464. Denticula subtilis, Grun., p. 352. Fig. 465. Diatoma vulgare. Bory, p. 348. Fig. 466. Diatoma vulgare, var. linearis, p. 349. Fig. 467. Diatoma elongatum, Ag., p. 349. Fig. 468. Diatoma elongatum, var. tenue, p. 349. Fjg. 469. Diatoma elongatum, var. hybrida, p. 350. Fig. 470. Diatoma hiemale (Lyngb.)," Heib., p. 350. Fig. 471. Diatoma hiemale, var. mesodon, p. 350. Fig. 472. Diatoma anceps (Ehr.), Grun., p. 350. Fig. 473. Diatoma anceps, var. anomalum, p. 350. Fig. 474. Meridion circulare, Ag., p. 347. Fig. 475. Meridion circulare, var. constrictum, p. 348. Fig. 476. Meridion circulare, var. Zinkenii. p. 348. Fig. 477. Tabellaria fenestrata (Lyngb.), Kiitz, p. 356. Fig. 478. Tabellaria floeeulosa (Roth.), Kiitz, p. 357. Fig 479. Grammatophora marina (Lyngb.), Kiitz, p. 354. Fig. 483a. Grammatophora marina, \ar. macilenta, p. 354. Fig. 481a. Grammatophora angulosa, Ehr., p. 355. Fig. 482a. Grammatophora serpentina (Ralfs.), Ehr., p. 355. Fig. 489a. Tetracyclus rupestris (A. Braun), Grun., p. 357. Jz^S?^fc*As /^u>i^MM^^ca^ru^JtiiiM^/iafi/^' &f.*I. PLATE XII. Fig. 483:.. Striatella delicatula (Kiitz), Grun., p. 363. Fig. 484a. .Striatella irttrrupta (Ehr.), Heiberg., p. 363. Fig. 485a, Striatella unipunctata, Ag., p. 363." Fig. 486a. Rhalxlonema Adriaticum, Kiitz, p. 360. Fig. 487a. Rhabdonenia arcuatum (Ag.), Kiitz, p. 360. Fig. 488a. Rhalxlonema minutum, Kiitz, p. 361. Fig. 483b. Cymatopleura elliptica (Rreb.), Win. Sm., p. 367. Fig. 481b. Cymatopleura elliptica, var. constrieta, p. 367. Fig. 482b. Cymatopleura Solea (Rreb.), Wm. Sm., p. 367. Fig. 575. Surirella biseriata, Breb., p. 369. Fig. 576. Surirella elegans, Ehr., p. 370. Fig. 577. Surirella robusta, Ehr., p. 371. Fig. 578. Surirella robusta, var. splendida, p. 371. Fig. 579. Surirella robusta, var. tenera, p. 371. J M*LV*VA. PHDTQ7YP ■ PLATE X11I. Fig. 580. Surirella striatula, Turpin, p. 371. Fig. 581. .Surirella striatula, var. biplicata, p. 371. Fig. 582. Surirella Gemma, Ehr., p. 372. Fig. 583. Surirella fastuosa, Ehr., p. 372. Fig. 584. Surirella fastuosa, var. lata, p. 372. Fig. 585. Surirella cvalis, Breb., p. 373. Fig. 586. Surirella ovalis, var. Crumena, p. 373. Fig. 587. Surirella ovalis, var. ovata, p. 373. Fig. 588. Surirella ovalis, var. minuta, p. 373. Fig. 589. Surirella ovalis, var. salina, p. 373. Fig. 590. Surirella ovalis, var. angusta, p. 373. Fig. 591. Surirella ovalis, var. pinnata, p. 373. Fig. 592. Surirella spiralis, Kiitz, p. 374. PLATE XIV. Fig. 593. Oampylodiscus Hibernicus, Ehr., p. 379. Fig. 594. Oampylodiscus