A_:k- ,1 -2i THE GENUS MONTICULIPORA ITS SUB-GENERA BY THE SAME AUTHOR. ON THE STRUCTURE AND AFFINITIES OF THE " Tabulate Corals" of the Palaeozoic Period. With Critical Descriptions of Illustrative Species. Illustrated with Engrav- ings on Wood and 15 Lithographed Plates. Royal 8vo, 2is. "A magnificent octavo volume, which we have no hesitation in pronouncing the best of all the author's numerous works It is impossible to overlook the many signs of the most careful work displayed in this portion of Dr Nicholson's book; and al- though, as we have seen, he is compelled by the very nature of the objects of his study to leave many points in a state of uncertainty, which, indeed, may perhaps never be cleared up, yet in his present volume he has made our knowledge of these puzzling organisms take a great step forward. In the matter of illustrations, also, we are here in a condition of magnificent luxury." — Papular Science Revieii'. "Whatever future discoveries may disclose as to the affinities of these corals, this work will always retain a permanent value for its minute and faithful description of these organic remains, and all students of Palaeontology will be indebted to Professor Nicholson for thus bringing together in a single volume the history of this important division." — Geological Magazine. A Manual of Palaeontology, for the use of stud- ents. With a General Introduction on the Principles of Paleontology. Second Edition, Revised throughout, and greatly enlarged. Illustrated with 722 Engravings. Two Volumes, 8vo, 42s. " The most complete and systematic treatise on the subject in the English language. It has not only been thoroughly revised, and to a great extent rewritten, but so much enlarged by the addition of new matter that it may claim to be considered to all in- tents and purposes a new book." — Saturday Review. " Professor Nicholson has placed all geological and most zoological students under a great obligation by the masterly way in which he has collected, arranged, and clas- sified the facts of the most difficult of modern sciences, palfeontology. No library of natural science can afford to be without the present work." — Science Gossip. WILLIAM BLACKWOOD & SONS, Edinburgh and London. ON THE STRUCTURE AND AFFINITIES OF THE GENUS MONTICULIPORA AND ITS SUB-GENERA CRITICAL DESCRIPTIONS OF ILLUSTRATIVE SPECIES BY H?!j\LLEYNE NICHOLSON M.D., D.Sc, F.R.S.E, F.L.S. PROFESSOR OF NATURAL HISTORY IN THE UNIVERSITY OF ST ANDREWS WILLIAM BLACKWOOD AND SONS EDINBURGH AND LONDON ^' MDCCCLXXXI PREFACE. The present work has no claim to be called a " Monograph," since it does not even exhaust my own collection of Mon- ticuliporoids, upon which it is entirely based; while a large amount of additional material, much of it new and important, is contained in the cabinets of others or in public museums. Moreover, the group of the Monticuliporoids, from the diffi- culties attending its study, has always been more or less neglected by palaeontologists ; and we may be quite sure that there exist many new and interesting types which yet remain to be discovered. The time, in fact, for writing a " Mono- graph " of the Monticuliporidse has not yet arrived ; and the present work is simply an attempt to ascertain and clearly record the structure of a number of well-marked species of Monticulipora, with special reference to the microscopic and really fundamental characters of these. Palaeontologists, indeed, have now universally recognised that, in such difficult forms as the Monticuliporoids, the microscopic structure is the chief element in the determination of species ; since surface-char- acters may not be recognisable, or may vary greatly according to the state of preservation of the specimens, or other similar circumstances, while mere external form is a most treacherous vi PREFACE. and delusive guide. In some of my own earlier memoirs, deal- ing with species of Monticulipora, I relied, as all palaeontolo- gists did at that time, upon external characters, in so far as these could be observed with a moderate magnifying power ; and I did not recognise the absolute necessity of thin sections for the proper examination of these and similar forms. The result, it need hardly be said, was that the memoirs in question contained various errors, with the nature and extent of which few, probably, are better acquainted than I now am myself. This being the case, I need only say that, with my improved knowledge, I have not in any way attempted to conceal these errors ; but that, on the contrary, I have used at least as much freedom in correcting them as I should have done had I been dealing with the work of others. The absolutely pressing difficulty which, in my opinion, is at present the chief obstacle to the full assumption by Palseo- zoology of its proper place as a truly scientific department of knowledge — a vital branch of the great science of Biology — is that it is almost impossible to recognise and identify so many of the extinct forms of life which have been described and named by the older observers. Every palseozoologist, I feel sure, will, so far as his own special department is con- cerned, bear me out in saying that in the Palaeozoic rocks at any rate, and as regards many groups of animals, not a few types bearing long current titles are either so insufficiently defined that in using them one has no certainty that one is really dealing with the form so named by the original author of the species, or their names are applied by different observers to entirely different organisms. There are few pub- lic or private collections of any extent which would not afford conclusive proof of the truth of the above statement. Nor is it easy to exaggerate the ill effects of this condition of things upon the progress of stratigraphical geology. The determina- PREFACE. vii tion of particular stratigraphical horizons by means of their characteristic fossils is attended with sufficient difficulties even in the Tertiary and Secondary rocks ; but amongst the Palaeo- zoic deposits it has been rendered largely unreliable as regards all but certain particular groups of organic remains, in conse- quence of the fact that it is next to impossible to be sure of the identification of such a large number of typical species. Thus, to take an example from the group now under consider- ation, one may find Monticiilipora petropolitana, Pand., or M. tuinida, Phill., or M. pulchella, E. and H., quoted in lists of characteristic fossils from particular horizons in the Palaeozoic rocks ; but it is not too much to say that in nineteen cases out of twenty there is no guarantee that the identification of such species has been based upon anything else than the almost wholly worthless characters of external form and aspect. Or, one finds such a form as Stcnopora fibrosa, Goldf , or Cho'tetcs lycoperdon, Say, quoted as characterising some particular hori- zon— the real truth being that each of these names has been used to designate several wholly unrelated forms ; while it is almost or quite impossible to determine what is the actual species which the original author of the title had before him. It is unnecessary to multiply examples, either from this par- ticular group of organisms or from any other ; but I take it for almost beyond dispute that the great necessity of Palseozoology at present is not so much to extend its domain indefinitely by the description of new species, as to ascertain the precise extent of its present frontiers by the more thorough elucidation of those forms which have been already named, but have not been sufficiently characterised. It is upon this basis that the present work has been written ; and its main object has there- fore been to record the characters of a number of already partially known forms, the description of new species having been quite subordinated to this. No species, also, has been viii PREFACE. admitted that has not been subjected to a careful microsco- pic examination, and the minute structure is always figured as adequately and fully as considerations of space and cost will allow. For the same reasons, I have not troubled myself greatly about matters concerning the bibliography and synonymy of the genus, chiefly because it will be impossible to take up this part of the subject with much satisfaction or utility until the actual specimens originally examined and described by the earlier workers in this department shall have been investigated by modern methods, and thus, for the first time, clearly and unmistakably identified. It is quite possible, therefore, that when the investigation I have just alluded to has been carried out, and its results published, it may be found that some of the forms which I have here identified with previously described species are in reality distinct from these.^ This source of error, in the present state of our knowledge, seems to be absolutely unavoidable, even by the most careful observer ; and it must be sufficient for me that my descriptions and ^ As an example of this, we may take such a form as Monticnlipora vicwuimlata, D'Orb., commonly cjuoted as one of the characteristic fossils of the Cincinnati Group of Ohio. In determining what species M. Jiiaiiunitlata, D'Orb., really is, we do not o-et any help from D'Orbigny himself, as his description is utterly worthless for pur- poses of identification. We have to fall back, therefore, upon the fuller description and the excellent figures given by Milne-Edwards and Haime of what they believed to be M. inanDiuiIafa, D'Orb. (Polypiers fossiles). It so happens, however, that the Cincinnati Group of Ohio contains three Monticuliporoids, any one of which might be identified with the M. viammulata of Edwards and Haime, so far as form and external characters go, but which differ widely in their microscopic structure. Now, without microscopically examining the actual specimens upon which Edwards and Haime founded their description, it would be impossible to determine which of these superficially similar forms is the actual M. iiiammulata of the French observers ; and one has therefore to choose between the total rejection of this long-current species or the arbitrary selection of any one of these three as really the form originally described. I have followed the latter course, but I freely admit that my selection has been an arbitrary one ; and the form which I call M. viammu- lata, D'Orb., may possibly be shown ultimately not to be really the species which the authors of the ' Poh'liiers fossiles' described under this name. PREFACE. ix figures should be so far accurate, that the forms described, whether rightly identified or not, should be capable of ready recognition by subsequent workers. In my work on ' The Structure and Affinities of the " Tabu- late Corals" of the Palaeozoic Period' (1879), I treated gener- ally of the characters and systematic relationships of Montictdi- pora, and its immediate allies. Part of the matter there given, greatly expanded, and improved by further and more extended investigations, is here reproduced. I have found it necessary, however, to restrict myself upon the present occasion entirely to the genus Monticulipora proper, using this term in its wide sense. Such closely allied types, therefore, as Fishtlipora, M'Coy, Constellaria, Dana, and Dekayia, Edw. and Haime, will only be treated of incidentally. I regret greatly that at the time when I wrote the above- mentioned work I was wholly unaware of the fact that Dr Dybowski had previously (1877) published a treatise on the Monticuliporoids (Die Chaetetiden der Ostbaltischen Silur- formation). I have now, however, had the opportunity of examining this important memoir, and shall, as occasion arises, make such observations upon it as may appear necessary. The material upon which the present work is based is con- tained in my own cabinet, and has been mostly collected by myself from the Silurian, Devonian, and Carboniferous deposits of North America and Britain. I have, however, to thank the kindness of my friends Dr Gustav Lindstrom, Mr Richard Howse, Mr U. P. James, and Mr John M. Nickles, for the gift of various specimens of forms of interest and importance. I have also, where possible, consulted the collections contained in our public museums, though I have not been able to avail myself of this source of information as fully as I should have wished to do. I may add that I have personally prepared the whole of the numerous thin sections required for this work. X PREFACE. The illustrations, with the exception of two of the engrav- ings, have been drawn by myself, and I am much indebted for the fidelity and skill shown by my friend Mr Charles Berjeau, F.L.S., in the transference of these to wood and stone. Where possible, I have employed wood-engravings in preference to lithographs, as it is an advantage in studying minute structures to have the representation of these along with the descriptive text ; but considerations of cost have prevented my using woodcuts as freely as I should have wished. Except in three or four instances, where the contrary is explicitly stated, all the illustrations are original, and are taken from specimens and slides In my own collection, — the latter being drawn by means of the camera luclda. Finally, I have to return my most hearty thanks, for kind assistance by way of specimens or advice, or both, to Mr U. P. James, Mr John M. Nickles, Mr Richard Howse, Dr Gus- tav LIndstrom, Mr R. Etheridge, Jun., F.G.S., Mrs Robert Gray, and Dr Daniel QEhlert. No one can be better aware than I am that the present work, at best, can be regarded as nothing more than a starting-point from which more extended and more final investigations can be carried on ; but that it is not even more Incomplete than It actually is, must be largely set down to the generous help that I have received from my fellow-workers. United College, St Andrews, March 15, 1881. CONTENTS. CHAPTER I. PAGE The general history of the genus Monticulipora, D'Orb. — The notices and descriptions of MonticuHpora, previous to the estabhshment of this genus by D'Orbigny — Lonsdale — Insufficiency of D'Orbigny's defini- tion— The genus Nebulipora, M'Coy — King — Milne-Edwards and Haime — The genus Stenopora, M'Coy — Hall — Billings — Eichwald (Chaetetes, Dianulites, Orbipora, Monticulipora) — Rominger — Dawson — De Koninck — Salter — Nicholson — Dybowski (new classification of the Monticuliporoids) — James — Ulrich, . . . . i CHAPTER n. The general and comparative structure of Monticulipora — Definition of Monticulipora, D'Orb., in the wide sense of this term — The form of the corallum and its variations in the Monticuliporoids — Structure of the walls of the corallites, as shown by microscopic sections and by rough fractures — Absence of mural pores — Surface-characters of the cor- allum— Monticules and maculae — Spiniform corallites — Dimorphism of the corallum, and structural differences between the large and small corallites — Insufficiency of this last character, when standing alone, as a basis of classification — Structure and arrangement of the tabulae — Absence of septa and pseudo-septa — Epithecal and opercular structures, . . . . . . . • 3° CHAPTER III. The development of the Monticuliporoids — Views of Dr Lindstrom — Difficulties in the way of accepting these views — The supposed relation- ship between Monticulipora and Heteropora — The general characters and minute structure of the recent Heteropora neozelanica, Busk — Conclusions as to the want of a real relationship between Heteropora and Monticulipora- — Small importance of external resemblances in determining zoological affinities, . . . . • 5^ CONTENTS. CHAPTER IV. Relations of MonticuHpora to allied types — The general structure of Chse- tetes, Fischer, as compared with that of MonticuHpora — The general structure of Stenopora, Lonsd., and the points in which this genus differs from and agrees with Monticulipora — Stenopora Howsii, Nich, — Relations of Tetradium, Safford, to Monticulipora — Affinities of Monticuliporoids and the Helioporidre — Ceramopora, Hall, and its relations to Monticulipora — Heterodictya, Nich., and its relations to Monticulipora, . . . . . . -79 CHAPTER V. The subdivisions of Monticulipora — The theoretical compactness and unity of the genus — The practical convenience of separating Fistuli- pora, M'Coy, Constellaria, Dana, and Dekayia, E. and H., as distinct genera — The general characters of Fistulipora, M'Coy — The structure of the so-called Fistulipora Canadensis, Billings — The general char- acters of Constellaria, Dana — The general characters of Dekayia, E. and H. — The general characters of Monticulipora, D'Orb., in a re- stricted sense — Subdivision of the genus into the sub-generic groups Heterotrypa, Nich., Diplotrypa, Nich., Monotrypa, Nich., Prasopora, Nich. and Eth. jun., and Peronopora, Nich. — Summary of the char- acters of these subdivisions, . . . . . .90 CHAPTER VI. The general characters of the sub - genus Heterotrypa, Nich., and de- tailed descriptions of illustrative species — M. mammulata, D'Orb. — M. ramosa, D'Orb. — M. rugosa, E. and H. — M. Dalii, E. and H. — M. nodulosa, Nich. — M. O'NeaUi, James — M. tumida, Phill.— M. tumida, Phill., var. miliaria, Nich. — M. gracilis, James — M. Andrewsii, Nich. — M. Ulrichii, Nich. — M. subpulchella,^ Nich. — M. monilifor- mis, Nich. — M. Barrandi, Nich. — M. Dawsoni, Nich. — M. Jamesi, Nich.— M. implicata, Ulrich — M. Trentonensis, Nich. — M. Girvan- ensis, Nich., . . . . . . . -103 CHAPTER VII. The general characters of the sub -genus Diplotrypa, Nich., and de- tailed descriptions of illustrative species — Inadmissibility of Dianul- ites, Dybowski — M. petropolitana, Pand.^M. Whiteavesii, Nich. — M. calycula, James, . . . . . . . 155 CONTENTS. CHAPTER VIII. The general characters of the sub-genus Monotrypa, Nich., and de- tailed descriptions of illustrative species — M. undulata, Nich. — M. Winteri, Nich. — M. irregularis, Ulrich — M. quadrata, Rom. — M. clavacoidea, James — M. calceola, Miller and Dyer — M. pulchella, E. and H. — ^^M. petasiformis, Nich. — M. discoidea, James — M. pavonia, D'Orb. — M. briarea, Nich. — M. tuberculata, E. and H., . i68 CHAPTER IX. The general characters of the sub-genus Prasopora, Nich. and Eth. jun., and detailed descriptions of illustrative species — M. (Prasopora) Grayae, Nich. and Eth. jun. — M. Selwynii, Nich. — M. Selwynii, var. hospitalis, Nich. — M. Newberryi, Nich., .... CHAPTER X. The general characters of the sub-genus Peronopora, Nich., and de- tailed descriptions of illustrative species — M. frondosa, D'Orb. — Difficulties in the way of identifying this species — M. decipiens, Rom., identical with the form believed to be M. frondosa, D'Orb. — M. molesta, Nich. — M. Cincinnatiensis, James — M. ? Ortoni, Nich., and its relations to the genus Atactopora, Ulrich, . -215 APPENDIX. The characters of the genus Trematopora, Hall (Dybowski) — the char- acters of the genus DittoJ>ora, Dybowski, . . . .232 Index, ......... 237 LIST OF ILLUSTRATIONS. FIG. I. 2. 3- 4- 5- 6. 9- lO. 1 1. 12. 13- 14. 15- 16. 17. 18. 19. 20. 21. ENGRAVINGS. Cross -sections of the corallites of species of Monticulipora and Chcetetes, ...... Cross-sections of the corallites oi Alonticnlipora, Longitudinal sections of the corallites of species of Monticulipora, Tangential section of Monticulipora iniplicata, Ulrich, Tangential section o( Monticulipora moniliforniis, Nich., Tangential and longitudinal sections of Stenopora Tasmatiiensis Lonsd., ....... Tangential and vertical sections of Monticulipora Sehiiynii, Nich. showing the tabulge, ..... Heteropora neozelanica, Busk, and H. pelliculata, \V^aters, . Minute structure of Heteropora neozelatiica, Busk, . Tangential and vertical sections of Chcetetes radians, Fisher, var., Stenopora Jackii, Nich. and Eth. jun., Tangential and vertical sections of Stenopora Howsii, Nich., Sections of Tetradium minus, Safiford, Sections of Ceramopora Oliioensis, Nich., and Ceramopora, sp., '$>tz'(\QX\'s, oi Heterodictya gigantea,'^'\(3i\., Sections of Fistulipora minor, M'Coy, Sections of Favosites Canadensis, Bill. sp. ( = Fistulipora Cana den sis, Bill.), ...... Sections oi ATonticulipora {Heterotrypa) ramosa, E. and H., Sections of M. ramosa, var. rugosa, E. and H., and AP. ramosa var. Dalii, E. and H., . Sections of Monticulipora {Heterotrypa) gracilis^ James, Sections oi Monticulipora {Heterotrypa) Andrewsii, Nich., . 37 38 40 46 46 48 52 66 69 80 81 82 85 87 89 92 94 1 12 114 126 129 LTST OF ILLUSTRATIONS. xv 22. External characters and minute structure of MonticuUpora {Hetero- trypa) Ulrichii, Nich., . . . . . .132 23. Minute structure of J/tv///V/////>(;;7? (Hettroirypa) snbpi/lcheiIa,'^\c\-\., 135 24. Tangential section of MonticuUpora [Heteroirypa) moniliformis, Nich., ........ 138 25. ^xierndX c\\dixa.c\.ers oi Mo>iticiilipor a {Heterotrypa) James i, Nich., 144 26. M.'\n\\X.Q sixMcXvixe oi MonticuUpora {Ileierot/ypa) Jamesi, l>[\ch.., . 145 27. Tangential section o( MonticuUpora {Heterotrypa) implicata,'\]\x\ch, 148 28. External characters and minute structure of MonticuUpora {Ilctero- t?-ypa) Trentofiensis, Nich., . . . . .150 29. External characters and minute structure of MonticuUpora [Hetero- trypa) Girvanensis, Nich., . , . . .152 30. External characters and minute structure of MonticuUpora {Diplo- trypa) pctropoUtana, Pand., . . . . .159 31. External characters and minute structure of MonticuUpora {Diplo- t?ypa) IV/iiteavesii, Nich., . . . . .163 32. External characters and minute structure of MonticuUpora [Mono- trypa) tmdulata, '^'ich.. (Trenton Limestone,) . . . 171 T,'^. External characters and minute structure of MonticuUpora {Mono- trypa) undulata,'^\c\\. (Hudson River Group,) . . 173 34. External characters and minute structure of MonticuUpora {Mono- try pa) Winteri, Nich., . . . . . .175 35. External characters and minute structure of MonticuUpora {Mono- trypa) irregularis , Ulrich, . . . . .178 36. External characters and minute structure of MonticuUpora {Mono- try pa) quad rata, Rominger, . . . . .181 37. External characters and minute structure of MonticuUpora {Mono- trypa) clavacoidea, James, . . . . .184 38. External characters of MonticuUpora {Monotrypa) pulchella, E. and H., ....... 188 39. Minute structure of MonticuUpora {Monotrypa) pulcheUa, E. and H., ....... 189 40. External characters and internal structure of MonticuUpora {Mono- trypa) petasif or mis, Nich., . . . . .191 41. MAxmio. 'sXx\xc\.\xxt oi Moiiticulipora {Alonotrypa) pavonia,XyOx\)., . 197 42. MonticuUpora {Prasopora) GraycE, Nich. and Eth, jun., . . 204 43. Minute structure of MonticuUpora {Prasopora) Grayce, Nich. and Eth. jun., ....... 205 44. External characters and minute structure of MonticuUpora {Praso- pora) SelwynU, Nich. (Trenton Limestone,) . . . 208 45. External characters and minute structure of MonticuUpora {Praso- pora) Selzcynii, var. hospitalis, Nich. (Cincinnati Group.) . 210 xvi LIST OF ILLUSTRATIONS. 46. Minute structure oi Alonticulipora {Fero/wpora) froudosa, D'Orb., . 218 47. Minute structure of a typical example of AlonticiiUpora dccipiciis, Rom., ........ 223 48. Minute structure of Trematopora coUiadata, Eichw. sp. (Copied from Dybowski,) ...... 233 49. Enlargement of a fragment of Dittopora aiuiulata, Eichw. sp. (Copied from Eichwald,) ..... 234 50. Minute structure of Dittopora davceformis, Dybowski. (Copied from Dybowski,) ...... 