Hibernicus, var. Noricus, p. 379. Fig. 595. Oampylodiscus Thuretii, Breb., p. 378. Fig. 596. Oampylodiscus decorus, Breb., p. 376. Fig. 597. Oampylodiscus decorus, forma minima, p. 376. Fig. 598. Oampylodiscus Olypeus, Ehr., p. 377. Fig. 599. Oampylodiscus bicostatus, Win. Sm., p. 379. Fig. 600. Oampylodiscus Echeneis, Ehr., p. 377. £%?S4. ._/ r*faiy4rji( PHCr?TYP PLATE XV. Tig. 438b. Hantzsohia amphioxys (Ehr.), Grun., p. 381. Fig. 484b. Hantzsohia amphioxys, var. major, p. 381. Fig. 485b. Hantzsohia amphioxys, var. intermedia, p. 381. Fig. 486b. Hantzsohia, amphioxys, var. vivax, p. 381. Fig. 487b. Hantzschia amphioxys, var. elongata, p. 381. Fig. 488b. Hantzsohia virgata (Roper), Grim., p. 381. Fig. 489b. Hantzsohia marina (Donkin), Grun., p.382. Fig. 490. Nitzschia navieularis (Breb.j, Grun., p. 384. Fig. 491. Nitzschia punctata (Win. Sm.), Grun., p. 384. Fig. 492. Nitzschia punctata, var. elongata, p. 385. Fig. 493. Nitzschia Tryblionella, Hantzsch., p. 385. Fig. 494. Nitzschia Tryblionella, var. Levidensis, p. 385. Fig. 495. Nitzschia Tryblionella, var. calida, p. 385. Fig. 496. Nitzschia Trvblionella, var. littoralis, p. 385. Fig. 497. Nitzschia debilis (Arnott), Grun., p. 385. Fig. 498. Nitzschia angustata (Wm. Sm.), Grun., p. 385. Fig. 499. Nitzschia angustata, var. curta, p. 386. Fig. 500. Nitzschia panduriformis Grun., p. 386. Fig. 501. Nitzschia eonstricta (Greg.), Gran., p. 386. Fig. 502. Nitzschia eonstricta, forma parva, p. 386. Fig. 503. Nitzschia plana, Wm. Sm., p. 387. Fig. 504. Nitzschia Hungarica, Grun., p. 387. Fig. 505. Nitzschia apkulata (Greg.), Grun.. p. 387. Fig. 506. Nitzschia acuminata (Wm. Sm.), Grun., p. 388. Fig. 507. Nitzschia eireumsuta (Bail.), Grun., p. 388. Fig. 508. Nitzschia dubia, Wm. Sm., p. 389. Fig. 509. Nitzschia thermalis (Kiitz), Grun., p. 389. Fig. 510. Nitzschia thermalis, var. intermedia, p. 389. Fig. 511. Nitzschia eommutata, Grun., p. 389. Fig. 512. Nitzschia bilobata, Wm. Sm., p. 389. Fig. 513. Nitzschia bilobata, var. minor, p. 390. Fig. 514. Nitzschia Denticula, Grun., p. 390. Fig. 515. Nitzschia Denticula, var. Delognei, p. 390. Fig. 516. Nitzschia sinuata (Wm. Sm.). Grun., p. 390. Fig. 517. Nitzschia sinuata, var. Tabellaria, p. 391. -L/. "-'/' • .v /.//.' /C<,;.*,1j,,//.'-//u'. ',/. , Ve&tp &¥ *s. PLATE XVI. Fig. 518. Fig. 519. Fig. 520. Fig. 521. Fig. 522. Fig. 523. Fig. 524. Fig. 525. Fig. 526. Fig. 527. Fig. 528. Fig. 529. Fig. 530. Fig. 531. Fig. 532. Fig. 533. Fl£\ 534. Fig. 535. Fig. 536. Fig. 537. Fig. 538. Fig. 539. Fig. 540. Fig. 541. Fig. 542. Fig. 343. Fig. 544. Fig. 545. Fig. 546. Fig. 547. Nitzschia paradoxa (Gmel.), Grun., p. 392. Nitzschia paradoxa, var. major, p. 392. Nitzschia Petitiana, Grun., p. 393. Nitzschia angularis, Win. Sm., p. 393. Nitzschia angularis, var. affinis, p. 393. Nitzschia spathulata, Breb., p. 393. Nitzschia spathulata, var. hyalina, p. 394. Nitzschia dissipata (Kiitz), Grun., p. 394. Nitzschia, dissipata, var. media, p. 395. Nitzschia dissipata, var. acuta, p. 395. Nitzschia sigmoidea (Ehr.), Wm. Sm., p. 395. Nitzschia vermicularis (Kiitz), Grun., p. 395. Nitzschia Brebissonii, Win. Sm., p. 396. Nitzschia sigma, Wm. Sm., p. 396. Nitzschia sigma, var. intercedens, p. 396. Nitzschia sigma, var. rigida, p. 396. Nitzschia sigma, var. rigidula, p. 396. Nitzschia sigma, var. Sigmatella, p. 397. Nitzschia fasciculata, Grun., p. 397. Nitzschia obtusa, Wm. Sm., p. 397. Nitzschia obtusa, var. soalpelliformis, p. 397. Nitzschia obtusa, var. nana, p. 398. Nitzschia obtusa, var. brevissima, p. 398. Nitzschia spectabilis (Ehr.), Ralfs., p. 398. Nitzschia linearis (Ag. ), Wm. Sm., p. 399. Nitzschia linearis, var. tenuis, p. 399. Nitzschia vitrea, Norman., p. 399. Nitzschia vitrea, forma major, p. 399. Nitzschia vitrea, var. salinarum, p. 399. Nitzschia vitrea, var. recta, p. 400. ^^£^^/^^ui^^Aa^ti^aiy^&^^u^y &S/6- 537 545 544 S46 543 PLATE XVIL Fig. 548. Nitzschia lanceolate,, Win. Sm., p. 400. Fig. 549. Nitzschia lanceolata, forma minor, p. 401. Fig. 550. Nitzschia lanceolata, forma, minima, p. 401. Fig. 551. Nitzschia lanceolata, var. incrustans, p. 401. Fig. 552. Nitzschia subtilis, Grun., p. 401. Fig. 553. Nitzschia subtilis, var. paleacea, p. 401. Fig. 554 Nitzschia Palea (Kiitz), Wm. Sm., p. 401. Fig. 555. Nitzschia Palea, var. debilis, p. 402. Fig. 556. Nitzschia Palea, var. tenuirostris, p. 402. Fig. 557. Nitzschia Palea, var. fonticola, p. 402. Fig. 558. Nitzschia microcephala, Grun., p. 402. Fig. 559. Nitzschia microcephala,, var. elegantula, p. 402. Fig. 560. Nitzschia communis, Rab., p. 402. Fig. 561. Nitzschia communis, var. abbreviata, p. 402. Fig. 562. Nitzschia communis, var. obtusa, p. 402. Fig. 563. Nitzschia amphibia, Grun., p. 403. Fig. 564. Nitzschia Frustulum (Kiitz), Grun., p. 403. Fig. 565. Nitzschia Frustulum, var. minutula, p. 403. Fig. 566. Nitzschia Frustulum, var. perpusilla, p. 403. Fig. 567. Nitzschia Delognei, Grun., p. 403. Fig. 568. Nitzschia longissima (Breb.), Ealfs., p. 404. Fig. 569. Nitzschia longissima, forma parva, p. 404. Fig. 570. Nitzschia longissima, var. Closterium, p. 405. Fig. 