235 PLATES. I. MonticuHpora {Heterotrypa) mofiiliformis, Nich. ; M. {Heterotrypd) Bar- randi, Nich.; M. {Monotrypd) cakeola, IMiller and Dyer; M. {Hetero- trypa) nodulosa, Nich. II. MonticuHpora {Heterotrypa) gracilis, James; M. {Heterotrypa) ramosa, D'Orb. ; M. {Monotrypa) briarca, Nich. ; M. {Feronopora) Cinciii/iaii- ensis, James ; M. {Heterotrypa) ii/iplicata, Ulrich. III. MonticuHpora {Heterotrypa) tumida,Y\\\\\.; M. {Heterotrypa) ONcalli, James ; M. {Feronopora) ? Ortoni, Nich, IV. MonticuHpora {Frasopora) Nezvberryi, Nich,; M. {Monotrypa) tubercu- lata, E, and H. ; AI. {Monotrypa) discoidea, James ; M. {Diplotrypa) calycula, James. V. MonticuHpora {Heterotrypa) Andretvsii, Nich. ; M. {Heterotrypa) subpul- c/iella, Nich. ; M. {Heterotrypa) Datvsoni, Nich. ; M. {Feronopora) frondosa, D'Orb. VI. MonticuHpora {Heterotrypa) mammulata, D'Orb. ; M. {Feronopora) mo- iesta, Nich.; M. {Monotrypa) pavonia, D'Orb. THE GENUS MONTICULIPORA. CHAPTER I. THE GENERAL HISTORY OF THE GENUS MONTICULIPORA. Genus Monticulipora, D'Orbigny, 1850. (Prodr. de Paleont, t. i. p. 25.) Nebulipora^ M'Coy, Ann. Nat. Hist., ser. 2, vol. vi. p. 282, 1850. Orbitulites, Eichwald, Zool. spec, t. i. p. 180, 1829. Orbipora, Eichwald, Leth. Rossica, t. i. p. 484, i860. Stenopora, M'Coy? (non Lonsdale), Brit. Pal. Foss., p. 24, 185 1. The genus Monticulipora was founded by D'Orbigny in 1850 (Prodr. de Pal., t. i. p. 25, where the date of the genus is given as 1847), the only definition being: "cellules serrees, poriformes a la surface, d'un ensemble rameux ou encroutant couvert de petites saillies coniques." The first species given under this definition is the M. mammulata, D'Orbigny, of the Lower Silurian of the United States, which must therefore be accepted as the type of the group. It will be quite obvious that the only character in the above definition which has the very remotest generic value, is the existence of conical eleva- tions or " monticules " upon the surface, and even the nature of these elevations is left wholly undefined. I may add, also, that there are unquestionable species of Monticulipora in which "monticules" are wanting. The genus Nehdipora, M'Coy, a -2 THE GENUS MONTICULITORA. (A.nn. Nat. Hist., ser. 2, vol. vi. p. 282, Oct. 1850), was founded in the same year as Monticulipora, and includes forms unques- tionably congeneric with the latter, though I am unable from his figures and descriptions to be sure as to the precise species upon which M'Coy founded his genus. This point, indeed, could only be set at rest by an examination of the original specimens in the Woodwardian Museum, which I have unfor- tunately had no opportunity of inspecting. It is, however, a matter which, I think, will still admit of discussion, as to whether or not M 'Coy's Nebidipora should not be adopted as the title for the fossils now under consideration, rather than the Monticulipora of D'Orbigny. I am not able to decide this point, and I will only remark further, that M'Coy, in his generic diagnosis, states that the walls of Nebidipora are "apparently perforated by rows of small foramina," though he does not allude to this character again, and seems to have been doubtful as to its actual existence. The typical MonticuliporcB are undoubtedly devoid of mural pores ; but I have examined (through the kindness of my friend Mr R. Etheridge, jun.) a specimen from the Wenlock Limestone of Dudley in the col- lection of the British Museum, which has all the external and general characters of such a Monticulipora as M. petropolitana, Pand., but in which the walls of the corallites are unquestion- ably minutely porous. It is not impossible, therefore, that it is upon some such specimen as the preceding that M'Coy founded the statement that I have referred to. Earlier than either Montictdipora, D'Orb., or Nebidipora, M'Coy, are the names Orbittdites and Dianidites, proposed by Eichwald (Zool. spec, 1829) for certain Silurian fossils, some of which, at any rate, are forms of Monticidipora. The first of these two names cannot, however, be retained, as it is identical with the previously named Foraminiferous genus Orbitulitcs {Orbitolites) of Lamarck (An. sans Vert., 1801), a genus which has subsequently held its ground. As for the genus Dianulites, Eichw., it is possible that the forms placed in it by this distinguished palaeontologist are really referable GENERAL HISTORY. 3 to Montiadipora ; but as this certainly could not be definitely settled by an appeal to Eichwald's figures and descriptions, it would not be reasonable to allow this to supplant such later and well-defined names as Nebtdipora, M'Coy. I shall afterwards discuss the question as to whether or not Di~ amdites, Eichw., has any claim to stand as a sub-genus of Montictdipora. Since the establishment of M 'Coy's genus Nebtdipora, the name Monticulipora^ D'Orb., has either been accepted as valid, or the fossils generally grouped under this head have been referred to Chcstetes, Fischer. The above are the most salient points in the earlier history of Montiailipora as a genus ; but it may be advisable that I should give here a more detailed account of the chief papers and works which have dealt with this group of corals. In so doing, however, I shall not pretend to give an absolutely exhaustive bibliography; nor shall I, in general, notice memoirs which are simply descriptive of species, unless there should be some special reason to the contrary. My object, in fact, is simply to record in order the principal accessions to our know- ledge of the genus since it was first founded, and to discuss briefly certain points which could not well be treated of except in such a historical summary. Previous to the establishment of the genus Montiadipora by D'Orbigny, such species as were then known to palaeontolo- gists were placed under various genera. Thus, by Pander (Beitrage zur Geogn. des Russ. Reiches, 1830), Goldfuss (Petref. Germ., 1833), Phillips (Geol. York- shire, 1836), Lonsdale (in Murchison's Silurian System, 1839), Portlock (Geol. Rep,, 1843), and De Koninck (An. Foss. des Terr. Garb., 1842), they were, wholly or in great part, referred to Calamopora or Favosites ; while other writers either followed the same course, or referred them to genera equally remote from their true position. Of these older works, the one prin- cipally deserving of mention is Lonsdale's memoir in the ' Geology of Russia in Europe and the Ural Mountains' (Ap- 4 THE GENUS MONTICULIPORA. pendix A, 1845), a memoir which, Hke all the productions of its author, bears ample proof both of conscientious labour and of unusual sagacity and acumen. In this, Mr Lonsdale accurately recognises the chief differences between Chcstetes, Fischer, and the forms which we now group under Monticulipora, D'Orb. — a difference which many subsequent observers were slow to appreciate ; though he erroneously refers to CJicetetes the M. petropolitana of Pander {pp. cit., p. 596). The Stenopora spinigera, Lonsd., and 6". crassa, Lonsd., of the same work (p. 632), are not described or figured with such fulness that it would be possible to arrive at any final decision as to whether they are true Stenoporce, or are really referable to Montictdi- p07'a. As they are of Permian age, the presumption would be that they really belong to Stenopora ; but nothing short of a microscopic examination of actual specimens could settle this point. In 1850, as previously stated, the genus Monticiilipora was founded by D'Orbigny (Prodr. de Paleont., t. i. p. 25), and four species (viz., vJ/. viainmulata, D'Orb., M. ramosa, D'Orb., M. froiidosa, D'Orb., and M. filiasa, D'Orb.) were placed under it. Not only, however, was the generic definition exceedingly vague, but it is to be noted that on the same page of the same work D'Orbigny puts such well-marked types of Alonticidipora as M. petropolitana, Pand., and M. rttgosa, E. and H. (the last being really only a variety of M. raniosa, D'Orb.), under the head of Chcstetes, Fischer. Various other species of Monticnlipora are noted by D'Or- bigny in other parts of the " Prodrome," but they are placed under different genera {Ptilociictya, Ceriopora, Favosites, &c.) It is, moreover, to be remarked, that in the case of the four species above mentioned as placed under Monticidipora, the descriptions, being unaccompanied by figures, are quite insuffi- cient for specific identification, and that their survival at all is really due to the excellent work subsequently done by Milne- Edwards and Haime (Polypiers Fossiles). In the same year (1850) as the publication of the genus GENERAL HISTORY. 5 MontictUipora by D'Orbigny, but apparently at a somewhat later date, an important paper was published by tinu°ecL°"' M'Coy on "Silurian Radiata" (Ann. Nat. Hist, sen 2, vol. vi. p. 282). In this memoir Professor M'Coy founded the genus Nebulipora, with the following definition : — " Corallum encrusting or forming lenticular masses, with a concentrically wrinkled epitheca below ; composed of small prismatic tubes, perpendicular, or nearly so, to the upper surface on which they open ; among the small tubes are regularly arranged clusters of similar tubes of rather larger size. All the tubes in contact, traversed by horizontal dia- phragms at regular distances (walls apparently perforated by rows of small foramina)." The species described under this head are Nebulipora cxplanatay M'Coy, A'", lens, M'Coy, and N. papillata, M'Coy, all from the Silurian rocks. I have never had the opportunity of examining authentic specimens of any of these forms ; but the descriptions given of them, and the subsequently published figures (Brit. Pal. Foss., PI. I. c), prove beyond a doubt that they belong to Monticulipora, D'Orb. Under these circumstances, the genus Nebulipora, M'Coy, must be taken as a synonym of Montictdipora, D'Orb., in spite of the fact that it was scientifically and recognisably defined, which certainly cannot be said of the latter. The only ground (presuming that Moiiticulipora, D'Orb., really was published first) upon which Nebulipora could be re- tained, would be its possession of perforated walls to the corallites ; but this observation was only put forward doubt- fully by M'Coy, and there can be little doubt that it is with- out a basis in fact. In 1850, Professor King described a coral from the Permian rocks of England (Mon. Perm. Foss., p. 28) under the name of Steiiopora coluninaris, Schloth., which may possibly be a MonticiUipora. This is of interest, as it is questionable if we can as yet definitely assert that we are acquainted with any species of Monticulipora from deposits later than the Car- 6 THE GENUS MONTICULIPORA. boniferous. The materials, however, for deciding the true affinities of the coral in question are insufficient ; and it is quite possible that we have really to deal in this case with a Ste7Wpora, to which genus the Calainopora Mackrothii, Gein., may also belong. In 185 1, Milne-Edwards and Haime published their great work on the Palaeozoic Corals (Polypiers Fossiles des Terrains Palseozoiques), a work which will always be one of the classics of the zoophytologist. So far as the present genus is concerned, the French observers threw the weight of their high authority against the acceptance of the genus Monticidipora, D'Orb., though, as will afterwards be seen, they subsequently altered their views upon this subject. They described, however, a large number of species of Mon- ticiilipora, referring these to the genus Chcetetes, Fischer. Though the descriptions of these species — as was inevitable at the time when the work was written — are not based upon the minute methods of modern palaeontology, still it is not too much to say that Milne-Edwards and Haime laid here the foundations of our scientific knowledge of the genus Monti- citlipoi^a ; and most of the species which they described have since been accepted by later workers in the same field. It is not necessary to enumerate in this place the numerous species of Montiadipora which Milne- Edwards and Haime described or noticed in the " Polypiers Fossiles," nor to discuss the characters of these, especially as many of them will be fully treated of later on. It may be added, however, that the authors rejected the genus Stcnopora, Lonsd., and grouped the species which had been referred to it under Chcstetes, Fischer.^ In the same year M'Coy republished (Brit. Pal. Foss., p. ^ In earlier publications (Comptes Rend., xxix. p. 261, 1849, and Introduction to the 'Monograph on the British Fossil Corals,' p. Ixi., 1850) Milne-Edwards and Haime accepted the genus Stenopora, Lonsd., but take as their type S. spinigera, Lonsd., ignoring the characters upon which Lonsdale really based his genus, and introducing as the special characteristic of the genus the non-essential feature of the presence of spines at the angles of the calices. GENERAL HISTORY. 7 22) his description of the genus Ncbu/ipora, which had formerly appeared in the 'Annals of Natural History,' and I 51 con- £orured the three species of the s^enus which had been described in the latter periodical. He also defined the genus Stenopora as follows : — " Polypidom polymorphous, composed of round or poly- gonal tubes radiating from an imaginary axis to the surface, where the bounding-ridges are tuberculated ; young tubes interpolated by lateral budding between the old ; tubes con- stricted at irregular distances in planes parallel with the surface, and partially closed at the orifice by a concave dia- phragm perforated in the centre ; no connecting tubuli nor foramina." The species described under the head of Steno- pora are S. fibrosa, Goldf sp. (with two varieties — viz., van lycopoditcs, Say, and var. regularis, M'Coy), S. ? granulosa., Goldf. sp., 6". infiaia, De Kon. sp., and 6". iiimida, Phill. sp. With the exception of the last of these, it is probably impos- sible for any one who has not examined the original speci- mens which Professor M'Coy had in his possession, to decide with any preciseness what were the forms upon which he actually based his determinations of these species. It may, however, be taken as tolerably certain that the forms which M'Coy described under the names of S. fibrosa (with its varieties) and 6^. hmtida, are, at any rate, not referable to Stenopora, Lonsdale, and that they are probably true Monti- culiporce. It is therefore certain that Stenopora, M'Coy, is not an equivalent of Stenopora, Lonsd., and it may be regarded as almost certain that it is a mere synonym of Alonticnlipora, D'Orb. As to what may be the true nature of the forms described by M'Coy under the names of Stenopora ? granulosa^ Goldf. sp., and 5*. inflata, De Kon. sp,, nothing positive could be said without the previous examination of the original specimens. In the same year (1851) appeared the second volume of the magnificent ' Palaeontology of New York,' by Professor James Hall. In this work Professor Hall figured a species of Mon- 8 THE GENUS MONTICULIPORA. ticulipora under the name of Chcstetes lycoperdon, from the Niagara group of North America. The same so- 1 8s I con- (,^iig(;j species had been previously (1847) described and figured, along with others, in the first volume of this work (p. 64, PI. XXIII., figs, i-i ?; 2, 2a, 3, and PI. XXIV., figs. \ a-\ 0), where it is stated to be founded upon the Fa- vosites lycoperdon of Say, though it would seem that Say did not really publish this name, and that it was first actually made public by Vanuxem (Geol. 3d Dist. N. Y., p. 46, 1842) under the name of Favosites lycopodites (see Note by Professor C. A. White in 'The Palaeontologist,' No. 3, p. 20, 1879). My object in mentioning this in this place is twofold. On the one hand, there are few corals which have been more commonly quoted by American geologists and palaeontologists than Chcetetes lycoperdon, Say, or ChcBtetes lycopodites, Vanuxem ; and it would therefore be very desirable to establish, if possible, the precise nature and characters of the form to be understood by this name, thouoh I am not aware that this has ever been satisfactorily accomplished. On the other hand, I wish to record the opinion that the generally laudable desire of pre- serving an old name, where this is possible, may sometimes be carried too far, and that this is, in my view, an instance in point. No definition of Chcstetes lycopodites, Vanuxem, which can be regarded as in any sense a definition, was given by its original author, or has since been supplied by any subsequent observer, while it is certain that this name (or the equivalent, C lycoperdon, Say) has been applied by different writers to wholly different forms. A reference to Professor Hall's plates {loc. cit.), for example, will at once show that even this accurate and accomplished observer included more than one specific form under this title. Nor, in the case of a genus like Monticuli- pora, where external form goes for so little, can Vanuxem's original figure, however good, be regarded as satisfactory proof as to the species upon which he really founded the name in question. Under these circumstances, therefore, I think, as I think about such names as Favosites fibrosa, Goldf , and vari- GENERAL HISTORY. 9 ous other similar titles, that it would be a real gain to science if there could be a general aoreement that desiornations of this kind — published, in the first place, with wholly insufficient definitions, and subsequently employed by others in widely different senses — should be dropped altogether, and that no attempt should be made to revive them. I know that there is much that could be urged on the other side of this question and that it mio;ht be difficult to draw a line between cases such as I now speak of, and others where the original author had simply made more or less serious errors in the definition of his species ; but I feel sure that every working naturalist must have experienced the hardship of finding himself confronted by specific names, which he cannot identify by reference to original descriptions, and which others have obviously applied to more than one class of objects ; and I think it would not be very difficult to specify the cases in which this hardship is so great that the abandonment of the original name becomes a proper remedy for it. In 1854, Milne-Edwards and Haime published the conclud- ing portion of their admirable ' Monograph of the British Fossil Corals,' dealinor with the corals of the Silurian formation. This work is chiefly deserving of notice in this connection because its authors here (p. 264) retracted the opinion which they had previously expressed as to the identity of MonticiUipora, D'Orb., with Chcetetes, Fischer, and accepted the former genus as sufficiently distinguished by its gemmiparous method of reproduction. The species which they describe are M. petropolitana, Pand., M. papillata, M'Coy, M. Fletcheri, E. & H., M. pulchella, E. & H., and M. Bower- banki, E. & H. ; while they reproduce M 'Coy's descriptions of his M. i^Nebulipora) cxplaiiata and M. {Ncbulipord) lens. Of the above-mentioned forms, M. Boiverbanki, as I have else- where shown (Pal. Tab. Cor., p. 72), is a Favosites, while M. pulchella is a valid and genuine species of Monticulipora ; but the forms described under the names of Af. pch^opolitana, Pand., M. papillata, M'Coy, and M. Fletcheri, E. & H., must remain lo THE GENUS AIONTICULIPORA. to some extent uncertain, till it may be possible to examine microscopically the original specimens upon which Milne- Edwards and Haime founded their determinations. In 1859, Mr Billings described (Canad. Nat., vol. iv. p. 427) some species oi Monticulipora from the Silurian rocks of Canada, referring these to the genus Stenopora, Of the forms in question, two {S. patula and S. adhcBvens) are described as new species ; but the descriptions given are so vague and so brief, that it would be impossible to recognise their validity until the original specimens can be re-examined and described. In i860, D'Eichwald published the first volume of the ' Lethaea Rossica,' in which various forms of Monticulipora were described. These were referred to the o-enera CJicb- tdes, Fischer, Dianulites, Eichw., Orbipora, Eichw., and Monticulipoi^a, D'Orb., and possibly to one or two other genera (such as Myriolithcs). As the attempt has recently been made by Dybowski to resuscitate the genera DianuliteSy Eichw., and Orbipora, Eichw,, it may be as well to supply here a brief analysis of the account which D'Eichwald gives of the above-mentioned four genera, and of the forms which he in- cludes under them. In so doing, I may premise that much of this portion of the ' Lethaea Rossica ' was really published by Eichwald in the ' Zoologia specialis' (1829), to which, unfor- tunately, I have not access. At the same time, the ' Lethaea Rossica' contains the matured views of Eichwald as to these and other genera, and it seems only fair to take an author's emended diagnosis as the basis for any criticism of his views : — With reeard to the eenus Chcetetes, Fischer, Eichwald recoe- nises that it is separated from Monticulipora, D'Orb., by its fissiparous mode of development, and he places under this head eight species — viz., C. heniisphcBricus, Eichw., C. pyri- f or mis, Eichw., C. apiculatus, Eichw., C. anmilatus, Eichw., C, fastigiatus, Eichw., C. cylindraceus, Eichw., C. radians, Fisch. and C. tumidns, Phill. With regard to the great majority of these, it is quite within the mark to say that it would be GENERAL HISTORY. ii impossible to form any opinion as to their true nature by a mere perusal of the descriptions which are given of them, or an examination of the figures by which they are accompanied. No observer, therefore, who had not access to Eichwald's original specimens, could hope to arrive at any conclusion as to even the generic affinities of most of the above — to say nothing of their value as species. The most of them (excluding C. radians, Fischer) would seem to be probably Monticiiliporce, while the form described as C. annnlatus looks like a Polyzoon, but would seem from Dybowski's description (Die Chaete- tiden, p. 86) to be a Monticuliporoid. This is probably the utmost that could be safely asserted. The genus Orbipora, Eichw., is defined as having a discoid corallum, convex above and flat below, composed of vertical cylindrical tubes. The calices are said to be oval below and hexagonal above, all of them equal in size. Tabulae are said to be wanting or rudimentary ; multiplication is by gemmation, and there is a basal epitheca. The species described under this head are Orbipora distinct a, Eichw., and O. fungiformis, Eich. ; but neither could be identified by the descriptions or figures which are given, unless the observer possessed authen- tic specimens to refer to. All that can be stated is, they appear to be discoid forms of Monticulipora. It will be ob- served, however, that in his definition of Orbipora, Eichwald brings forward one structural character (namely, the absence or rudimentary condition of the tabulae), which, if confirmed, and if found to be associated with other structural peculiarities, might possibly afford some justification for the revival of the generic title. The genus Dia7iulites, Eichw. (Leth. Ross., p. 487), is de- fined as having an obconical, attenuated, gemmiparous, and ramose corallum, which is fixed by its base, and covered with a thick epitheca below. The corallum is composed of vertical tabulate tubes, which diverge irregularly from the base, and are surrounded by a spongy " coenenchyma." The sides of the corallum are largely grooved, with transverse sulci, indi- 12 THE GENUS MONTICULIPORA. eating increments of growth. The two species described under this head are D. detritus, Eichw. (which Eichwald expHcitly states to be the type of the genus— /(?<:. cit., p. 487), and D.fastigiatns, Eichw. The two species in question are quite indeterminable, so far as Eichwald's descriptions and figures would serve this purpose.