571. Nitzschia acicularis, Wm. Sm., p. 405. Fig. 572. Nitzschia Lorenziana, Grun., p. 405. Fig. 573. Nitzschia Lorenziana, var. incurva, p. 406. Fig. 574. Cylindrotheca gracilis (Breb.), Grun., p. 409. Fig. 601. Rhizosolenia styliformis, Brightw., p. 415. Fig. 602. Rhizosolenia setigera, Brightw., p. 414. Fig. 606. Ditylum Brightwellii (West), Grun., p. 424. Fig. 607. Ditylum intricatum (West), Grun., p. 424. -©iS-^K? u^an'^u^u/^ —£cafr?ru' 'di ■^s)i/yiaat/ &e. // 568 PLATE XVIII. Fig. 603. Chaetoceros armatum, West, p. 421. Fig. 604. Cha-toceros Wighamii, Brightw., p. 422. ?-g' ^o' Chaetoceros (Baeteriastrum), varians, Lauder, p. 422 Xig. 608. Melosira nummuloides (Bory), A«. p 440 Fig. 609. Melosira Westii, Wm. Sm., p. 441.' Fig. 610. Melosira Borreri, Grev., p. 441. Fig-. 611. Melosira varians, Ag., p. 441. Fig. 612. Melosira Jurgensii, Ag., p. 442. Fig. 613. Melosira Jurgensii, var. octogona, Grun., p. 442. Sl/%^tm4^fani?Z^t^z£ca^ &S./r. PLATE XIX. iig. 614. Melosira Roeseana, Rab., p. 442. Fig. 615. Melosira Roeseana, var. spiralis, p. 442. Fig. 616. Melosira distars, Kiite, p. 442. Fig. 617. Melosira distans, var. nivalis, p. 443. Fig. 618. Melosira crtnulata, Kiitz, p. 443. Jig. 619. Melosira crenulata, forma tenuis, p. 443. Fig. 620. Melosira crer.ulata, forma Binder'iana, p. 443. .tig. 621. Melosira arer.aria, Moore, p. 443. Fig. 621. Melosira gramilata (E'ir.), Ralfs., p. 444. Fig. 622. Melosira granulata, var. eurvata, p. 444. Fig. 623. Melosira Dickiei (Thwaites), Kiitz, p. 444. Fig. 624. Melosira sulcata, Kiitz, p. 444. Fig. 625. Isthmia enervis, Ehr., p. 451. Fig. 626. Anaulus debilis (Grun.), H.V.H., p. 454. Fig. 627. Lithodesmium undulatum, Ehr., p. 465. Fig. 628. Eucampia Zodiacus, Ehr., p. 461. Fig. 629 Bellerochea Malleus (Brightw.), H.V.H. j 464 -^/ . '^/&fiit ■'/t/fe.SCtMic/.-J- ' /i;£v/u^. j # PLATE XX. Fig. 630. Fig. 631. Fig:. 632. Fig. 633. Fig. 634. Fig. 635. Fig. 636. Fig. 637. Fig. 639. Fig. 640. Biddulphia pulchella. Gray., p. 4-70. Biddulphia aurita (Lyngb.), Breb., p. 471. Biddulphia aurita, var. minima-, p. 472. Biddulphia aurita, var. minuscula, p. 472. Biddulphia Rhombus (Ehr.), Wm. Sm., p. 472. Biddulphia Rhombus, var. trigona, p. 472. Biddulphia Baileyii, Win. Sm., p. 473. Biddulphia granulata, Roper, p. 473. Biddulphia la? vis, Ehr., p. 474. Biddulphia laevis, forma minor, p. 474. @fzk 51ta ■ / . /(csiUi'clWt d&?MU 'i/c ■yJriyr//u{' &?.*< PLATE XXI. Fig. 638. Biddulphia turgida, Win. Sm., p. 473. Fig. 641. Biddulphia Smithii (Ralfs.), H.V.H., p. 474. Fig. 642. Biddulphia antediluviana (Ehr.), H.V.H.. p. 475. Fig. 643. Biddulphia Favus (Ehr.), H.V.I I., p. 475. Fig. 644. Biddulphia alternans (Bail.), H.V.H., p. 475. Fig. 645. Biddulphia sculpta (Shadb.), H.V.H., p. 476. Fig. 646. Auliscus seulptus (Wm. Sm.), Ralfs., p. 482. Fig. 647. Eupodiscus Argus, Ehr., p. 487. r'/s- b//^ ■-'/ . ' ' /ft /<;s /« ->/ y6t/u-/r^.!a/','?s/lL> (/(,_:/],//,_. rr 21. J MALVAUX PLATE XXII. Fig. 64-8. Actinoptychus undulatus (Ehr.), p. 496. Fig. 649. Actinoptychus splendens (Khadb.). Ralfs., p. 497 Fig. 650. Hyalodiscus stelliger, Bail., p. 449. Fig. 651. Cyclotella striata (Kiitz), G-run., p. 446. Fig. 652. Cyclotella antiqua, Wm. Sm., p. 446. Fig. 653. Cyclotella comta (Ehr.), Kiitz, p. 446. Fig. 654 Cyclotella comta, var. radiosa, p. 447. Fig. 655. Cyclotella operoulata., Kiitz, p. 4-47. Fig. 656. Cyclotella Meneghiniana, Kiitz, p. 447. Fig. 657. Cyclotella Kiitzingiana, Chauvin, p. 447. -lJ .' 'Ti-/, ,V /,/;/ sK/t;c/(-^«n'r'??r,,:>'/.-, /i,/y;0\'t'/C76u.£cA — ^U*<&?rz^e4f . &xt. PLATE XXV. Fig. 695. Cymbella amphicephala, var. Anglica, p. 142. Fig. 696. Cymbella laevis, var. rupicola, p. 144. Fig. 697. Cymbella tumidula, C-irun., p. 145. Fig. 698. Cymbella aequalis, Wm. Sm., p. 145. Fig. 699. Cymbella abnormis, Grun., p. 146. Fig. 700. Mastogloia apieulata, Wm. Sm., p. 154. Fig. 701. Mastogloia Closeii,, O'Meara, p. 155. Fig. 702. Stauroneis gracilis, Ehr., p. 159. Fig. 703. Stauroneis obliqua, Greg., p. 161. Fig. 704. Navicula quadratarea, A. 8., pp. 167, 207. Fig. 705. Navicula Alpina, Baits., p. 169. Fig. 706. Navicula divergent, Wm. Sm., p. 170. Fig. 707. Navicula blanda, A.S., p. 175. Fig. 708. Navicula sejuncta, A.S., p. 175. Fig. 709. Navicula claviculus, Greg., p. 174. Fig. 710. Navicula erucifera, Gruu., p. 183. Fig. 711. Navicula nana, Greg., p. 182. Fig. 712. Navicula eanoellata, var. ammophila, p. 183. Fig. 713. Navicula innexa (Greg.), Balfs., p. 184. Fig. 714. Navicula opima, Grun., p. 184. Fig. 715. Navicula fortis, Greg., p. 184. Fig. 716. Navicula longa, Greg., p. 185. Fig. 717. Navicula Solaris, Greg., p. 186. Fig. 718. Navicula Semen, Ehr., p. 187. Fig. 719. Navicula capita ta, Ehr., p. 187. Fig. 720. Navicula apieulata, Breb., p. 188. Fig. 721. Navicula Kiitzingiana, H.L.Sm., p. 188. Fig. 722. Navicula directa, Wm. Sm., p. 189. Fig. 723. Navicula directa, var. subtilis, p. 189. Fig. 724 Navicula superimposita, A.S., p. 189. Fig. 725. Navicula conrpressicauda, A.S., p. 190. Fig. 726. Navicula Northumbrica, Donk., p. 189. Fig. 727. Navicula ina?quilatera, Lag., p. 190. Fig. 728. Navicula Beyrichiana, A.S., p. 192. cw ^W {^€^U:,Z-J^-C PLATE XXXIII. Fig. 877. Nitzschia vivax, Wm. Sm., p. 392. Fig. 873 Nitzschia distans, Greg., p. 394. Fig. 879. Nitzschia cursoria (Donk), Grun., p. 394. Fig. 880. Nitzschia ovalis, Arnott, p. 403. Fio-. 