^ The figures which are o-iven of these forms would seem to be inverted; but this may not really be the case. There is nothing, however, either in the figures or text, which would enable us to decide whether these types are referable to Monticulipora, or Fistiilipora, or Prasopora, or to some other Monticuliporoid type. So far as the structural characters of the genus Dianulitcs are concerned, the presence of a thick lateral epitheca, though strongly insist- ed upon by Eichwald in his remarks upon the genus, cannot be regarded as of any special importance ; and the only funda- mental character mentioned is, that the tabulate corallites are surrounded by a " spongy coenenchyniar This character, being common to many Monticuliporoids — since the "interstitial tubes" of these are the " coenenchyma " of the older writers — cannot, however, constitute alone a basis for generic separation. I shall subsequently give my reasons for rejecting Dian- iUites, Eichw. (emend. Dybowski), these reasons being partly that I do not regard the genus (as redefined) as a natural divi- sion, and partly that I do not admit the propriety of endeav- ourino- to restore old generic names which were originally defined in an absolutely worthless manner.- In the meanwhile, 1 Dybowski (Die Cha;tetiden, pp. 20, 21) states that D. detritus and D. fastigi- atus are merely different conditions of tlie same species, for which he retains the latter name; and he further considers Clicetetes Fa/ideri, E. and H., to be a syno- nym of this. For my own part, I cannot recognise the reasonableness of setting aside a (by comparison) well-characterised type, such as the C. Panderi of Ed- wards and Haime, in favour of a type so defined originally as to be beyond pos- sible recognition — even though an observer, fortunate enough to have access to the original specimens, should ultimately be able to show that these possess characters entitling them to generic or specific distinction. 2 I entirely endorse, on the other hand, the proposed rule of the Committee of the International Geological Congress on Pateontological Nomenclature, that " le nom attribue a chaque genre et a chaque espece est celui sous lequel ils ont ete le plus anciennement designes, a la condition que ce nom ait etc public ct claire- mcnt deJiniP The Eichvvaldian genera of Monticuliporoids do not even approxi- GENERAL HISTORY. 13 in justice to Dybowski, it must be stated that he has founded his Diamdites, not upon the later definition of this genus given in the ' Lethsea Rossica,' but upon the earHer definition given by Eichwald in the ' Zoologia speciaHs ' (vol. i. p. 180, 1829). It is really not worth while taking up space with reproducing from Dybowski's work this earlier definition, which Dybowski justly speaks of as " diese nichtssagende Charakteristik." I will only notice, that the definition might apply to a score or more of known genera of Corals or Polyzoa, with equal pro- priety, as it does not include a single character of generic value ; and that there is certainly no mention in it of the " spongy coenenchyma" so strongly insisted upon in the later definition. At the same time, provided that, as in this case, no other observer has in the interval meddled with the genus, it is surely only reasonable to take an author's latest and e^nended definition as the basis for further and better investigation, rather than his earlier diagnosis. Lastly, Eichwald defines Montiailipora^ D'Orb. (Lethaea Ross., p. 492), as comprising forms with a semiglobose, ovate, or depressed corallum, the surface of which is covered with small elevations, while the base is flat and concentrically striated. The corallum is said to be composed of delicate tubes alternating with fascicles of larger corallites, with round- ed calices, and the walls furnished with minute irregular com- municating pores ; while there are horizontal and close-set tabulae. It is not necessary to discuss this definition, as the only species which D' Eichwald places under it {M. ovuhim, Eichw.) appears to be undoubtedly a Heliolites, or, at any rate, to belong to the Hcliolitidce. The next important contribution to our knowledge of the Monticuliporoids was a memoir by Dr Rominger, entitled " Observations on Cheetetes and some related Gen- era, in regard to their Systematic Position ; with an appended Description of some New Species" (Proc. Acad. mate to a fulfilment of this last essential condition, and, in my opinion, ought to be unhesitatingly rejected. 14 THE GENUS MONTICULIPORA. Nat. Sci. Phil., 1866, p. 113). In this memoir Dr Rominger expresses the opinion that Chcstetes, Fischer (under which he includes Monticidipora, D'Orb., and various allied types), is really referable to the Polyzoa, and not, as at that time gen- erally believed, to the Actinozoa. He regards the interstitial corallites of the Monticuliporoids — which he rightly recognises as being more closely tabulate than the normal corallites — not as " real tubules," but as " merely vertical rows of independent cells, which, being crowded in between tubes, assumed them- selves the form of tubules." He notices the existence of oper- cula in M. rugosa, E. and H., M. ramosa, D'Orb., and M. frondosa, D'Orb., pointing out that in the latter these structures (which, I may add, are morphologically only the last formed tahdcE) are concave and have an excentric opening. He also alleges that septal ridges sometimes occur, and instances some specimens of M. frojidosa, D'Orb., from Cincinnati ; but it is probable that in this case he has been misled by the inward protrusion into the visceral chambers of the large corallites of the " spiniform corallites" in the substance of their walls. In addition to describing various species of Monticulipora proper, Dr Rominger further describes a number of types of Fishili- pora (and Callopora^ Hall) ; but as the descriptions are short, and are unaccompanied by any figures, it will probably be difficult to identify many of these in future. In the second edition of the 'Acadian Geology,' published in 1868, Principal Dawson figures and briefly describes two small Monticuliporoids from the Carboniferous rocks of Nova Scotia under the names of Chcstetes t7imidtts, Phill., and Stenopoi'a exilis, n. sp. Dr Dawson was good enough to send me specimens of these, but the material was unfortunately insufficient for a satisfactory examination by thin sections ; while in the case of the latter form, the few specimens at my disposal were preserved so badly (appar- ently in dolomite) that I failed to prepare any workable slides from them. I should not, therefore, wish to express any opinion as to their precise nature. GENERAL HISTORY. 15 The latest views of Professor De Koninck upon the genus Montictilipora, so far as I am aware, are contained in his ' Nouvelles Recherches sur les Animaux Fossiles du 187'' Terrain Carbonifere de la Belgique ' (p. 141), published in 1872; though his earlier publications (An. Foss. du Terr. Carb.) contain also descriptions of species of the genus. In the work just mentioned, M. De Koninck briefly defines the genus Montictdipora, D'Orb., and describes under it as species M. tumida, Phill., and M. ? injiata, De Kon. It is singular to find this eminent palaeontologist doubtful, in his definition of the genus, as to two such important points as the presence or absence of septa, and the complete or incomplete con- dition of the tabulae, and subsequently even inclined to question if tabulae exist at all in the genuine species of Montiailipora. On the other hand, it is interesting to find so high an authority disposed to refer the genus to the Alcyonaria, rather than to the Zoantkaria. With regard to the two species described by De Koninck, it may be observed that it is questionable if M. ? inflata be a Motiticulipora at all ; while the form termed M. iumida, Phill., does not appear to be identical with the form understood generally under this name by British palaeontolo- gists, and, judging from the description and figures, would seem to probably include more than one species. Mr Salter, in his last published work (Cat. Foss. Woodw. Mus., 1873), regards Montmdipoj'a as a synonym oi Nebulipora^ M'Coy, while he, at the same time, places some species of the genus under Stenopora. In 1874, I published a paper on species of Ckcsieies from the Lower Silurian rocks of North America (Quart. Journ. Geol. Soc, vol. XXX. pp. 499-515, Pis. XXIX., XXX.), in which were discussed the affinities of the genera Cha:teteSy Stenopora^ and Montiailipora. As the microscopic structure of all these three genera was at that time unknown, or imper- fectly known, I concluded that the external characters and more evident internal features did not afford sufficient basis for the establishment of the genus Monticulipora, as separate 1 6 THE GENUS MONTICULIPORA. from ChcEtdes, Fischer. I also came to the conclusion that the American corals usually referred to Stenopora could not be so placed, unless Lonsdale's definition of this genus were extended and modified. Several forms believed to be new were described, of which some are really synonyms of previously recorded species, w^hile one (C delicatulMs) turns out, on microscopic examination, to be a Polyzoon. In the same year I also pub- lished descriptions of three new species of Montictilipora, which I described under the names of C/i^tctes monilifomnis, C. Bai^- randii, and C. quadrangular is (the last possibly a Polyzoon), all from the Devonian rocks of Canada (Geol. Mag., Dec. 2, vol. ii., and Palaeontology of Ontario, pp. 60, 61). In the same year Mr R. Etheridge, jun., published (Ann. Nat. Hist., ser. 4, vol. xiii. p. 194, PI. XI. figs. 1-3) some interestinsf observations on the structure and external char- acters of AI. ttimida, Phill, as based upon specimens derived from the Carboniferous rocks of Scotland. In 1875, Mr U. P. James, an enthusiastic student of the Cincinnati fossils, to whom I am indebted for much friendly assistance, published the second edition of his ' Cata- loeue of Lower Silurian Fossils of the Cincinnati Group,' in which he described four new species of Monticuli- pora, under the names of Chcctdcs ? calyciila, C. clavacoideus, C. Cincinnatiensis, and C. O" Nealli. All these are excellent and interesting species, and will be described in detail in the later portion of this work. The last is the same as C. sigillarioidcs, Nich., which was published some two or three months subsequently to the appearance of Mr James's catalogue. In the same year, but at a little later date than that of the publication of the preceding, appeared the second volume of the ' Palaeontology of Ohio,' in which I gave descriptions of a number of Monticuliporoids. Many of these had been previ- ously described by me in the ' Quarterly Journal of the Geo- logical Society' (vol. xxx.), but some additional forms were here described as new. As in the paper just alluded to, and for GENERAL HISTORY. 17 the reasons previously given, all the species of JMonticulipora were placed under the head of CJicetetes, Fischer. In 1876, a paper was published by me (Ann. Nat, Hist, sen 4, vol. xviii. p. 85, PI. v.), in which I corrected several errors into which I had been led in my formerly published descriptions of species of Monticulipora from the Lower Silurian rocks of North America, and at the same time gave a brief account of some of the more salient features exhibited by microscopic sections of various species of the genus. In 1877, Dr Dybowski published a most important work upon the Monticuliporoids, entitled ' Die Chsetetiden der Ost- baltischen Silur-formation.' I regret greatly that I was not aware of the existence of this work till within the last two or three months, and that I was therefore entirely unacquainted with it at the time that I published my work upon the Palaeozoic " Tabulate Corals." Dr Dybowski's work is, unfortunately, of much less value than it would otherwise have been, owing to the fact that his material was derived for the most part from a very limited area, and also that he has greatly hampered himself by his desire to restore the old Eichwaldian genera. For my own part, therefore, while doing every justice to the great advance in our knowledge effected by Dr Dybowski's work, I am sorry to find it impos- sible to accept the greater part of his general conclusions. At the same time, the work in question not only shows remarkable industry, but is the first systematic attempt to deal with the Monticuliporoids by means of modern methods of inquiry ; and it thus is entitled to a full consideration. I shall therefore give in this place a tolerably full analysis of its con- tents ; though I do not think it necessary to notice more than its most salient points, and I shall subsequently have occasion to speak of some of its secondary features. In the first place, as regards nomenclature, Dr Dybowski proposes the following terms {loc. cit., p. 9) : Each individual corallite of the colony he designates by the name of a " Poly- pit ; " but it hardly need be remarked that this term would be i8 THE GENUS MONTICULIPORA. regarded by English naturalists as a very objectionable one, since the term "polypite" has become indissolubly connected with the Hydrozoa. " Axenhohle " is defined as the cavity found in the long axis of a cylindrical or dendroid corallum, which is not provided with a special lining membrane. So far as I have seen, the occurrence of such a cavity is purely accidental, and is due to the dissolution of the central portion of the corallum prior to fossilisation, or to the fact that the foreign body upon which the colony grew has been removed in a similar fashion, I do not think, therefore, that any special term is needed to indicate the presence of such a phenomenon. On the other hand, the name of " Axenrohr " is given to the axial tube of certain forms like Stenopora colmmiaris, Dyb., where the cavity is lined by a special mem- brane. I have never observed any such cavity in any Monti- culiporoid — except, perhaps, in M. calceola, Miller and Dyer — and can therefore pronounce no opinion as to its real nature and value. The term of " Wandrohrchen " or " Porenkanal- chen " is proposed for delicate canals or tubuli which run in the walls of the corallites, and parallel with the long axes of these; and the name of" Hockerchen" is given to the super- ficial spiniform projections of these. These structures are identical with those which I shall subsequently describe under the name of " spiniform corallites," and I take an entirely different view as to their nature from that held by Dybowski. As will be subsequently seen, I regard them as being in no way analogous to the " intramural canals " of many " Tabulate Corals," but as representing a peculiarly modified series of corallites ; and the name of " Wandrohrchen " would thus be an inappropriate one. The name of " Wandstrange " is given by Dybowski to what he describes as " dendritic or streak-like (' streifenartig '), solid, sclerenchymatous structures which are situated on the inner side of the walls of the corallites." The above description would have left me quite in the dark as to the nature of the structures referred to by this name ; but after examination of GENERAL HISTORY. 19 Dybowski's figures of forms said to possess " Wandstrange," I have no doubt that the bodies thus named constitute an aborted series of " spiniform corahites," such as can be ob- served to occur in various MonticuHporoids. Dr Dybowski lays considerable stress upon the presence or absence of " Wandstrange ; " but, with the views that I hold as to their nature, they cannot be regarded as possessing any classificatory value. With regard to the other terms employed by Dybowski, it is only necessary to remark that, in accordance with the views generally held at the time, he regards the " interstitial tubes " of so many of the MonticuHporoids as being of a ccenenchymal nature. W^henever, therefore, he speaks of the absence or presence of "Coenenchym" in any given species, he is to be understood as meaninof that " interstitial corallites " are absent or present. Mr Moseley's researches on HeliopoTa and Mille- pora have rendered it almost certain that the interstitial tubes of the MonticuHporoids are of the nature of a peculiar group of modified corallites, and we can therefore no longer with propriety speak of them as " coenenchymal." With regard to the classification of the MonticuHporoids, Dr Dybowski gives the following synoptical table of the divisions of the group which he proposes to adopt : — (I.) The corallum consists of tubular corallites. A. The walls of the corallites relatively thin and structureless. (i.) No " coenenchyma " {i.e.., interstitial tubes); the corallites in direct contact with one another. («) Tabulae present ; the corallites of comparatively considerable diameter. 1. Genus Dianiilites, Eichwald. (/') Tabulae wanting ; corallites capillary. 2. Genus Soknopora, Dyb. (2.) "Coenenchyma" (/.) Corallites of two different kinds ; thick-walled corallites alter- nating with thin-walled corallites. 9. Genus Eittopora, Dyb. (II.) The corallum consists of vertical rods, which are united with one another by a series of vesicles. 10. Genus Labcchia, E. and H. As I find myself unable to regard the above classification of the Monticuliporoids as in any way a natural one, and as nearly all the subdivisions proposed in it are, in my opinion, inad- missible, I shall here proceed to analyse the above groups in o-reater detail. The genus Dianulites, Eichw. (Dyb.) is defined by Dybow- ski {Joe. cit., p. 15) as including forms with a spherical, hemi- spherical, or botryoidal corallum, the surface being quite smooth or rarely exhibiting eminences. The corallites are more or less irregularly prismatic, of different sizes, the large and small ones irregularly mixed with one another. Tabulae are widely remote, not placed at corresponding levels in different indi- viduals. There is no " coenenchyma," and the corallites are in direct contact with one another. I have already (pp. 11, 12) given the reasons which would make me most unwilling to acquiesce in any attempt to revive the genus Dianulites, Eichw. These reasons seem to me to be so strong, that even if the above emended definition of Dy- bowski were found to embrace a natural group of Monticuli- GENERAL HISTORY. 21 poroids, I should still think it expedient to create a new name for the division. As it is, however, the forms included by Dybowski under the head of Diaimliies, Eichw., appear to me to be of different affinities, as regards some of them at any rate, while the asserted absence of a " coenenchyma " {i.e., of inter- stitial tubes) is certainly not true of them all. Thus, Monti- ctdipora petropolitana, Pand., included by Dybowski under the genus Diamilites, possesses a " coenenchyma " in the same sense that any Monticuliporoid can be said to do so — that is to say, it possesses a series of small interstitial corallites, which are per- ceptibly, if only slightly, more closely tabulate than is the case with the larcfe ones. That these interstitial corallites are fewer and more scattered than is usually the case in the Monticuli- poroids, does not alter their morphological significance, and would not justify us in excluding them from the category of what Dybowski calls " Ccenenchym." In addition to M. petro- politana, Pand., Dybowski places under Diaimlites, Eichw., seven species or varieties — viz., D. peti^opolitanus, van hcxa- porites^ Pand., D. apictilatus, Eichw., D. rhovibicus, Nich., D. eleganhihis, Fr. Schmidt, D. Haydenii, Dyb., and D. siilcatiis, Dyb. Not having seen any of the original examples upon which these species are founded, I can, of course, say little about them. Judging, however, from the descriptions and figures given by Dybowski, I should say \kvaX D . fastigiatus, Eichw. { = D. detri- tus, Eichw., according to Dybowski), is even nearer to the type of M. petj'opolitana, Pand., than the form to which Dy- bowski assigns the latter specific name. D. petropolitanus, var. Jicxaporitcs, Pand., would seem to be a separate species, and not a mere variety of M. petropolitana. D. apiculatiis, Eichw., is a peculiar type, which is more clearly dimorphic than is even the case in M. peti'opoiitana, Pand. The form termed D. rJwmbicus, Nich., is not sufficiently figured, but has nothing to do with the form which I described under the name of CJice- tetes rhovibicus, and which is really identical with the M. quad- rata of Rominger. The D. elegantuhts, Fr. Schmidt, has obviously no relation with any of the preceding. It, also, is 2 2 THE GENUS MONTICULIPORA. clearly dimorphic, and therefore possesses a " coenenchyma," in the sense in which Dybowski uses this term. The D. Hay- denii, Dyb., seems to belong to that section of the Monticuli- poroids to which I have given the name of Monotrypa. Lastly, the Dianulites sidcatus, Dyb,, differs radically from all the pre- ceding forms in the fact that it possesses perforated tahdce in the large corallites ; and it either belongs to Prasopora, Nich. and Eth. jun., as subsequently defined, or it is nearly allied to this. Upon the whole, therefore, I find it impossible to accept Dianulites, Eichw., as emended by Dybowski, as being a natural group, and I cannot agree with the suggestion made by Dr Steinmann (N. Jahrb. flir Min., 1880, p. 438) that this division ought to supplant Diplotrypa, Nich., or that it is in any way the equivalent of the latter. The genus Soieiiopora, Dyb,, is defined as including forms with an irregular spheroidal corallum. The corallites are pris- matic, and of very small diameter ; there is no " coenenchyma," and tabulae are wanting. The single species described under this head — viz., 6". spongioidcs {loc. cit., p. 124, PI. II. figs. i\a, I lb) — is said to have a smooth and shining surface, and to show no obvious calicine apertures. It seems tolerably certain that this form can have no relationship with the Monticuliporoids, though it is difficult to say anything positive as to its real affinities. I should rather be disposed to suggest that it may prove, on further examination, to be related to the singular type described by Mr R. Etheridge, jun., and myself under the name of Tctradiicm Pcachii (Ann. Nat. Hist. 1877, and Mon. Sil. Foss. Girvan, vol. i, p. 31, PI. I. fig. 3, and PL II. figs. \-\b). The third genus of Monticuliporoids in Dr Dybowski's arrangement is Callopora, Hall. It is unnecessary to discuss the characters ascribed by Dybowski to this genus, as the forms included under it are of quite different affinities, and as, moreover, there is at present no sufficient reason to doubt that Callopora, Hall, is a synonym oi Fistulipora, M'Coy, the latter GENERAL HISTORY. 