881. Homceoeladia Martiana, Ag., p. 406. Fig. 882. Hoinoeocladia filiformis, Wm. Sm., p. 406. Fig. 883. Rhizosolenia robusta, Norm., p. 414. Fig. 884. Rhizosolenia calcar-avis, Schultze, p. 415. Fig. 885. Rhizosolenia imbricata, Bright., p. 415. Fig. 886. Rhizosolenia imbricata, var. Shrubsoln, p. 415. Fig. 887. Rhizosolenia alata, Bright., p. 416. Fig. 888 Rhizosolenia alata, Bright., p. 416. Fi°. 889. Skeletonema costatum (Grev.), CI., p. 437. Fig. 890. fikeletor.cma costatum (Grev.), CI., p. 437. 877 875 366 A m - % 882 I V 886 985 883 U-J 887 irif«w 890 884 888 PLATE XXXIV. Fig. 891. Isthmia nervosa, Kiitz, p. 452. Fig. 892. Ananhis debilis (Grun.), H.V.H., p. 454. Fig. 893. Eucampia Britannica, Wm. Sm., p. 461. Fig. 894. Biddulphia. Eegina, Wm. Sm., p. 471. Fig. 895. Biddulphia Tuomeyi, Bail., p. 471. Fig. 896. Biddulphia Tuomeyi, Bail., p. 471. Fig. 897. Actinocyclus crassus (Wm. Sm.), Ealfs., p. 524. Fig. 898. Actinocyelus Roperii (Breb.), Kitton, p. 524. Fig. 399. Cosoinodiscus perforates, Ehr., p. 529. Fig. 900. Coscinodiscus nobilis, Grun., p. 530. Fig. 901. Coscinodiscus subtilis (Ehr.?), Grun., p. 532. Fig. 902. Coscinodiscus Gazellae Janisch, p. 534. Fig. 903. Coscinodiscus Kiitzingii, A.S., p. 532. Fig. 904. Coscinodiscus punctulatus, Greg., p. 533. Fig. 905. Coscinodiscus dccipiens, Grun., p. 532. M VZL <^£?ta-zc& - S^&z&Tz&kf . &J4. I?;- - - :;--':s:r 'mm 900 90i PLATE XXXV. Fig. 906. Amphora Pusio, Cleve, p. 128. Fig. 907. Amphora arenicola Grun., p. 128. Fig. 908. Amphora limbata, Cleve and G-run., p. 136. Fig. 909. Campylodiseus angularis, Greg., p. 378. Fig. 910. Navieula Liber, Wm. Sm., var. bicuneata, Grun., p. 222. Fig. 911. Navieula perpusilla, Grun., p. 229. (x 1,000). Fig. 912. Dcnkinia carinata (Donk.), Ralfe., p. 248. Fig. 913a. Raphidodiscus (vel Melonavieula ), Marylandioa, Th., Christian, p. 236. (x 480). Fig. 913b. Raphidodiscus (vel Melonavieula), Christiani Gascoyne, p. 236. (x 1,000). Fig. 914. Pleurosigma aoutum, Norman, p. 254. Fig. 915. Nitzschia (Homasocladia), subcohcerens, Grun., var. Scotica, Giun p. 406. Fig. 916. Cha?toeeros paradoxum, CI., var. Eibenii, Grun., p. 422. Fig. 917. Hvalodiscus subtilis, Bail., forma minor, H.V.H., H. Scotious (Kiitz), Grun., p. 449. £aT ' J$&?vu' Paw a?if£UKc4. _ J£yt