23 having the priority (see Nicholson, Pal. Tab. Cor., p. 304). As to the forms included by Dybowski under the head of Callo- pora, Hall, the first is identified with the C. intminiforuiis of Hall, and a number of figures illustrative of its structure are given (PI. IV. figs. \-\k), from which it can be seen that at least two distinct species have been placed under the same name. Thus, it is certain that there can be no specific rela- tionship between forms like those represented in PI. IV. figs. \c and \b, where the large corallites are prismatic and have complete horizontal tabulce, and such as figs, i/and i/^ of the same plate, where the large corallites are circular and have inco7nplete cxcentrically perforated tabtdce. The former are certainly not Fistidiporcs, while the latter are undoubtedly referable to Prasopora, Nich. and Eth. jun., and are nearly allied to the form which I shall subsequently describe under the name ol P. Schvynii, Nich. As regards the other species referred by Dybowski to Cal- lopora, Hall, one — viz., C. maaUata, Dyb. — is an unquestion- able member of the genus Fistidipora, M'Coy (and is there- fore a Callopora) ; and C. hetcrosoleii, Keys., is probably sim- ilarly referable to Fistulipora. On the other hand, C. pyrifor- vds, Eichw., and C. ligid/onjus, Dyb., are almost certainly not referable to Fistulipora, M'Coy, and the last of these would seem to be a Diplotrypa. The fourth genus adopted by Dybowski is Trachypora, E. and H., to which is referred the single species T. porosa, Dyb. The form so named is an exceedingly remarkable one, and, if its structure were sufficiently worked out, would probably prove to be the type of a new genus. Be this as it may, it has nothing whatever to do with the genus Trachypora, E. and H., the latter being now known to belong to the Favositidce, and to be entirely destitute of a " ccenenchyma " (see Pal. Tab. Cor., p. 102). The fifth genus is Stellipora, Hall (Constcllaria, Dana), to which are referred two new species — viz., S. Revalensis, Dyb., and S, constellata, Dyb. With regard to these, it is sufficient 2 4 THE GENUS MONTICULIPORA. to say that there seems no reason to doubt the correctness of their reference to Constellaria. The sixth genus is Orbipora, Eichw. (emend, Dybowski), which is defined as comprising forms with a polymorphic cor- allum, composed of tubular corallites, the thickened and lam- ellar walls of which are amalgamated with one another. Scler- enchymatous structures of a string-like character (" Wand- strange") are developed in the walls of the corallites; and there may or may not be tabulae. The forms referred to it are O. distincta^ Eichw., O. fungiformis, Eichw. (this last not described), O. arborescejis, Dyb., and O. Paiidcri, Dyb. I have already given a brief account of Orbipora, Eichw. (p. 1 1), and need only add that the definition of the genus given by Dybowski, as indeed he himself admits, is in all essential points an entirely different one to that of its original author. I have also, already, in speaking of Dianulites, Eichw. (pp. ii, 12), given the reasons which render me, in liuiine, entirely opposed to all attempts to revive old generic names which were, to be- gin with, unrecognisably characterised ; and I consider these reasons to be just as powerful in this particular case as in the instance of Dianulites. I need only add, therefore, a few re- marks upon the species which Dybowski refers to Orbipora Eichw., so far as I have been able to study these without actual specimens. O. distincta, Eichw. {loc. cit., PI. II. figs. \oa, lob), is apparently a Monticuliporoid, with numerous abor- ted spiniform corallites (" Wandstrange "), greatly thickened walls, and no tabular. I am not acquainted with any form which very closely resembles this. O. arborescens, Dyb. (PI. II. figs. 8^:2;, 8^), is a Monticuliporoid which is very closely allied to M. hunida, Phill, of the Carboniferous rocks. On the other hand, O. Pandcri, Dyb., seems to be a true Steiio- pora, Lonsd., nearly allied to S. crinita, Lonsd. (of which I have examined typical specimens by means of thin sections), and, like it, not a normal type of the genus. The spine-like processes (" dornformige Vorsprlinge ") which Dybowski de- scribes and fiofures as seen in lonof sections of the corallites, GENERAL HISTORY. 25 seem to be really the cut edges of perforated and incomplete tabulae, such as are so characteristic of some types of Steno- pora, Lonsd. (see the long section of 6". Hozvsii, Nich,, fig. 12, b). The genus Monticulipora, D'Orb., in the restricted sense in which it is understood by Dybowski, is divided into two prim- ary sections. The first of these is defined as comprising poly- morphic coralla, with or without monticules (" Hugelchen") ; the corallites tubular, of different diameters, with thick, lamel- lar, amalgamated walls. No " Wandstrange " or " Wandrohr- chen " {i.e., aborted or perfect spiniform corallites) are present. Tabulae present. The forms included under this head are M. rugosa, E. and H., which is, in the main, rightly described and figured ; M. Wesenbeigiana, Dyb., which is very closely allied to the preceding ; and M. csdilis, Eichw., which is related to M. Treiitonensis, Nich. All these three forms belong to the section Heterotrypa as defined by me ; but Dr Dybowski has failed to recognise that the interstitial corallites are other than young tubes, and he has not observed that they have the structural peculiarity of being much more closely tabulate than is the case in the laro-e corallites. The absence of aborted or o perfect " spiniform corallites " (" Wandstrange " and " Wand- rohrchen"), upon which Dybowski relies in separating this section of Monticnlipora from the second, as also from Orbi- pora, Eichw., is, according to my views, a matter of no classi- ficatory value at all. The second section of Monticulipora, D'Orb., according to Dybowski, comprises forms quite like those just mentioned, except that they possess numerous " spiniform corallites " (" Porenkanalchen "). As just remarked, I attach no weight to this circumstance. The only form described under this section is one which Dybowski thinks to be possibly the so- called Chcetetcs lycopei'doii, Say ; and the figures and descrip- tions given of it show it to be allied to M. (^Heterotrypa) moii- i I if or mis, Nich. The eighth genus in Dybowski's classification is one which 26 . THE GENUS iMONTICULIPORA. he identifies with Trciuatopora, Hall. I am not aware that any of the original types ascribed by Hall to Treniatopora (Pal. N. Y., vol. ii. p. 149 ct scq) have as yet been investigated by means of modern methods, or that such Investigations, at any rate, have up to this date been made public. In the absence of this essential preliminary, it seems impossible to decide whether or not Treniatopora, Dyb., is identical with Tre7natopora, Hall. The forms included by Dybowski under this title appear, however, to constitute a peculiar group of Monticuliporoids, and I shall defer their more full considera- tion to an appendix at the end of this work. The ninth genus of Dybowski's system is one which is founded for the first time under the name of Ditfopora. This also appears, like the preceding, to embrace a peculiar group of Monticuliporoids ; and I shall similarly consider its characters in an appendix, as I am personally unacquainted with any types that I could refer to it. Finally, Dr Dybowski includes amongst the Monticulipor- oids the extraordinary genus Labcc/iia, E. and H. If, how- ever, this type really has any genetic relation with the Mon- ticuliporoids, as is very dubious, such relation cannot be a close one ; and the genus is certainly the representative of a special family (see Pal. Tab. Cor., p. 330). On the other hand, there is the high authority of Dr Steinmann (Ueber die fossile Hydrozoen aus der Familie der Coryniden : Palseontographica) in favour of the view that Labcchia, E. and H., truly belongs to the Hydractiniidc€. In 1877, a peculiar type of Monticuliporoid was described by Mr R. Etheridge, jun., and myself under the name of Prasopora (Ann. Nat. Hist., ser. 4, vol. xx. p. 38). 1S77 con- \Yg regarded this at first as a distinct oenus ; but I have since examined other allied types, and I am now disposed to regard it as a section or sub-genus of JMonti- culipora, D'Orb. Its distinctive characters will be fully treated of subsequently. GENERAL HISTORY. 27 In the summer of 1878, Mr U. P. James commenced the publication of a palseontological serial, entitled ' The Palaeon- tologist,' of which, so far as I know, only four num- bers appeared, the last being dated July 1879. In it were given short descriptions of various fossils, unfortunately not accompanied by any figures. Amongst these Mr James described the following new species of MonticiUipora (referring these to the genus Ch<^teles) : viz., C. ci'itsttilatus, C. Mceki, C. varians, C. szibrotuiidiLs, and C mimttus. I have no means of judging of the affinities of the three last of these ; but I have examined the two species first mentioned, both macroscopically and microscopically. The first of these i^M.? criistulata, James) is certainly a new form, but I am not prepared to assert posi- tively that it is a Monticiilipora, as it has some curious points of resemblance to some of the types which are usually placed under the genus Ceramopora, Hall. Of the latter, of which I have ample material, I am able to say that the name of M. Mceki, which Mr James only proposed provisionally, must be abandoned, as it is a mere variety of the previously described AI. gracilis, James. In 1878, Mr E. O. Ulrich published (Journ. Cincinnati Soc. Nat. Hist., PI. IV. figs. 7, 7^) a description of a new species of Alonticulipora, under the name of Chcstctes vemistus. In the following year (1879) the same excellent observer pub- lished two further papers in the same Journal, in which various species of Montictdipora and allied types were described. In the first of these {loc. cii., PI. VII. figs. 25, 25^), the author described a new species of MouticiLlipora under the name of Chcctctes cojupressus, but the form is one with which I am unacquainted. In the second paper in question (PI. XII. figs. 9-12), entitled " Description of a New Genus and some New Species of Bryozoans from the Cincinnati Group," Mr Ulrich described as new species of Monticulipot'-a the follow- ing types (placed under Chcctcics) : C. granuli/erus, C. irregu- laris, C. sttbglobosus, and C. clcgaus. With regard to the first 2 8 THE GENUS MONTICULIPORA. of these the author observes that it is distinguished by the possession of thick strongly granulated " intercellular spaces ; " and he adds that, " when slightly worn, the granules or spines are seen to be simply surface-extensions of curiously modified minute tubuli." This, so far as I know, is the first clear recognition of the singular "spiniform corallites " of so many of the Monticuliporcu ; since Dybowski seems to regard his " Wandrohrchen " and " Wandstrange " as mere accessory structures. The author, moreover, refers Alonticidipora {Chce- tetes) Oj^toni, Nich,, to a new genus of Poiyzoa, which he names Atactopora, and of which he supplies descriptions of several new species, with which I am not acquainted. So far as M. ? Ortoni, mihi, is concerned, I shall afterwards give reasons for thinking that it will be difficult, with our present knowledge, to separate it definitely from Monticulipora, with some species of which it shows remarkable affinities, at the same time that it has equally singular features of its own. I fail, at any rate, to recognise in it the fundamental feature which Mr Ulrich considers to separate his genus Atactopora from Monticulipora, D'Orb. — namely, the presence of pseudo- septa. Towards the close of 1879 I published a work on ' The Structure and Affinities of the " Tabulate Corals" of the Palae- ozoic Period,' in which I gave a general account of the struc- ture, development, and systematic position of Monticulipora and various allied types. I also submitted a provisional classi- fication of the forms included usually under the comprehensive genus Monticulipora, and I gave an account of the structure of typical examples of some of the more striking and characteristic forms of the group. I need not give any analysis of the above work, since the bulk of that portion of it which dealt with MontictUipora is incorporated, with great additions, and with some alterations, in the present treatise. Lastly, in 1880, Mr E. O. Ulrich published a list of the species of ]\Iontictilipora and allied genera known to him as GENERAL HISTORY. 29 occurring in the Cincinnati Group of Ohio (Cat. Foss. Cin- cinn. Group of Ohio, Indiana, and Kentucky). In this catalogue a number of new species are named ; but as the names are not accompanied with any descrip- tions or figures, they have, of course, in the meanwhile no actual validity. 3° CHAPTER II. THE GENERAL AND COMPARATIVE STRUCTURE OF MONTICULIPORA. The genus Moiiticulipora, D'Orb., using this name in its wide sense, comprises a large number of Palaeozoic fossils, which range from the Lower Silurian to the Carboniferous, inclusive. They attain their maximum in point of development, both as regards species and individuals, towards the middle or end of the Lower Silurian period, being much less abundant in the Upper Silurian, and still less numerous in the Devonian and Carboniferous deposits. Species of the genus have been stated to occur in the Permian rocks, but I am not aware that this observation rests upon microscopic examination. As regards its generic^ characters, Monticulipora, D'Orb., may be defined as including forms in which the corallum is composed of numerous closely approximated tubular corallites, the walls of which are never absolutely amalgamated with one another, though sometimes seemingly so. Walls of the coral- lites imperforate. Septa entirely wanting. Tabulae always present in greater or less number, though sometimes nearly 1 In the following definition, the name of Monttculipora is used in its widest sense, as embracing all the types known to palaeontologists as Mo7iticulipora, Fis- tulipora, Dekayta, and Constellaria. As will be afterwards shown, these types agree with one another so closely that they can be readily included under a common definition ; and they therefore form a natural genus. At the same time, it is very inconvenient, as a matter of practice, to include many sub-genera under a single genus; and I shall therefore treat Fisfitlipora, M'Coy, Constellaria, Hall, and Dckayia, E. and H., as if they were so many distinct genera, though their distinc- tive structural features would not seem to be of sufficient importance to warrant our regarding them in actual fact as more than mere sub-genera di Mfl7iiiciilipora. GENERAL AND COMPARATIVE STRUCTURE. 31 obsolete; generally " complete," and approximately horizontal ; sometimes, in a peculiarly modified manner, " incomplete." Corallites usually divisible into two distinct groups, one of large and the other of small tubes, the latter being usually, but not always, more closely tabulate than the large tubes, or show- ing other peculiarities of structure. Surface often, but not always, exhibiting at regular intervals definite areas which are occupied by corallites which are either larger or smaller than the average. These areas may be elevated above the general surface, when they are called " monticules ; " or they may be level with the surface, or slightly depressed below it, when they are called " maculae." They^r;;^ of the corallum is extremely variable, though often tolerably, or even altogether, constant for the same species ; the massive, discoid, dendroid, laminar or frondescent, and encrusting types of corallum constituting those most commonly met with. The arrangement of the tubes which make up the skeleton of a Montiadipora necessarily varies with the form of the corallum, and the chief variations in this respect will be noticed immediately. There is, however, one character which has such an important practical bearing that it deserves to be noticed in this place. In many Monticuliporoids, namely, though not in all, the tubes which constitute the colony become specially modified in structure as they pass into their final stage of growth, and approach near to the surface. Thus it is very common to find that the corallites in the centre of the corallum are thin-walled, and nearly or quite free from tabulee, whereas in the outer portion of their course, near the surface, their walls become thickened, and tabuloe are abundantly developed. Moreover, it is very usual to find that the colony contains elements, such as small corallites or specially modified tubules, which in general do not extend downwards into the deeper parts of the corallum, but which are only developed in a zone immediately below the actual surface. Hence, in most ordinary types of Monticulipora, such as the great majority of the den- 32 ■ THE GENUS MONTICULIPORA. droid species, the corallum may be readily differentiated into two distinct regions, an axial ?i.\\6. a peripheral region. In the axial region the corallites are generally thin-walled and angular, often with few tabulae. On the other hand, in the peripheral region, the corallites are often thick-walled, commonly rounded in shape, and usually with many tabulae ; while it is in this region that we meet with " interstitial tubes " and " spiniform corallites," if these structures are present at all. There are, however, a few types in which the corallum does not exhibit this differentiation into a deep and a superficial region. The relations of these two regions to one another when developed at all, necessarily varies with the form of the corallum. The commonest arrangement is that found in the dendroid species of Montienlipora, where the axial region of the corallum is truly axial, and forms a central fasciculus of nearly vertical thin-walled tubes ; while the peripheral region forms a thicker or thinner investment to the median axis, and is composed of the tubes of the latter as they become bent and curved out- wards at varying angles in order to reach the surface. It is most important to remember this common difference in the characters of the axial and cortical portions of the corallum in the Monticuliporoids, because it is impossible otherwise to prepare thin sections of such forms which will give any adequate or correct idea of their structure. If, for example, we take any dendroid type of the genus, where the corallum is composed of an axis of nearly vertical tubes, and a cortical region composed of the same tubes bent at all angles up to 90" from the vertical, it will be at once obvious what sections it is necessary to make, and also what any given section will show us. Thus a longi- tudinal or vertical section, taken through the median plane of the corallum, will give us a vertical section of the tubes of the axis, and will also divide longitudinally the outwardly-bent and curved tubes of the cortical portion. On the other hand, a genuine transverse section, taken at right angles to the long axis of the corallum, will give us a true cross-section of the corallites in their axial region, where they are nearly vertical ; GENERAL AND COMPARATIVE STRUCTURE. 33 but it will give us an obliquely longitudinal section of the coral- lites in the peripheral region of the corallum, where they are bent at greater or less angles away from the vertical. Neither of the above sections, therefore, would give us a cross-section of the tubes in their peripheral region, where they have attained their adult characters, and where it^ is, above all, important to be able to investigate them. In order to obtain what is wanted, it is necessary to make a third section which shall run along a plane parallel with the sin'face, and Just a little belozv it. Such sections we may call tangential, and they are absolutely indispensable to any understanding of the true characters of the great majority of the Monticuliporoids. The precise direction in which it will be necessary to cut any given specimen in order to obtain cross-sections of the tubes in their final and fully developed condition, will necessarily vary with the form of the specimen ; but in all instances the require- ments of the case will be met by sections taken in a direction tangential to the calicular surface, and just below that surface. Moreover, the nearer to the actual surface is the plane of such a section, the greater is the probability of its fully revealing the adult characters of the tubes. We may now pass on to consider in greater detail the general and comparative structure of the Monticuliporoids, with special reference to those points which require to be particularly studied in the determination of the different types of this large and variable group. I. Forin of the Corallum. — In the first place, as regards the mode of growth of the corallum, and the form ultimately assumed by the colony, we find, as before remarked, great variations, and we are obliged to conclude that the mere ex- ternal shape of the corallum is a character of no classificatory value. It is not that individual species are specially variable in shape, for many types exhibit a tolerably constant form when adult ; but it is the fact that so many structurally diverse species assume the same shape, that robs this feature of any special value that it might otherwise possess. Admitting, c 34 THE GENUS MONTICULIFORA. however, the comparatively trivial weight which can be at- tached to the mere external shape, we find that the coralla of the Monticuliporoids usually exhibit one or other of the following conditions : — {a) The simply massive corallum, which is attached by one point at its base, and may be more or less spherical or glob- ose in form, or sometimes largely lobate. No epitheca is apparently developed in such types, and occasionally {e.g., M. irregiUaris, Ulrich) no basal point of attachment exists (the corallum in some of these cases having grown round the stem of a Crinoid). The simply massive corallum is seen in M. tindtdaia, Nich., and occurs as a variation in some normally laminar types {e.g., M. molesta, Nich.) {b) The discoid corallum, which has the form of a plano- convex or concavo-convex disc, the upper surface of which is occupied by the calices, while the lower surface is covered by a striated and wrinkled epitheca, and may either be nearly flat, or may be more or less deeply concave. In these cases there is every reason to believe that the corallum was free. This form of corallum is one very common among the Monticulipo- roids, and is exhibited by various types which have no rela- tionships in their internal structure. Thus, it is characteristic Q)i M. petropolitana, Pand,, yJ/, Winteri, Wich., AI. petasi/ormis, Nich., Af. .Selwyiiii, Nich., AI. Wkiteavesii, Nich., Prasopora GraycE, Nich. and Eth. jun,, and some forms of Fistulipora, in all of which the corallum, with some subordinate modifica- tions, is of a proportionately considerable height as compared with its width. The same type of skeleton occurs constantly in Al. discoidea, James, AI. calyada, James, and AI. Newberryi, Nich.; but in these cases the height of the corallum is greatly reduced, so that it becomes more or less leaf-like. {c) The dendroid or ramose corallum, which consists ot cylindrical or subcylindrical stems, which branch more or less extensively, the base being attached to some foreign object, and the entire free surface being covered by the calices. More or less striking modifications of this type may occur by GENERAL AND COMPARATIVE STRUCTURE. 35 the great fattening of the branches, by their becoming palmate, or by their mutual anastomosis ; and in one form (yJ/. briarca, Nich.) there is no evidence that the base was fixed to a foreign body. The dendroid form of corallum may, however, be re- garded as the commonest of all the types of figure assumed by the Monticuliporoids ; and it is exhibited by M. 7'amosa, D'Orb., M.pidchclla, E. and H., M. hmiida, Phill., M. gracilis, James, AI. Andrewsii, Nich., M. Jaincsi, Nich,, and very many other species, the internal structure of these bearing no relation at all to their externally similar shape. {d) The laminai^ or frondescent form of corallum, which consists of a more or less widely expanded and laterally compressed frond, which is rooted at its base, and has its entire free surface covered with the calices. The corallum in such cases consists of two strata of corallites, which are placed back to back, so to speak, and diverge from a central plane to opeii on the two opposed surfaces of the frond. The central plane of the corallum may be marked merely by an irregular cellular layer, or by an apparently definite, more or less com- plete calcareous lamina, or more rarely {M. Dawsoni, Nich.) the corallites are vertical in the median line of the expansion, and simply diverge outwards as they grow upwards. The forms of this type are usually constant in certain species, though occasionally (as in M. molesta, Nich.) a normally lami- nar species may assume a massive mode of growth. The spe- cies which possess a frondescent corallum are M. luaiunnUata, D'Orb., M. frondosa, D'Orb., AT. vwlesta, Nich., M. pavonia, D'Orb., and M. Dazvsoni^ Nich. ; and it is noticeable that while the form of the corallum is in these species remark- ably similar, no two of them are at all closely related in their internal structure. {e) The encrusting corallum, in which the colony consists of very short corallites, forming a thin crust, which is parasitically attached by the whole of the under surface to foreign objects. The Monticuliporoids of this type are more like the ordinary encrusting Polyzoa than are any others of the group ; and some 36 THE GENUS MONTICULIPORA. forms which have been placed here are very probably really Polyzoa, and not referable to Montimlipora at all. Others, however, resemble the more normal types of the group in their internal structure ; and I do not at present see how they can be definitely separated from the present genus. Among these I may mention M. Cincinnatiensis, James, M. ttcberculata, E. and H., M. crustulata^ James, and probably M. Ortoni, Nich., all of which I have examined by means of thin sections, and most of which will be subsequently described in detail. {/) As a modification of the preceding may be mentioned certain types which consist of moderately but not excessively short corallites, forming a crust which is apparently invariably attached to some particular class of foreign bodies, and which, in consequence, acquires an apparently constant form. As a good example of this group, we may take the curious M. clavacoidea, James. II. The Strztcture of the Walls of the Corallites. — Much more important, from a zoological point of view, than the mere form of the corallum, is the minute structure of the wall of the tubes ; and in this respect the Monticuliporoids show wide dif- ferences. The corallites of Moiitinilipora, whatever their form may be, are always contiguous throughout their entire length ; and, theoretically, each tube possesses a perfectly independent and complete wall. In some cases this theoretic and un- doubtedly primitive independence of the calcareous investment of each individual tube is obviously and clearly preserved throughout the entire growth of the corallum. Hence, in thin tangential or longitudinal sections of such forms, the vis- ceral chamber of each corallite is seen to be surrounded by its own investment of light-coloured sclerenchyma, and to be separ- ated from the corresponding investment of all the tubes in immediate contiguity with it by a clearly-marked dark line, which is often thickened into larger or smaller nodes at the angles of junction of the corallites. This permanent preserva- tion of the primitively duplex structure of the wall separating adjoining visceral chambers is seen in many forms, such as GENERAL AND COMPARATIVE STRUCTURE. 37 M. pitlchella, E. and H. (fig. i, c), M. petasiforjnis, Nich. (fig. 2, b), M. Girvanensis, Nich., M. Treiitonensis, Nich., M. Jamesi, Nich., &c. The actual thickness of the proper wall of each tube, internal to the dark boundary-line which marks the primordial wall, is very variable, being exceedingly limited Fig. I. — A, Tangential section of a few corallites of the typical MonticuUpora petropolitaiia, Pand., from the Lower Silurian of Sweden ; B, Tangential section of a corallite of a typi- cal example of Montkidipora ramosa, E. and H., from the Cincinnati group of Ohio ; c, Tangential section of a corallite of a typical example of Montiailipora pulchclla, E. and H., from the Wenlock Limestone of Dudley ; D, Tangential section of a corallite of the typi- cal Chcvtetes radians, Pand., of the Carboniferous rocks of Russia. All the sections are taken just below the calices : A, B, and C are enlarged fifty times ; D enlarged twenty- five times. in forms like M. petasiforviis, Nich. (fig. 2, b), while it is more extensive in forms like M. pulchella, E. and H., and is some- times exceptionally great, as in types like M. Treitionensis, Nich. The internal secondary wall also is usually, though not always, rounded off internally, so as to give the whole tube a circular or oval aspect, while the thin line of the original wall is almost always markedly polygonal. In another group of Montiailipo7'a;, represented by forms 38 THE GENUS MONTICULIPORA. like M. petropolitana, Pand. (fig. i, a), and M. tindulata, Nich. (fig. 2, a), the walls are so thin that the partitions between the Fig. 2. — A, Tangential section of a single corallite of Monticulipora tindulata, Nich.; F, Tan- gential section of a single corallite of Monticulipora petasiformis, Nich., showing the duplex character of the wall ; C, Tangential section of a corallite oi Moniiailipora ritgosn, Edw. and Haimes ; D, Tangential section of a corallite of Alonticitlipora Aininnvsii, Nich. All the sections are enlarged fifty times. visceral chambers of contiguous corallites appear to be abso- lutely indivisible and without structure, presenting themselves in thin sections merely as delicate dark lines. Dybowski (Die Chsetetiden) lays great stress upon this feature, and uses it as a basis for subdividing the Monticuliporoids into two primary sections. For my own part, I believe that in such a complex group as the present, no single character, such as this is, is of itself sufficient for the establishment of primary subdivisions ; and I feel satisfied that this apparent amalgamation of the walls of contiguous corallites must be due to our imperfect methods of observation. That this is the case seems suffi- ciently proved by the consideration — which I shall have to speak of again — that even in forms like these (viz., HI. lui- didata, Nich.), rough fractures will demonstrate what thin sections fail to show — namely, that the apparently structureless wall is really double. In rough fractures, that is to say, we find that the corallites always separate cleanly from one an- GENERAL AND COMPARATIVE STRUCTURE. 39 Other, each carrying with it its own wall, a phenomenon which could not be possible if the primitively duplex condition of the walls of adjoining tubes had in reality been destroyed. In a third group of cases, embracing many of the most typi- cal members of the group, such as M. ramosa, E. and H. (fig. I, b), M. rugosa, E. and H. (fig. 2, c), M. G Ncalli, James, M. nodtdosa, Nich., &c., there is no dark line running in the centre of the partition between contiguous tubes ; and the walls thus at first sight appear to be amalgamated, as they actually are in ChcEtetes proper. In these cases, however (figs, i, b, and 2, c), the state of matters really differs widely from that which exists in Chcetetes, Fischer, since each visceral chamber is en- closed by a distinct dark line or marginal ring, usually circular or oval in outline, marking the original boundary of the tube, and the interspaces between these dark lines are filled in by sclerenchyma of a different texture and much lighter colour. In these cases, therefore, it would appear that the corallites are not only primitively distinct, but that in approaching the surface they do not touch each other at all to begin with, or only to a very limited extent, the ultimate union of the coral- lites being effected by means of a secondary deposit of calcar- eous matter. In such forms as these, therefore, the corallites in the deeper parts of the corallum are thin-walled, closely con- tiguous, and more or less polygonal ; whereas they become much thickened and more conspicuously circular or oval in shape as their mouths are approached. The structure of the wall is, in fact, very similar in these cases to what is observable in Stenopora, Lonsd., except that the thickening of the tubes is uniform, and is not confined to the production of periodic rings. In other cases, again, the apparent amalgamation of the cor- allites is carried still further, since the various visceral chambers are bounded by well-marked lines, and the space between these is simply filled with light-coloured sclerenchyma, which usually exhibits fine concentric laminse of deposition in the immediate neighbourhood of the actual tube-cavity, but seems to be abso- lutely structureless just at that central point where we should 40 THE GENUS MONTICULIPORA. expect to find traces of the original boundaries between the coralHtes. This state of parts occurs in forms like M. tumida^ Phill., M, Andrezvsii, Nich. (fig. 2, d), M. gracilis, James, M. moniliformis, Nich., and various other allied types. Some forms of Monticuliporoids show peculiarities in the structure of the wall slightly different to any of those alluded to above, but the preceding are the most important types with which we have to deal ; and our knowledge on this subject, as derived from tangential sections, may be corroborated, and in some points supplemented, by an examination of longitudinal sections. In these we see the same great apparent differences that have been noted in tangential sections. Thus, in some Fig. 3. — A, Long section of the corallites o{ Moilkulipora Ulrkhii, Nich., showing the struc- ture of the wall close to the surface, as well as the "spiniform corallites ; " B, Long sec- tion of two corallites of Montkidipora monilifoniiis, Nich., also close to the surface, showing the thickened wall and the hollow spines ; C, Long section of two corallites of I\Icmticiih'pora petropolitana, Pand. ; D, Long section of the corallites of M. tituUilata, Nich. All the sections are enlarged fifty times. forms, like M. petropolitana, Pand., and J/, tuidulata, Nich. (fig- 3. c and d), the walls separating adjoining corallites appear as seemingly structureless, thin, and delicate dark lines, without GENERAL AND COMPARATIVE STRUCTURE. 41 any trace of their originally duplex nature. In all cases, more- over, whatever may be the structure of the walls of the tubes in their final and most developed condition, the corallites co7n- mence with thin and apparently indivisible walls. Hence, in the axial and deeper regions of any Monticuliporoid, long sections always exhibit the thin and seemingly structureless walls which exist throughout the entire length of the tubes in forms like M. petropolitana, Pand. ; and this feature is equally shown by transverse sections. In very many Monticuliporoids, however, the walls of the corallites in their peripheral and more superficial portions become more or less extensively thickened by a secondary deposit of sclerenchyma. In some of these cases — as, for example, in M. pulchella, E. and H, — the original walls of the tubes can still be clearly recognised, traversing the centre of the light-coloured secondary sclerenchyma as so many thin dark lines. In other cases, as in forms like M. ttuuida, Phill., M. Ulrichii, Nich. (fig. 3, a), M. inoniliformis, Nich. (fig. 3, b), and many others, the original lines of demarcation between adjoining tubes can be only indistinctly or not at all made out, and the corallites seem to be indistinguishably amalgamated. In such cases, lonoritudinal sections o'ive us a clearer idea of the mode of formation of the thickened wall than we obtain from tangential sections. In such cases, namely, the longitud- inal section of the wall (fig. 3, a and b) shows that it is com- posed of a succession of superimposed conical layers of scleren- chyma, which are deposited one above the other as the growing margin of the wall is carried upwards. The growth of the thickened wall is not, therefore, effected by the deposition of a new layer of sclerenchyma along the entire interior aspect of the already existing tube-cavity, but is carried on simply by the successive formation of new laminae of calcareous matter at the margin of the old calice. The structure of the wall, therefore, is in these cases precisely similar to what is found in Steno- pora, Lonsd., except that the production of new layers of scler- enchyma appears to take place continuously and regularly, 42 THE GENUS MONTICULfPORA. instead of periodically, so that the wall becomes uniformly thickened, instead of exhibiting alternate dilatations and con- tractions. Apart, however, from the evidence of microscopic sections, which I have sufficiently discussed above, there is sufficient evidence from other sources that the tubes of Monticulipora never become absolutely amalgamated with one another, as they do in CJicetetes, Fischer (fig. i, d). In discussing the minute characters of various species of JMoiiticiilipora in the subsequent chapters of this work, I may speak of the tubes as being fused together, or as having their walls amalgamated ; but in so doing, I must be understood simply as referring to the apparent fusion exhibited by microscopic sections. That this fusion is not real, but that the walls, even in such species as M. 2indulata, Nich., and AI. pctropolitana, Pand., remain really permanently distinct, seems to be incontrovertibly shown by the fact that fractured surfaces, so far as I have seen, in- variably exhibit the exterior of the tubes. This was long ago noticed by Lonsdale, and was set down by him to the fact that the corallum of JMojiticiilipora increased by gemmation, whereas that of Chcetetes produced new tubes by a process of fission. In the latter, therefore, rough fractures exhibit the interior of the corallites. Of the correctness of Lons- dale's observations on this point — as observations — I can entertain no doubt ; but I am not clear that the phenomena are really due to the cause which he assigns. That C/icetetes increases fissiparously is certain ; but I am not sure that gem- mation is the regular or exclusive mode of growth amongst the Monticulipom. I have formerly expressed the opinion (Ann. Nat. Hist., sen 4, vol. xviii. p. 86) that certain species of Monticulipora exhibited fissiparous growth ; and though further observations have shown me that I relied upon evi- dence which admitted of misconstruction, and that gemma- tion is the common mode of increase in the Monticuliporcr, I am still inclined to think that the phenomena manifested by thin sections show that fission of the old tubes occurs at times GENERAL AND COMPARATIVE STRUCTURE. 43 as well. At any rate, I feel sure that the difficulty of deter- mining this point in the case of the smaller species is so great that I am right in the formerly expressed opinion that this character alone should not be accepted as an adequate generic distinction between ChcEtetes and Monticulipora (Quart. Journ. Geol. Soc, vol. XXX. p. 500). We have at present no evidence as to the existence of " mural pores " in any species of MontiaUipora ; and there is every reason to believe that the walls are really imperforate. So many species of the genus, at any rate, have now been exa- mined by means of thin sections, that it seems very unlikely that mural pores should have escaped notice, had such aper- tures in the walls really existed. This, therefore, is a point upon which the purely negative evidence may be legitimately accepted as of great weight. At the same time, there are some considerations which preclude our regarding the imperforate condition of the walls of the Monticuliporce as a point settled absolutely beyond dispute or doubt. Thus, we find species of the singular genus Stcnopora, Lonsd., in which mural pores can be certainly shown to be present, so that we can hardly suppose any member of the same genus to be without them ; and yet there are well-marked species of Stenopora in which the closest microscopic examination has hitherto failed to reveal the existence of any apertures in the walls. There are also forms (such as Favosites Bowerbanki, E. and H. sp.) which have all the general aspect and structure of the Monticuli- poroids, and which can only be separated from Monticulipora upon the ground that they are known to possess minute mural pores. Upon the whole, therefore, while I think the imper- forate condition of the walls of the Monticuliporoids to be as certain as anything established by merely negative evidence can be, I am not prepared to assert absolutely that mural pores are totally wanting. It is certain, however, that if mural pores do exist in the Monticuliporoids, they must be much more minute, and much more irregular in their distribution, than is the case with these openings in the typical Favositidcc. 44 THE GENUS MONriCULIPORA. III. Surface-chai'actcrs. — As regards the surface-characters of the MonticuHporoids, the appearances presented by the caHces vary according as we have to deal with a form in which the walls of the corallites remain permanently more or less thin throughout their entire extent, or with one in which the tubes underoTQ a marked thickenino- before reachinor the surface. In the former of these cases the calices are polygonal and sharp-edged, and thus resemble the calices in a Favosites of normal type. In the second case, the calices are rounded, oval, or subpolygonal, and exhibit thick and rounded margins — reminding us, so far as this particular character goes, of the calices of a Pachypora or a Stenopora. Monticulipora petro- poliiaua, Pand., and its allies, may be taken as exemplifying the former condition; while M. ramosa, D'Orb., J/, maimnu- lata, D'Orb., M. frondosa, D'Orb., M. Jamesi, Nich., M, tumida, Phill., and many others, are examples of the latter state of parts. Apart, however, from the mere characters of the calices, there are certain special superficial features present in various Mon- ticuliporoids, either singly or in combination, which demand special consideration. Foremost amongst these are the struc- tures which are known as " monticules" or " mamelons," from the presence of which, in many species, the name of Monticu- lipora is derived. The " monticules," in their most typical form, are circumscribed areas on the surface of the corallum, which are more or less elevated above the general level, so as to constitute a series of rounded, oval, or elongated eminences. Sometimes the "monticules" are composed of corallites which differ in no conspicuous feature from those which form the mass of the corallum {e.g., in AI. rainosa, D'Orb., and AI. Cin- cin7iaticnsis, James), and it is generally in such cases that these eminences are most conspicuous and prominent. In other cases {e.g., M. pidchella, E. and H.), the corallites which form the " monticules " are markedly larger than the average ; but in such cases the monticules hardly deserve the name, as they are scarcely or not at all elevated above the general surface. GENERAL AND COMPARATIVE STRUCTURE. 45 In other cases, in place of proper " monticules," we find other small areas which are occupied by corallites considerably smaller than the average, and which are either level with the general surface, or are even slightly depressed below it (as, for example, in M. frondosa, D'Orb., and M. siLbpulchella, Nich.) Such areas are usually called " macul£e," and they often exhibit a peculiar appearance, seemingly due to the closure of the mouths of their constituent tubes by a delicate calcareous membrane. IV. Spiniform Corallites, — Another very remarkable super- ficial feature which is specially common in the thick-walled species, though occasionally present in the thin-walled types, and which is also generally present in the genus Stenopora, Lonsd., is the existence of peculiar blunt spine-like structures, which are placed, in greater or less numbers, round the calices, usually at the angles of union of the corallites. Various Mon- ticuliporoid Palaeozoic corals have been noticed by different observers to possess these calicine spines ; and Milne-Edwards and Haime at one time (Brit. Foss. Cor. Intr., p. Ixi) regarded the existence of these structures as diagnostic of the genus Stejtopora as defined by them. Structures of this nature are, however, possessed by a large number of true Monticuliporce, and notably by M. frondosa, D'Orb., M. tumida, Phill., M. Jamcsi, Nich., AI. vwiiiliformis, Nich. (fig. 5), M. implicata, Ulrich (fig. 4), M. gracilis, James, and other forms. As viewed from the surface, these spines present themselves simply as so many blunt projections, which do not seem, so far as I have been able to observe, to be ordinarily perforated by any apical apertures. I have however, in some cases, detected minute circular apertures at the summits of these spines ; and it is quite possible that they are really generally present, but that they are filled up by the matrix or by infiltrated calcite. On the other hand, when examined by means of thin sections, these spines are found to be in no way of the nature of mere superficial ornaments, but they extend into the substance of the corallum, between the ordinary corallites, to a depth equal 46 THE GENUS MONTICULIPORA. to that reached by the smaller tubes of the colony. Tangen- tial sections taken a little below the surface (figs. 4 and 5) show that these apparent spines are composed of concentrically laminated sclerenchyma, exhibiting in their centre a dark circular spot or a clear circular space. There cannot, there- Fig. 4. — Portion of a tangential section of Monticulipora implkata, Uliich, showing the hollow intracalicine spines, enlarged fifty times. From the Cincinnati Group of Ohio. Fig. 5. — Portion of a tangential section of Alonticiilipora nionilifo7-mis, Nich., show- ing the intracalicine spines, enlarged fifty times. From the Hamilton Group of Ontario. fore, be any doubt but that these structures are primitively hollow, though their central cavities often appear to become filled up by a secondary deposit of sclerenchyma, as growth proceeds. In this primordial hollowness of the spines is to be found, I believe, the real clue to their nature ; and I can hardly doubt that instead of being merely appendages of the corallum, they are truly of the nature of peculiarly modified zooids or cor- allites.^ The correctness of this view is most readily recognised when we come to examine thin sections of those forms which ^ These peculiar hollow spines have been described and accurately figured in various Monticuliporoids by Dybowski (Die Chsetetiden, p. 9, &c.), under the name of " Wandrohrchen " or " Porenkanalchen." He regards them as of the same nature as the peculiar canals (" intramural canals") which are found in various "Tabulate corals" (such as Colnmnopora, Lyopora, Pleiirodictywn, &c.) The "intramural canals" of forms such as those above mentioned are, however, not bounded by distinct proper walls of their own, and are quite irregular in their dis- tribution. For these reasons, amongst others, I cannot regard them as being in any way comparable with the " spiniform corallites" of the Monticuliporoids, and I must in the meanwhile adhere to the views expressed in the text as to the nature of these latter structures. GENERAL AND COMPARATIVE STRUCTURE. a1 have usually been separated from Monticulipora under the generic title of Dekayia, E. and H. In these cases the sup- posed spines are very much reduced in number, but they are quite exceptionally developed, and they constitute the well- known surface-projections which are characteristic of the genus. These surface -projections certainly seem to be imperforate at their apices, but thin sections demonstrate conclusively that they are hollow internally, and that they only differ from the ordinary corallites in the greater thickness and density of their walls and the apparent general absence of tabulee. I do not myself entertain any doubt as to these being a peculiar form of corallites — doubtless tenanted in life by peculiar zooids — the mouths of which became closed by secondary deposit as the corallum assumed its final characters. Nor have I any doubt that the spines of forms like M. moniliformis, Nich. (fig. 5), M. Jamesi, Nich., M. tumida, Phill., M. gracilis, James, and others, are similarly peculiarly modified corallites, the mouths of which commonly become finally closed. A further evidence of this is to be found in such species as M. frondosa^ D'Orb., in which the spines do not necessarily appear as spines upon the surface, though thin sections exhibit appearances precisely similar to what has been indicated as occurring in the forms alluded to above. On the contrary, the spines often remain permanently open, and appear on the surface as minute thick- ened apertures between the ordinary calices, so that they have been both recognised and figured as a special group of corallites (Ann. and Mag. Nat. Hist., sen 4, vol. xviii. p. 92, PI. V. fig. 1 1). It is not, of course, essential that we should suppose these singular structures to be occupied by polypes ; but I think them to be modified zooids in the same sense as is true of the *' avicularia " of the Polyzoa, and I shall therefore speak of them as " spiniform corallites." In most cases, the central cavities of the " spiniform coral- lites" are easily recognisable in thin sections. In other in- stances, however, especially in cases where these structures are developed in great numbers {e.g., in M. tumida, Phill., PI. III. 48 THE GENUS MONTICULIPORA. fig. \d), many of the spines become so far aborted that their central cavities are no longfer to be detected, while others attain their full development. These aborted " spiniform corallites " appear to be in general what Dybowski has called '* Wandstrange," though he has apparently included other structures as well under this name. As these aborted spines appear, however, in forms of very different affinities (such as M. tumida, Phill., and AL Girvanensis, Nich.), it seems clear that they are of no classificatory weight, whatever view we may take as to their real nature. Lastly, if we admit the probable correctness of the views here advanced, we have a very interesting analogy established between certain forms of Monticulipora and some of the spe- cies of Stenopora, Lonsd., in which structures of a precisely similar nature occur. Thus, if we examine a tangential section of Stenopora Tasmattiensis, Lonsd., taken just below the sur- face (fig. 6), we see that the surface-spines are continued in- Fig. 6. — A, Vertical section of a few of the corallites of Stenopora Tasmaniensis, Lonsd., in the final portion of their course, enlarged twenty times, showing the annular thickenings of the tubes and the remote tabula ; B, Tangential section of the same, taken just below the surface, similarly enlarged, showing the transversely divided spiniform corallites be- tween the ordinary tubes. Carboniferous, Australia. wards precisely as they are in Monticulipora monili/oi'mis and allied types, while they are similarly composed of concentric- GENERAL AND COMPARATIVE STRUCTURE. 49 ally disposed lamellae of dense sclerenchyma. The central cavities of the spines seem, however, to be more or less com- pletely obliterated with age ; and the corallites in the outer portion of their course (fig. 6) exhibit the annular thickenings of their walls which are so characteristic of the genus Stenopora. In spite of these differences, the resemblance between the spines of the Monticuliporcs above alluded to and the similar structures in certain species of Stenopora is so striking that one can hardly resist the conviction that there must subsist be- tween the two a relationship of real affinity. V. Dimoiphisin of the Coralhim. — Apart, however, from the very curious structures that I have just spoken of under the name of *' spiniform corallites," microscopic examination brings out very clearly the important fact that the corallum in Monticidipora is in general dimorphic, and consists of two different sets of corallites, which must, during life, have been inhabited by different sets ofzooids. The existence of minute tubes, either scattered among the larger ones, or aggregated into special groups, has, of course, been long known to palaeontolo- gists ; but these have, for the most part, been regarded either as merely young corallites or as " coenenchymal tubuli." ^ Simi- larly, palaeontologists have long known that certain species of Monticidipora {e.g., M. pnlchelia, E. and H.) exhibit groups of large tubes distributed at intervals among those of average size ; but the true import of these appearances hardly admitted of recognition save by the light of Mr Moseley's researches upon the living Hcliopora. I have, however, now thoroughly satisfied myself that the corallum in Monticidipora is, in gen- 1 Until the publication of Mr Moseley's researches upon the structure of the re- cent Heliopora (Phil. Trans., vol. clxvi. p. 92, 1876), the closely tabulate interstitial tubes of Heliolites and allied forms were generally, and very naturally, regarded as being of the nature of a vesicular " coenenchyma." If, however, the inter- stitial tubes o{ Heliolites are to be regarded as formed by a special series of modi- fied polypes — as Mr Moseley's researches seem to render certain — then we cannot avoid the conclusion that the interstitial tubes of so many of the Monticuliporoids are essentially of the same nature. We m.ust therefore abandon the term of " coenenchymal tubules," as applied to the small interstitial corallites of Mon- ticiclipora and its allies Fistiilipora, M'Coy, Constellaria, Dana, &c. D 50 THE GENUS MONTICULIPORA. eral, truly dimorphic, quite as genuinely as in Heliopora or Heliolites. One set of corallites may be much reduced in number, or may undergo much modification, but I believe that the existence of two different kinds of tubes can usually be demonstrated ; and the importance of this fact, from a theo- retical point of view, can hardly be overestimated. At the same time, there are forms, otherwise quite resembling the dimorphic species, in which all the corallites of the colony are apparently similar in their internal structure, and approx- imately equal in size ; so that we are not able to assert posi- tively that the corallum in Monticulipora invariably consisted of two different sets of tubes. The nature and relative development of the two sets of cor- allites which are usually present in Monticulipora constitute important elements in the framing of any classification of the numerous forms included under this general name ; though other considerations must be taken into account as well, if such a classification is to be in any way natural. Leaving this aspect of the question aside in the meanwhile, the following are the principal variations exhibited by different forms of Monticulipora as regards the nature and arrangement of the corallites : — A. Forms with a single series of corallites, which exhibit no marked differences in internal structure. a. Without spiniform corallites, and without well-marked groups of large or small tubes. Ex., M. quadraia, Rom., M. Winteri, Nich., Af. irregularis, Ulrich, M. clavacoidca, James. b. Without spiniform corallites, but with well-marked groups of large tubes. Ex., M. pulchella, E. and H., M. nndulata, Nich., M. petasiformis, Nich. c. With spiniform corallites, but without well-marked clusters of large or small corallites. Ex., AT. discoidca, James, M. moniliformis, Nich., Af. Barrandii, Nich. B. Forms with two sets of corallites, large and small, the small tubes being much more closely tabulate, or otherwise differing in structure from the large ones. a. With no spiniform corallites, with or without clusters of large tubes. Ex., M. petropolitana, Pand., A£. Newberryi, Nich., AI. Cincin- 7iatiensis, James, M. Andrezvsii, Nich., M. {Prasopord) Grayce, Nich. and Eth. jun., AI. molcsta, Nich. GENERAL AND COMPARATIVE STRUCTURE. 51 h. Without spiniform coral lites, and having numerous interstitial tubes intercalated uniformly amongst the large ones. Ex.., M. ramosa, D'Orb. (with M. ri/gosa, E. and H., and Af. Dalii, E. and H.), M. ONea/li, James, J/, nodi/losa, Nich. c. With spiniform corallites, and with numerous interstitial tubes inter- calated among the large corallites. Ex., Af. mamnnilata, D'Orb., M. calycula, James, M. Jamesi, Nich., M. U/richii, Nich., M. frondosa, D'Orb., Af. Whiieavesii, Nich. d. With spiniform corallites, but with very few interstitial tubes (these latter sometimes almost obsolete). Ex., AI. tumida, Phill., AT. gracilis, James, AI. Dawsoni, Nich. e. Spiniform corallites few or occasionally wanting, but with well- marked clusters of small tubes. Ex., AI. subpulchella, Nich., AI. Selwynii, Nich. The above rough grouping of a number of species of Mo7i- ticulipora in accordance with the nature and disposition of the coralHtes forming the colony, will show that this feature cannot be relied upon as singly sufficient for a basis of natural classification ; since, while it certainly brings together many nearly allied types, it widely separates others which in their main structural peculiarities are unquestionably closely related. At the same time, if due weight be attached to other important structural characters, such as the condition of the walls of the corallites, and the nature of the tabulae, we may safely avail ourselves of the variations in the specialisation of the coral- lites as a guide to a sound classification of the species of this difficult genus. VI. Nattire of the TabulcE. — The next point in the construc- tion of the Monticuliporoids which needs notice is the form of the tabulce, and the arrangement of these structures in the dif- ferent corallites of the colony. So far as I have seen, tabulce are never wholly absent in any Monticuliporoid, though they are sometimes {e.g., in M. irregitlai^is, Ulrich, and M. clava- coidea, James) reduced to a minimum, and may be entirely want- ing in more or less extensive portions of the corallum. In the great majority of the Monticuliporoids, also, the tabulse are "complete," and are either horizontal or slightly curved. In no case known to me do the tabulse assume what is properly called the "incomplete" type of these structures (such as 52 THE GENUS MONTICULIPORA. occurs in forms like Faiwsites hemisphcErica, Yand. and Shum.) In some members of the genus, however, we have a quite pecuHar form of " incompleteness " of the tabulse, such as I have never observed in any example of the Favositidce. In the species alluded to (namely, M. Newbei'-ryi, Nich., M. Scl- wynii, Nich., M. frondosa, D'Orb., M. Cincinnatiensis, James, AL vwlesia, Nich., &c.), the large corallites are provided with a re- markable double tabulation, which produces appearances quite readily recognised both in vertical and tangential sections. When exam- ined in longitudinal sections (fig. 7, a), the principal tabulse of each large tube are seen to form a row of lenticular vesicles on one side of the visceral chamber, each tabula being curved in such a way as to B, Part of a tangential section of the joi^ inferioHy with the tabula uext same, similarly enlarged, showing the characteristic appearance produced by beloW it in the SerieS. On the these incomplete tabulre, when the tU l J ...u ^' r >.i corallites are transversely divided. ^ther hand, the portlOU of the VIS- ceral chamber not occupied by the lenticular vesicles just spoken of, is usually intersected by a moderate number of horizontal plates, which pass from the vesicles on one side to the opposite wall. When examined in tangential sections (fig. 7, b), these peculiar vesicular tabulae are seen to extend round about two-thirds of the circumference of the visceral chamber (or sometimes to encircle it), terminating internally, or on the face turned towards the axis of the tube, in a concave free margin. Hence, in tangential sections their cut edges are seen to form deeply curved lines enclosing an excentric tube on one side, or rarely in the centre, of each of the large corallites ; while the horizontal plates which complete the tabulation of the tubes are necessarily not exhibited at all. Fig. 7. — A, Long section of two large and two small corallites of Montiailipora Sehvynii, Nich., enlarged eighteen times, showing the peculiar incom- plete tabulffi of the large corallites ; GENERAL AND COMPARATIVE STRUCTURE. 53 Whether the tabulae assume the form just described, or are of the more normal type, it is usual to find in the dimorphic coralla that there is a marked difference in the tabulation of the large and small coral! ites respectively. It is usual, namely, to find that the tabulae of the small corallites (which are always " complete " and approximately horizontal) are conspicuously more numerous and more closely set than is the case in the large tubes. In other cases, again, even where clusters of large coral- lites constitute a noticeable feature (as in AI. pulchclla, E. and H.), there is no recognisable difference in the tabulation of any one series of corallites as compared with any other. More- over, there is evidence, in some cases (as, for example, in M. tindulata, Nich.), of a distinct periodicity in the production of the tabulae, these structures being comparatively few in number, and being mostly placed at corresponding levels in contiguous tubes, thus more or less perfectly dividing the corallum into a series of concentric layers. Lastly, in those species of the group which have the corallum conspicuously divided into an axial and a peripheral zone, it is the rule to find the tabulae very sparingly developed, or even wanting, in the central and deeper portions of the corallum, and becoming numerous as the corallites approach the surface. VII. Septa and Pseudo-septa. — Nothing of the nature of " septa," in the proper sense of this term, has ever been de- tected in any Monticuliporoid ; and we do not even meet with any structures that could be compared with the imperfect spiniform septa of so many of the Favositidce. In a few forms (such as J\L iiiiplicata, Ulrich), the tubes seem to be indented on one or more sides by blunt inward projections, which might, on cursory inspection, be regarded as of the nature of septa ; but thin sections show that in these cases the apparent septa are caused by inward protrusions of the walls of the tubes, due to the development of "spiniform corallites." In one or two other cases {e.g., III. pavonia, D'Orb.), I have occasionally detected a blunt, tooth-like projection into the interior of the 54 THE GENUS AIONTICULIPORA. visceral chamber, but this is never more than a quite occa- sional thing ; and though I cannot satisfactorily explain what these projections may be, there is no reason to regard them as septa. Lastly, Mr Ulrich has separated from Moiiticidipora certain forms for which he has constituted the new eenus Atactopora (Journ. Cincinn. Soc. Nat, Hist., 1879), upon the ground that they possess pseudo-septa. I have only examined one of these forms — viz., Monticulipora{?') Ortoiii, Nich. ; but in its case I find the apparent pseudo-septa to be mere inward protrusions of the wall, due (as in AI. implicata, Ulrich) to the development of " spiniform corallites." VII. Epithecal and Opercular Strticttircs. — The only remain- ing point in connection with the general structure of the Mon- ticuliporoids which deserves a few words of notice concerns the development of an epitheca and of opercula to the corallites. An epitheca is, as a rule, only present in those types which pos- sess a discoidal form of corallum ; and in these the concave or flat under surface is normally protected by a thicker or thinner epithecal plate, which is usually concentrically wrinkled, and is sometimes marked with fine radiating strise. In other cases, though no epitheca be present, the mouths of the corallites are liable to become closed, when maturity is reached, by a delicate calcareous membrane which constitutes an opercular growth of variable and partial development. Sometimes, when " mac- ulse," or clusters of small tubes, are present, these alone appear to become sealed up in this way. In other cases (as not uncommonly in the allied group of the FisttLlipord), the small tubes in general become covered by a thin and uniformly diffused opercular membrane, the mouths of the large tubes alone remaining open ; though I cannot say that I have ever noticed this condition of parts in any typical species of JMonti- cnlipora. Lastly, there are cases (as in M. O' Ncalli, James) where certain of the calices become ultimately closed by the development in the mouth of each of a thin calcareous lid or operculum (PI. III., fig. ^i^). This phenomenon is precisely GENERAL AND COMPARATIVE STRUCTURE. 55 similar to what occurs in certain species of Favosites {e.g., F. clausa, Rom., and F. Forbcsi, E. and H., van tuberosa, Rom.) ; and, as in these, it does not appear that the opercula are developed in any uniform manner, some parts of the surface showing these structures, while in other parts the calices are open. 56 CHAPTER III. DEVELOPMENT, AFFINITIES, AND SYSTEMATIC POSITION OF MONTICULIPORA. DEVELOPMENT. The subject of the development of the Monficiiiiporo', so far as we can be said to know anything about it, is so closely con- nected with the subject of the systematic relations of the genus, that I shall here introduce the little I have to say on this head. My own actual observations upon this point, indeed, have been principally made in connection with an examination into the views published upon this subject by Dr Gustav Lindstrom (Ann. Nat. Hist., sen 4, vol, xviii. p. 5 et seq.); and as I find myself in this matter unable to accept the conclusions of the distinguished Swedish palaeontologist, it is only just that I should quote his account of the development of Monliciilipora at length. Upon this point he remarks : — " If numerous specimens of the common M. petropolitana, Pand., be closely scrutinised, it will be seen that its semi-globose colony, so closely resembling a Favosites in its initial develop- ment, has an origin that could hardly be suspected. It begins, indeed, as a Bryozoon, as a Discoporella, as what Hall has termed Ceramopora inibricata (Pal. N.Y., vol. ii. p. 169, PI. 40 E, figs. I a-\ i). There can be no doubt that this is closely allied to the recent Discoporclla (see Fr. Smitt, Ofv, Vet. Akad, Forhand., 1866, p. 476, PI. XI. fig. 4). The basal surface of a Montictilipora^ when the epitheca is very thin, clearly shows DE VEL OPMENT. 5 7 that it is in its first origin a Ccrainopora. The smallest Ccranio- porcB which I have hitherto seen consist of a thin circular disc with elevated edges. From the smooth centre of the superior surface four or five wedge-shaped zocecia radiate outwards, each of a length of i-5th millim., their mouths being oblique, with the inferior lip somewhat protracted. On both sides of the mouth there is a short, pointed spine. In its interior such a zocecium is transversely divided by some irregular tabulse. The interstitial tubes which are so characteristic of the Discopoi^el- lidcE are also distinctly seen between the zooecia of Ceramopora. New zooecia are budded forth in quincunx from the corner of the old zooecia, and in the periphery of the colony they become more crowded, having the mouth oval and erected. In the interstices is seen what might be taken for a coenenchyma ; but this in reality is composed of nothing but smaller irregular zocecia. When the colony has spread out laterally, there are seen at the sides of the first smooth centrum several others regularly distributed on the surface, from which zooecia radiate just as if the disc were composed of an aggregation of coales- cent initial buds. When the colony has thus gained the expanse of an inch or more, the zooecia grow vertically upwards, and the colony by-and-by assumes a semi-globular shape, and is con- verted into a Montiatlipora. All the zooecia are then tubular, their mouths quite circular, and armed with a pair of very short spines, their size varying in different cases. The larger zooecia have around them either an empty space, or, as above stated, a cellular tissue resembling a coenenchyma, and consisting of smaller circular or polygonal tubes. The walls of the zooecia are solid, without any perforations, and interiorly quite smooth and destitute of projecting ridges or septa. The tabulse are very irregular in the large tubes, being oblique or deeply sunk in the wall ; in the narrower tubes they are dense and regular. The large zooecia are clustered in groups at tolerably regular intervals, each group of six or eight members. In Upper Silurian specimens they very seldom project above the surface, and do not form the stranofe monticules which are so common 58 THE GENUS MONTICULIPORA. on the surface of the Russian Lower Silurian specimens.^ I suppose that these clusters are continuations from the original and larger zooecia, which were budded out round the smooth centra when the colony was in its Ceramopora stage. In some there is seen a sort of ' reversion,' the zooecia on the surface of Montictilipora having again assumed the unmistakable char- acters of Bryozoon, becoming oblique and radiating as in a Ceramopora. Longitudinal sections, however, demonstrate that there is a direct continuation from the tubes of the Monti- culipora into those of the Ceramopora, or that the former again have changed into the latter." Havine thus described what he believes to be the mode of development in Monticulipoi^a peiropolitana, Pand., Dr Lind- strom proceeds to give an account of the development of a Silurian fossil which he terms Monticiilipora ostiolata, and which he identifies with the Trematopora ostiolata of Hall (Pal. N.Y., vol. ii, p. 152, PI. XL. fig. 5), with the Nebulipora papillata of M'Coy {M. papillata, E. and H., Brit. Foss. Cor., p. 266, PI. LXIL fig. 4), and with Thecostegites hcmisphcBrictis of Ferd. Roemer (Sil. Faun. Tennessee, p. 25, PL IL figs. 3, 3 a). This form is stated by Dr Lindstrom to commence its existence as a Discoporella, and then to pass into what may be called the '' Fistulipora stage," each cell being now "surrounded by a mass of small vertical, circular, or polygonal tubes having the appearance of a ccenenchyma," and all the tubes, both large and small, being " traversed by tabulae of the same incomplete type as those which characterise Alonticulipora!' ^ From this " Fishilipora stage " the colony is stated to pass next into what Dr Lindstrom calls the " Thecostegites stage," in which the in- 1 It is probable that Dr Lindstrom is in error in supposing that the Upper Silu- rian specimens to which he here alludes are really identical with M. petropolitana, Pand., as the latter would seem to be really an exclusively Lower Silurian species; but as I have not seen his specimens, I can only express myself on this point with much diffidence. 2 I do not understand precisely what Dr Lindstrom may mean by " incomplete" tabulce ; but the tabular of almost all the Monticuliporce that I have examined, except AT. frondosa, D'Orb., M. Selwynii, Nich., and certain allied types, are just as " complete " as they are in the typical members of the Favositidcc. DE VEL OP ME NT. 5 9 terstitial tubes become covered with " a thin smooth calcare- ous membrane," leaving the larger tubes open, and causing their mouths to assume a circular or oval shape, and to project above the general surface. Lastly, the colony is»said to change into a Mojiticztlipora by the development of regular " monti- cules," which are " arranged in quincunx, and formed at the points where seven or eight large cells are clustered." In the preceding I have endeavoured to give a faithful account of the views which Dr Lindstrom has published as to the development of the Monticidiporcc, and upon which he, in large part, bases his view that the fossils of this genus are really Polyzoa. Not having had the opportunity of per- sonally examining the specimens upon which his views are based, it would be presumption on my part were I to impugn the accuracy of the description which he has given of the phenomena which he has observed— the more so as his justly deserved reputation is a guarantee that he has not arrived at the conclusions in question without sufficient consideration. At the same time, I regret to find myself in the meanwhile unable to accept these conclusions ; and though I cannot here enter into the subject at length, I may just briefly indi- cate the principal reasons which lead me to dissent from the views of such a high authority upon this and kindred ques- tions. In the first place, then, it is clear that the study of the development of a fossil organism is attended with difficulties much more serious than those which are incidental to a similar investigation in the case of a living animal ; since in the latter it is generally possible to trace the actual transition from one stage of growth to another. This, by the nature of the case, is rarely — one might almost say never — possible in the case of a fossil. It is true that in the passage of what he has termed the " Fistulipora stage " to the " Thecostegites stage," Dr Lindstrom states that he has actually seen the same speci- men exhibiting the characters of both stages in different parts of its skeleton. Still the passage between the two stages just referred to is a comparatively small step to make, and it does 6o THE GENUS MONTICULIPORA. not affect the fact that Dr Lindstrom has not observed — so far as I am able to understand his very clear account — the actual transition between an undoubted encrusting Ceramopora and an undoubted free and discoidal specimen of Monticnlipora petro- politana, Pand. He has examined certain specimens which show characters linking the one on to the other ; but I do not understand him to assert that he has examined specimens which in one portion show the unmistakable characters of Cer- amopora, and which in another, demonstrably older portion, exhibit the features proper to Monticnlipoi^a. I cannot, how- ever, accept any specimens except such as exhibit as individ- uals the characters of the two types, as being proof that either of the types in question has been developed out of the other. In the second place, apart from this general argument, which may easily be pushed too far, there are very strong grounds for regarding Ceramopora as an independent organism quite distinct from all the forms of Monticiilipora. Thus Ceramo- pora is most abundant in Upper Silurian and Devonian strata, in which MonticnliporcE are comparatively rare fossils, while the genus is but poorly represented in Lower Silurian strata (such as the Cincinnati formation in North America), in which Monti- culiporce are excessively abundant. An additional proof of the distinctness of Ceramopora is found in the fact that it grows to a large size, preserving unchanged its normal and proper char- acters, while the general structure and form of its tubes are markedly unlike those of the corallites of the MonticitliporcE, being reclined, with oblique and often crescentic mouths, and being either devoid of tabular, or possessing but a small num- ber of these structures. (A few tabulae are present in Ceramo- pora 0/iiocnsis, Nich., and they exist in larger numbers in what is probably an undescribed species of the genus from the Wenlock Limestone of Dudley ; but I have not detected them in the more typical C. Httronensis, Nich,, and in similar thin encrusting forms.) Moreover, the colonies of Ce^-ainopora are usually (always ?) fixed, being attached parasitically by a por- tion or the whole of the lower surface to some foreign body ; DE VEL OP ME NT. 6 1 whereas the corallum in the discoid species of Monticulipora, supposed to be developed out of the former, is usually and normally/r£'«? ; but it is very difficult to explain this fact if there be any developmental relationship between the two. Thirdly, as regards matters of actual observation, I have never been able to detect anything of the nature of a " Ceramop07'a stage " in young Montiatliporce. This is a point which is most easily observed in young examples of the discoidal species of Monti- culipoj'a, such as M. petropolitana, and the various forms allied to this ; and I can only say that the most minute examples of these forms which have come under my notice differ in no respect whatever, that I can detect, except size, as regards their external and internal characters, from fully-grown speci- mens. Fourthly, if it were the case that discoidal species of Monticulipora, such as AI. petropolitana, Pand., grew out of the thin parasitic crusts to which Hall applied the name of Ceraviopora, we ought to be able to detect the primitive " Ceramoporoid " portion of the colony at the base of thin vertical sections of colonies of the former. I have, however, examined a large number of such sections, and I have been unable to detect any difference in the structure of the lowest portion of the tubes, resting directly upon the basal epitheca, as compared with that of the fully-grown portion of the coral- lites. Dr Lindstrom states that the basal surface of a Monii- aUipora, when its epitheca is very thin, " clearly shows that it is a Ccramopora;''' but I am unable to concur in this statement. If the specimen be undoubtedly one of MontiaUipora, then I have never seen anything in its epithecal surface which could be compared with the structure of Ceramopoi^a. All that can be said, in my ©pinion, on this point is, that we meet in the Palaeozoic rocks with specimens of the thin discoidal epithecse of certain fossils (the LichcnalicB of Hall), which look like the under surface of the epithecal plate of Monticulipora petro- politana, Pand., but which might be really referable to quite different forms (as many of them certainly are), and which mostly cannot, without the preparation of thin sections, be 62 THE GENUS MONTICULIPORA. definitely referred eidier to the Coelenterata or the Polyzoa. Lastly, as regards the assertion that certain MonticuliporcE pass through a " Fistulipoi'a stage," and the apparent conclu- sion therefrom that Fistulipora, M'Coy, is only a temporary condition of Monticulipoi^a, I think it may be said that the point at issue is narrowed essentially to a question of words ; for, in one sense, it may be said that the great majority of the MonticuUpoi'cB are truly Fisttdip07^ce. That is to say, I think it can be shown that the forms which M'Coy included under the name Fisttdipora,?i\\d which Hall has subsequently termed Callopora, are, theoretically, mere subgeneric forms of Monti- ctUip07'a. It is certain, namely, that the possession of a di- morphic corallum is a common feature in most of the Monti- citliporcB properly so called, and that the FistidiporcE are only peculiar in the fact that they exhibit a special development of the smaller tubes of the corallum. If this be admitted, it is clear that the passage of a given species of Monticulipora through a " FistiiUpora stage " is a matter of comparatively small importance — from a theoretical point of view. At the same time, there is at present no reason to doubt that the forms included under the names of Fistnlipora, M'Coy, and Callopora, Hall, have a real existence, in so far that the char- acters which distinguish these types are not of a merely tem- porary and transient nature, but that they exist in unquestion- ably adult examples ; so that the retention of the iiatne Fistnli- pora, as indicative of a distinct and recognisable group, is, at any rate, capable of justification, if only upon the score of practical convenience. AFFINITIES AND ZOOLOGICAL POSITION. As regards the zoological affinities of the Monticuliporoids, there has been of late years, as is well known, a strong ten- dency on the part of palaeontologists to remove them from the Coelenterata, and to place them among the Cyclostoniatous Polyzoa. The only positive and direct evidence in favour of AFFINITIES AND ZOOIOGICAI POSITION 67, this step, so far as I am aware, Is to be found in the account of the development of the MonticttliporcE as given by Lind- strom, and I have above stated the reasons which prevent me from accepting that account. Apart from this, the chief grounds for placing Monticulipora among the Polyzoa seem to be based upon its resemblance to the genus Heteropora, De Blainv., which is a familiar Secondary and Tertiary fossil type, and of which at least two living species are now known to exist (see Waters, Journ, Roy. Micr. Soc, vol. ii. p. 390, PI. XV., 1879; and Busk, Journ. Linn. Soc, vol. xiv. p. 724, PI. XV., 1879). Under these circumstances, it will be advis- able to append here a description of the external and internal characters of the genus Heteropoi'a, so as to enable some con- clusion to be formed as to the extent and validity of any affini- ties which may subsist between it and Montiailipora, D'Orb. ; and I am enabled to do this with some advantage, as I possess specimens of one of the recent species of the genus (viz., the form described by Prof. Busk under the name of H. neozelani- ca, which name seems to be really only a synonym of the pre- viously recorded H. pclliculata, Waters), and as I have submit- ted these specimens to a careful microscopical examination by means of thin sections,^ the results of which have been pub- lished elsewhere (Ann. Nat. Hist., sen 5, vol. vi. p. 329, 1880) and are here reproduced. The genus Heteropora Is thus defined by Professor Busk in his classical * Monograph on the Fossil Polyzoa of the Crag ' (1859):- *' Polyzoarlum erect, cylindrical, undivided, or branched ; surface even, furnished with openings of two kinds ; the larger representing the oi'ificcs of the cells, and the smaller the ostioles of the interstitial canals or tubes." ^ Mr Waters informs me, in a leUer, that having examined specimens which I had sent him, he is of opinion that H. neozelanica, Busk, is identical with his pre- viously described H. pelliculata. This conclusion is doubtless correct ; but as Mr Waters has not yet published his view, and as Professor Busk has therefore had no opportunity of expressing a revised opinion on this point, I continue in the mean- while to use the former name for my specimens. 64 THE GENUS MONTICULirORA. The essential character of the genus is thus the possession of a skeleton made up of tivo kinds of tubes, larger and smaller, the latter being the most numerous. The former have always been regarded as the proper zocecia ; but the relations of the interstitial tubes or '' cancelW" to the rest of the organism have not been as yet satisfactorily established, though they have been usually regarded as serving in some way to place the cavities of the polypides in direct communication.^ With regard to the internal structure of the genus, the existence of cross partitions or " tabulae " in the tubes was long ago pointed out by Jules Haime, as regards his H. conifcra and H. pustulosa (Mem. de la Soc. Geol. de France, vol. v. p. 208, 1854). Mr Busk (Crag Polyzoa, p. 122) pointed out that the cancelli enter not at all or rarely into the central axis of the branches of the skeleton, this being made up of the thin- walled and polygonal proper zooecia. The same observer also pointed out that the " ostioles," or apertures of the can- celli, are often " completely closed by a calcareous depressed lid, which in the majority of cases, however, is perforated in the middle;" and he expressed the belief that "the remains of these hymen-like lids," left behind at successive stages of growth, might probably account for the existence in the inter- stitial tubes of some species of " partial transverse, nearly equidistant septa," giving to the tubes in question a " pecu- liar moniliform aspect." Mr Busk further indicated that in one species of the genus (viz., H. clavata of the Crag) "the interstitial orifices, or many of them, exhibit a stellate ap- pearance, owing to the projection into their interior of numer- ^ As the difference between the cancelli and the proper zooecia is one of size and shape merely, and as both sets of tubes are precisely alike in their internal struc- ture, it may be regarded as tolerably certain that the former were occupied by a set of zooids essentially similar to those inhabiting the zooecia, but modified or special- ised in some way. On this view the colony would be a truly dimorphic one. As for the perforated calcareous or chitinous opercula covering the mouths of the can- celli in parts of the skeleton (as described by Waters), we may suppose that these do not exist to begin with, but that they are developed in the last stages of the life of the zooid, and that they are produced successively from below upwards as the area of active vitality is successively carried further from the fixed base of the organism (as we see to be the case in the coralla of various species oi Favosiics). AFFINITIES AND ZOOLOGICAI POSITION 65 ous minute rays — affording thus another curious, false resem- blance to a true coral." With this exception, nothing which could be compared with the "septa" ^ of the Coelenterata has, until lately (so far as I am aware), been noticed as occurring in Heteropora. The above are the most important structural features which had been brought to light by the study of the fossil species of Heteropora ; but our knowledge of the anatomy of the genus has been greatly extended by the investigation of recent species by Mr Waters and Professor Busk, as already referred to. The leading additional character which has been thus brought to light is that the walls of the zooecia and cancelli (in the outer portion of their course) are perforated by numerous canals, which open into the cavities of the tubes by well- defined circular openings, thus placing contiguous tubes in direct communication. Having now shortly passed in review some of the more important characters of Heteropora, so far as our present inquiry is concerned, I may next give a short account of the general features of H. neozelaniea, Busk, before describing in greater detail its minute internal structure. The zoarium of this species (fig. 8, a) is " erect, composed of short divergent branches springing from a short thick stem, and soon divid- ing once or twice dichotomously, and terminating in blunt rounded extremities. The diameter of the primary branches is .2 inch, and of the terminal ones about .1 to .15 inch. The surface presents orifices " (see fig. 8, b and c) " of two kinds, though scarcely distinguishable in size. The larger ones, in the older parts of growth, have a slightly raised peristome and ^ Professor Busk, in his descriptions of the species of Heteropora, frequently employs the term "septa" to indicate the transverse plates which intersect the tubes of certain forms of the genus. Mr Waters has followed Professor Busk in this, or has sometimes employed the term "dissepiments" for the same structures. It need hardly be pointed out that these terms have such a totally different signifi- cance among the Coelenterata, that their use in this connection is undesirable, and is apt to lead to confusion. The term ''septa," in fact, should be in all cases con- fined to the radiating and vertical elements of a calcareous skeleton ; and the plates so named in Heteropora axe. the analogues of the '' iabitlo'" oi the Coelen- lerates. 66 THE GENUS MONTICULIPORA. are quite circular ; the others {cancelli), disposed more or less regularly round these, generally to the number of seven or eight, are more or less angular, and the border of the opening is never raised" (Busk, loc. cit.) Mr Busk considers his H. neozclanica to be probably distinct from H. pcliiculata, Waters, on the ground (i) of certain differences in the general form of the polyzoary, and (2) of the absence in the former of any external calcareous pellicle covering the surface, though there exists, in perfectly preserved parts of the specimen described, a thin chitinous covering closing the mouths of the tubes. Mr Waters, as before remarked, is inclined to believe that the two forms are Fig. 8. — A, A fragment of the polyzoary of Heteropora neozclanica. Busk, of the natural size (original). B, A portion of the surface of the same, apparently somewhat altered by maceration in sea-water, greatly magnified (original). C, A portion of the surface of the same (copied from Busk), apparently in a more nearly natural state, greatly magnified. Both B and c show the apertures of the zocecia and cancelli. D, Portion of the surface of H. pellictdata, Waters (copied from Waters), enlarged 25 times, and showing the zocecia and cancelli. In the upper part of the figure the cancelli (and the zooecia partially) are closed by a calcareous pellicle, which is wanting on the right-hand side of the figure. Identical, in which case the name H. neozelanica will have to be abandoned. In fig. 8, b and c, I have figured the two states of the surface which my specimen of H. neozclanica AFFINITIES AND ZOOIOGICAI POSITION. 67 exhibits, one of these being a reproduction of the excellent figure given by Professor Busk {loc. cit) I have also repro- duced the figure given by Mr Waters of the surface of H. pellictUata, as it shows characters which merit a moment's attention in this connection. The left-hand portion, namely, of this figure (fig. 8, d) shows the mouths of the interstitial tubes or cancelli, as well as some of those belonging to the proper zooecia, to be closed by a thin calcareous pellicle, which is left after incineration, and which exhibits the pecu- liarity that it is perforated with numerous minute apertures opposite to the mouth of each of the interstitial tubes. The right-hand portion of the same figure shows the character of the surface, where the pellicle just alluded to has been re- moved. There can be no question that the existence of such a calcareous (or more usually chitinous), surface-pellicle, clos- ing the cell-mouths, is a feature which speaks strongly for Polyzoan affinities ; but it should not be entirely lost sight of that very similar structures occur in certain extinct types which would almost universally be referred to the corals, and which, at any rate, are very unlike the ordinary forms of Polyzoa. Thus it is well known that various species of Favosites (such as F. Forbesi, Ed. and H., var. tiiberosa, Rominger, F. turbinata, Billings, and F. clatisa, Rominger) are liable to have the mouths of the corallites closed by a calcareous pellicle, which may cover a large part of the surface of the colony. It only remains to add, with regard to the general external characters of H. neozelanica, that the mouths of the tubes, even when fully exposed by maceration in sea-water (as in fig. 8, b), do not appear to show any signs of radiating spines (" septa "), though, as will be subsequently seen, such really exist in the interior of the cells. It may also be noted, as compared with any ordinary Monticuliporoid, that though the skeleton is clearly dimorphic, in the sense that it is made up of two sets of tubes, the difference between the large tubes (zooecia) and the small ones (cancelli) is slight and sometimes 68 THE GENUS MONTICULIPORA. hardly recognisable. The cancelli, In fact, are often nearly or quite as large as the proper zooecia (see fig. 8, b and c) ; and the chief distinction between them rests upon the gen- erally more clearly angular shape of the former, and upon their mouths not being at all raised above the general surface. As regards the intei'iial striictui''e of Heteropora neozeianica, the skeleton, as of the species of Heteropora generally, Is ramose or dendroid ; and the branches resemble those of any similarly shaped coral in being composed of fasciculate tubes which are nearly vertical in the axis of the branch, but ulti- mately bend outwards to reach the surface. We can thus divide each branch Into an axial and a peripheral or cortical portion ; and not only do the tubes in these two portions of their course differ in directiojt, but they are markedly different (as we shall see) In their actual striicture. That is to say, the structure of any particular tube is exceedingly different, according as we examine it In the axial or in the cortical part of its course. Moreover, it is in the cortical portion of the skeleton alone, or almost alone, that the in- terstitial tubes are developed, the axis consisting wholly, or almost wholly, of the proper zocecia. We cannot, therefore, arrive at a proper understanding of the true structure of Heteropora (or of any similarly constructed skeleton) without making three distinct sections, — viz., one parallel to the surface and just below it, which we may call tangential, and which is the most Important of all, as giving us the cross section of the tubes in their final and most fully developed condition ; secondly, one at right angles to the branch (a transverse sec- tion) ; and thirdly, a loJigitudinal section, dividing the branch vertically through its median plane. The following are the principal points brought to light by an examination of these three sets of sections in H. jieozelanica : — (a) Tangential Sections. — As just remarked, there are no sections which yield more interesting and valuable results than those which intersect the skeleton tangentially, just below the surface upon which the tubes open. When we examine AFFINITIES AND ZOOIOGICAL POSITION 69 such a section (fig. 9, a), we observe that it is generally quite l'"'g- 9- — Tliin sections of Hctcropoya ncozelaiiica. Busk (recent). A, Part of a tangential section taken just below the actual surface, enlarged 50 times. The zooecia are cut across in their outer thickened portion ; and the canaliculi traversing their thick walls and communicating with the smaller interstitial tubes are well shown, as are the delicate radiating spines projecting into the cavities of both the sets of tubes. B, Part of a transverse section of a branch, showing the thin-walled angular condition of the zooecia in the axis of the stems, the comparative paucity of interstitial tubes, and the total or almost total absence of connecting canaliculi in this region (enlarged 50 times), c, Part of the median longitudinal section of a branch (enlarged 18 times), showing principally the outer thickened portions of the zooecia. The section shows distinct cross partitions (or "tabulae") crossing the cavities of the tubes towards the deeper parts of the branch, as also the canaliculi crossing the walls, and the po:es representing the openings of these on the backs of the tubes. D, Part of a transverse section in its outer portion, where the zooecia are laid open longitudinally (enlarged 50 times). The section shows the peculiar structure of the thickened walls and the canaliculi crossing these. A few of the delicate radiating spines are also seen, a a, The proper zooecia ; i> l>, The interstitial tubes ; c c, The walls, with the connecting canaliculi. possible to distinguish the proper zooecia from the interstitial 70 THE GENUS MONTICULIPORA. tubes by their size, but that these two sets of tubes are in no way distinguished from one another in point of structure, while their dimensions are often very nearly the same. The tubes are all rounded ; and their walls are very thick, and are com- posed of delicate calcareous laminae arranged concentrically around the cavity, and not showing any line of demarcation between each other. In this respect the walls have the struc- ture of such species oi Montictilipoi^a as M. ramosa, M. Jamesi, &c., and differ altogether from such other species as M. pul- chella. The most remarkable feature, however, in the struc- ture of the wall consists in the presence of numerous canaliculi, which pass transversely across the thickened wall (fig. 9, a) and open at both ends by wide funnel-shaped apertures into the cavities of the tubes. In this way the zooecia and interstitial tubes are placed in direct and free communication with one another throughout the entire colony. Sections of this nature also prove with absolute certainty that these canaliculi are strictly confined to the lualls of the tubes — a point upon which, as will be seen, longitudinal sections might leave us in some doubt. Another very interesting and important point brought out by tangential sections is, that both the zooecia and cancelli are provided In this part of their course with numerous delicate radiating spines, which spring from the wall (fig. 9, a) and are directed inwards for a longer or shorter distance, usually falling short of the centre. I am not aware that the presence of these radiating spinules has hitherto been recognised as occurring in the zooecia of the recent HeteroporcB, or in the extinct forms, except in H. clavata, Goldf (according to Busk), and then only at the mouths of the interstitial tubes. ^ \r\ H. ncozclaiiica they are very slender and delicate, and often break up in thin sections, so that they may appear to be wanting in a greater or less number of the tubes ; but I have never failed to 1 Mr Waters has pointed out to me that he has described delicate radiating spines as occurring in the " cancelli" oi Discoporella radiata, as well as in other species ot the same genus. (" On the Bryozoa of the Bay of Naples," Ann. Nat. Hist., ser. 5, vol. iii. p. 276. 1879). AFFINITIES AND ZOOIOGICAI POSITION. 71 recognise their existence in some part or another of tangential sections, and have no doubt that they are in this species really present throughout the whole of the peripheral part of the skeleton. Their special interest arises from their being in appearance precisely similar to the "septal spines" of so many species of Favosites (using the term " septal " in its proper signification). (b) Transverse Sections. — The appearances presented by transverse sections vary according to the part of the section which may be looked at. The central portion of such a section exhibits the tubes in the axial portion of the branch divided at rio^ht angrles. In the circumference of the section, on the other hand, the tubes are divided more or less nearly longitudinally, owing to their curvature on nearing the surface ; while this part also shows them in the thickened condition which they possess in the cortical portion of the branch. The appearances presented by the periphery of transverse sections are therefore the same as those shown in the corre- sponding region in longitudinal sections, and need not be con- sidered till we come to speak of the latter. In the central region of a transverse section (fig. 9, b) we can study the con- dition of the tubes in the axis of the branches before they bend outwards to the surface ; and we find that their structure is very different from that which they possess in the cortical region (as seen in tangential sections). Instead of being rounded and thick-walled, and provided with a largely de- veloped canal-system, they are now thin-walled, and angular or polygonal in shape, and the canaliculi of the wall seem to have totally (or almost totally) disappeared. There is also an apparent total absence of the radiating spines which are de- veloped in the cortical part of the tubes. Lastly, the tubes in this region appear to be almost entirely, or entirely, referable to the proper zooecia, the interstitial tubes or cancelli existing only, or mainly, in the cortical region. (c) Longitudinal Sections. — These show precisely the same differences, as regards their central and peripheral portions, as 72 THE GENUS MONTICULIPORA. have been already noted in transverse sections ; but it is now necessary to briefly direct attention to both parts of the sec- tion (fig. 9, c and d). In the central portion of the section (supposing the slice to be taken in the median plane) the tubes are seen in the axial portion of their course, where they are nearly vertical, and where they exhibit the features which I have pointed out as characterising them in the central region of transverse sections. That is to say, they are here provided with thin and delicate walls, in which the canal-system of the cortical region seems to be very slightly developed or want- ing. The chief point to notice about the tubes in this part of their course (and it is one that I have never failed to recog- nise) is, that their cavities are here crossed by transverse cal- careous plates or " tabulae " (the " septa " of Professor Busk and Mr Waters), which, though few in number, are "complete" and in every way well developed (fig. 9, c). On the other hand, in the peripheral portion of their course (where the appearances are precisely the same as in the corresponding region of a transverse section) the tubes have very much thickened walls, and the walls are crossed at right angles by numerous canallcull, which open at both ends into the cavities of the tubes by trumpet-shaped apertures. In all parts of the section, also, where the inner surfaces of the tubes are brought Into view, these exhibit numerous rounded apertures or pores, which represent the mouths of the said canaliculi, and which have been well described and figured by Professor Busk and Mr Waters {loc. cit.) It is very difficult in the outer part of these longitudinal sections to distinguish between the proper zooecia and the interstitial tubes or can- celli, their size being very much the same, and their internal structure being exactly alike ; and this leads me to make a few remarks upon another point. When, namely, such a section as I now speak of Is examined with the ^-inch ob- jective, it is seen that the wall separating contiguous tubes exhibits a central light space, limited on both sides by dark and definite boundaries, and crossed by the transverse canall- AFFINITIES AND ZOOLOGICAL POSITION. 73 culi which have been already described (fig, 9, d). There is . thus created an appearance of a central tube in the interior of the wall ; or rather, what I have here described as the wall might possibly be taken to be really one of the smaller inter- stitial tubes divided longitudinally. Apart, however, from the difficulty of conceiving how the canaliculi could be continued across and through the cavity of an interstitial tube, we have in tangential sections, as previously remarked, the conclusive proof that this is not the case, but that we really have to deal with the wall of the tubes. These sections, in fact (fig. 9, a), prove beyond a doubt that the canaliculi are entirely confined to the walls separating contiguous tubes, whether these be the proper zooecia or the cancelli. So far as I have seen, no " tabulae," or but an occasional one, seem to be developed in the outer thickened portion of the tubes ; but it is often possible to recognise the delicate radiating spines or " septa," which are so well displayed in tangential sections. Lastly, owing to the unequal thickening of the walls of the tubes, it is not uncommon for the longi- tudinal section of their cavities to assume a beaded appear- ance, though this is not constant, and, when present, varies much in amount. Having now fully considered the structural characters of a recent species of Heteropora, it may be as well to summarise the chief points of resemblance and difference between Hetero- pora and Monticulipora, and to state the general conclusions at which I have arrived as regards the possible relationship of these two genera to one another : — (i) As to the general form of the skeleton, the two genera are very similar, though this point is of itself wholly without significance, and the latter genus comprises types of very varied shape and mode of growth. If, however, we compare Heteropora with the ordinary dendroid types of Monticulipora, we have in both a skeleton made up of slender fasciculate tubes, which are nearly vertical in the centre of the branches, and then curve outwards, gently or abruptly, to reach the 74 THE GENUS MONTICULIPORA. surface. In both, therefore, there are estabHshed two distinct regions of the colony, an axial and a peripheral region. In both, moreover, these two regions are very different in internal structure, the tubes in the axial region of their course being thin-walled and polygonal, while in the peripheral region their walls are thickened, and they often become more or less rounded in form. In both, further, it would appear that any special interstitial tubes that may be present are developed in the peripheral region only, and extend either not at all, or to a very limited extent, into the axial part of the corallum. (2) As regards the dinwrpJiisiii of the corallum, all the most characteristic and typical species of Montiadipora consist of at least two, and sometimes of three, distinct sets of tubes, which generally differ both in size and in internal structure, and which are differently arranged in different cases. In Heteropoi'a the skeleton consists of a series of large tubes surrounded by smaller interstitial tubes ; but it does not appear that there is any special difference in the internal structiwe of these. In neither genus are we acquainted with the soft parts ; and therefore we cannot assert positively that this dimorphism has precisely the same significance in the two genera, while there are orrounds for thinking that the reverse is the case. (3) As regards the structure of the wall^ the visceral cavities of the tubes of JMonticulipora appear to be always closed, no traces of any pores or canals in the wall having yet been clearly proved to exist. In the case of Heteropora, on the other hand, the thickened walls of the tubes, in the peri- pheral part of their course, are traversed by an exceedingly well-developed series of transverse canaliculi, which open into the cavities of the tubes by definite pores, and which thus place the body-chambers of contiguous zooids in direct com- munication. These " canaliculi " differ structurally from the " mural pores " of the Favositida;; chiefly in being tubes with definite walls and dilated extremities, instead of being mere circumscribed deficiencies in the wall. (4) No radiating " septa," in the form either of spines or of AFFINITIES AND ZOOLOGICAL POSITION. 75 lamellae, are known to exist in any species of Monticulipora. In some species oi Heteropora, on the other hand, the tubes, in the peripheral part of their course, are intersected by numer- ous delicate spinules, which are arranged in a radiating man- ner, and reach a considerable distance into the body-chamber (sometimes nearly to its centre). These spinules in form and arrangement precisely resemble the " septal spines " of many species of Favositcs ; but, admitting the Polyzoan affinities of Heteropora, it is obvious that they cannot be compared homo- logically with the septa of any Coelenterate. (5) Transverse partitions, or " tabulae," are universally de- veloped in the corallites of Moutictilipora ; and it is very common for the different kinds of tubes which make up the corallum to show marked differences in the nature and degree of their tabulation. In Heteropora ncozclanica, Busk, tabulae are, so far as I have seen, always present, though their number is comparatively small. They are also undoubtedly present in other species, and in greater numbers {e.g., in //. conifera, Haime, and H. pustttlosa, Haime). So far as H. neozelanica is concerned, the tabular seem to be confined to the axial region of the corallites, and not to be developed in the interstitial tubes at all, thus difterincr in both of these respects from the tabulae of MofUiailipora. As in the case of the radiating spines, however, just noticed, if we concede the Polyzoan affinities of Heteropora, then the transverse parti- tions which cross its tubes must have a different value and import from the " tabulae " of Favositcs and of the so-called " Tabulate Corals " in Qreneral. (6) Lastly, as to the supposed relationship between Mon- ticiUipora and Heteropora, and as to the deduction which has been drawn from this as to the propriety of referring the former genus to the Polyzoa, it is clear that the points of like- ness between the two are by no means so weighty as the points of difference. On the one hand, we have a strong ex- ternal resemblance, a general similarity in the mode of con- struction of the skeleton, and an agreement in the fact that 76 THE GENUS MONTICULIPORA. in both genera the colony consists of two sets of tubes, while both have their tubes crossed by transverse partitions. Such transverse partitions of the tubes (or, as we may loosely call them, " tabulce ") occur, however, in organisms of such exceedingly diverse affinities, that we can, admittedly, attach no value to the last mentioned of the above resemblances. A mere similarity in general form, appearance, or mode of skeletal conformation is also of no classificatory weight, since we could find species of Favositcs or Pac/iypora which in these respects are quite like either Moiiticulipoj-a or Hctero- pora ; so that, after all, the resemblances between the two genera under consideration dwindle down to a comparatively small quantity. On the other hand, to set against the mostly superficial points of resemblance above noted, we have a number of fundamental structural differences. Thus, in jMontiaUipoi-a the walls of the tubes are imperforate, there are no traces of radiating spines or " septa," and in the dimorphic or trimorphic species there are usually important structural dif- ferences as regards the different groups of corallites. In Hetei'opora, on the contrary, the walls of the tubes are tra- versed by a very remarkable and exceptionally developed canal-system, the tubes possess in their outer portions a well-developed series of radiating spines arranged in vertical rows (sometimes, at any rate, if not always ^), and the inter- stitial tubes are in no way structurally different from the proper zooecia. In the face of the above distinctions, I feel compelled to believe, in the meanwhile, that there is no real relationship at all between Heteropora and Montictdipora. This belief would not, of course, constitute any valid ground for denying 1 It is true that radiating spines have not generally been observed in Heteropora, and that even in H. neozelanica, where they are plentifully developed, they seem not to have been noticed by such excellent observers as Professor Busk and Mr Waters. I ascribe this, however, to their very fragile nature, and to the general neglect of tangential sections, in which alone they can be readily made out ; and I entertain little doubt that they occur generally in the genus. AFFINITIES AND ZOOLOGICAI POSITION 77 the possibility that Monticiilipora may truly belong to the Polyzoa rather than to the Coelenterata ; and on this point I prefer at present to come to no absolutely final conclusion, though my opinions lean decidedly towards the latter as a proper resting-place for the genus. It must, however, be evident, that in supporting (as many palaeontologists now do) the Polyzoan affinities of Mojiiiculipora, little or no weight can in future be attached to the likeness which the genus shows to Heteropo7^a. It may be also pointed out that, in our present ignorance of the miiinal of Heteropora, it is per- haps not entirely without hazard that we should unhesitat- ingly assign it to a place among the Polyzoa. I do not at all overlook its resemblance to many undoubted Cyclostom- atous Polyzoa, nor am I in any way prepared to deny its Polyzoan affinities ; but I cannot entirely ignore the fact that the pore-canals, septal spines, and tabulae, which are now known to exist in some species of the genus Heteropora, are, at any rate, as reconcilable with its reference to the Coelenterata as to the Polyzoa. (7) Leaving Heteropora out of sight, there are no other forms of the Polyzoa to which Monticulipora makes such a near approach as to render any very close comparison neces- sary. In any case, also, it is clear that very little weight indeed can be attached to mere external resemblances in form and general aspect in a matter of this kind. Thus we find the common Favosites Canadensis^ Billings, sp., of the Devonian of Canada, to be so entirely similar in the form and appearance of its colonies to examples of Fistitlipora, M'Coy, that it was unhesitatingly referred to this genus (which Dr Lindstrom re- gards as clearly Polyzoan) by Mr Billings and myself. Dr Rominger, however, showed that it has "mural pores" of the regular Favositoid type — a discovery which I have myself verified — so that in place of being a Fistulipora, and there- fore, according to Dr Lindstrom, a Polyzoon, it is a true Per- forate Coral. A position among the Favositidce has similarly been now established as the right one for Stenopora, Lonsd., 78 THE GENUS MONTICULTPORA. which Includes forms so Hke Chcptetcs and Monticiilipora in general aspect as to have been commonly included under one or other of the latter heads. Apart from mere superficial appearances — which in this case speak at least as strongly for a Coelenterate as a Polyzoan alliance — there is nothing in the actual structure of Monticiilipora which would not entirely agree with its being a coral. The only point which could be mentioned which would in any fundamental manner distinguish the internal structure of a Monticiilipora from that of, say, Tetradiuni or Heliolitcs, is the absence in the former of septa. I do not, however, attach any weight to this, partly because some undoubted corals are equally without septa, partly because the septa in Hcliolites and its allies are now known by the researches of Moseley to be only " pseudo-septa," and partly because I do not think that any important change in classifica- tion should be based upon a merely negative character. On the other hand, there are strong resemblances between Mon- ticiilipora and its allies and various undoubted corals — prin- cipally, perhaps, the Hclioporidcr. Thus the " tabulae " of the Monticuliporoids are in all respects similar to those of such undoubted corals as Favositcs among the Zoantkaria, and Heliolites among the Alcyonaria. Again, there is the import- ant character that the corallum of the Monticuliporoids can be shown to be so very commonly dimorphic, consisting of two distinct sets of corallites, of different sizes, and mostly with a different internal structure. This last character reminds us so strongly of the Helioporidce — to which there are other men- tionable points of likeness — that I am at present disposed to regard the Monticuliporidce as an ancient group of the Alcy- onaria, at the same time, of course, that I regard the group as a quite independent one, and as quite distinct from the former family. 79 CHAPTER IV. RELATIONS OF MONTICULIPORA TO CH^TETES, STENOPORA, TETRADIUM, CERAMOPORA, AND HETERODICTYA. We have now considered the structure of Hderopora, Blainv., which, of all other types, is perhaps the one which presents the closest general resemblance to certain forms of the Monti- culiporoids. There are, however, various extinct organisms which are so 'like Monticnlipora, either in appearance or in actual conformation, or in both of these points, that it be- comes necessary to examine how far this likeness is merely superficial, and how far it may be based upon real affinity. Amongst the forms which require consideration in this con- nection, the first place must be given to those which are com- prised in the genus Chcetctes, Fischer (Oryct. de Gouv. de Moscou, p. 159, 1837). These forms, in fact, are so similar in most respects to the massive types of MonticiUipora (such as M. undniata, Nich.), that it is only of late years that it has been found possible to indicate definitely the grounds upon which the latter genus might be separated with anything like scientific precision from the former. The corallum in Chcstetes, Fischer, is massive, composed of long irregularly prismatic erect corallites, which are closely contiguous, and are com- pletely amalgamated by means of their walls. The corallites are all of one kind, both as regards size and internal struc- ture, and open upon the surface by irregularly polygonal non- oblique calices. There are no true septa, but the visceral chambers are often partially divided by an imperfect longitu- 8o THE GENUS MONTICULIPORA. dinal partition (or by two such partitions), resulting from the uncompleted fission of the tubes into two young corallites. Complete and remote tabulae are also present. It will be seen from the above description how close is the general likeness between ChcEtetes, Fischer, and the massive forms of Monti- ailipora, D'Orb. ; and there are only two characters by which the two groups may be satisfactorily differentiated. The most important of these characters concerns the structure of the walls of the corallites. Thus, in ChcBtetes it will be seen by thin sections (fig. lo) that the walls of contiguous corallites Fig. lo. — A, Tangential section of Clnrtc'tcs radians, Fisclier (var.), from tlie Carboniferous Limestone of Shap, Westmorland, enlarged i8 times; B, Vertical section of the same, similarly enlarged. are invariably entirely and undistinguishably amalgamated or fused with one another, all traces of the originally duplex character of the partitions between neighbouring tubes being now lost. It is true that there are species oi Monticnlipora (as, for example, M. tnviida, Phill.) in which the walls of con- tiguous tubes, as seen in tangential sections, are apparently fused with one another ; but in such cases, we have seen that the fusion is only apparent, since rough fractures always expose the exterior of the tubes. In ChcBtetes, Fischer, on the other hand, the amalgamation of the walls of the corallites is shown to be real by the fact, long since pointed out by Lons- dale (Geol. of Russ., vol i. p. 595, 1845), that rough fractures expose the interior of the tubes. Mr Lonsdale at the same time pointed out that the corallum in Chcrictcs increases fissi- RELATIONS TO EXTINCT ORGANISMS. 8i parously, and that we might to this fact ascribe the second pecuharity of the genus — namely, the existence in many of the coralhtes of imperfect vertical partitions (generally one or two in number in any particular tube). These partitions appear in tangential sections of the corallum as blunt tooth-like pro- cesses projecting into the interior of the corallites (fig. lo, a), and they might be taken at first sight as being " septa." They are, however, wanting in many of the tubes ; and there is little doubt that they are really due to the fact that the corallites which possess them have begun to divide by fission. While the points above noted enable us to separate the species of Chcstetes, Fischer, from those of Montintlipora, it is not so easy to definitely separate the latter from Stcno- pora, Lonsd. The typical species of Stcnopora, Lonsd. {iion M'Coy) possess a ramose or sublobate corallum, composed of tubular corallites, which are nearly vertical in the centre of the branches, and radiate outwards from an imaginary axis to open on all points of the free surface. In the centre of the branches the corallites (like those of the dendroid species of Montictdipord) are thin-walled and polygonal, but they be- come thickened as they approach the surface, and they are never amalgamated with one another by their walls. The thickening 1 m m Fig. II. — A, Poi-tiou of a branch of S/LiioJ^ora Jackii, Nich. and Etli. jun., split open, of the natural size ; B, Portion of tlie same enharged, showing the annulations of the tubes in their outer portions ; c, A few of the tubes of the same still further enlarged, showing the mural pores. Permo-Carboniferous formation, (Queensland. of the walls of the tubes in the latter portion of their course takes place in the same way as in many JMontic^iliporcc {e.g., M. tiunida, Phill.) — namely, by the deposition of superimposed lamelLne of sclerenchyma round the growing margins of the 82 THE GENUS MONTICULIPORA. corallites ; but these lamellae are produced intermittently instead of uniformly, and a marked difference in structure is thus caused. In those MonticuUporce, namely, which possess thickened walls, rough fractures show that the walls of the tubes are approximately smooth and even, while longitudinal sections show that the thickening is uniformly augmented, or remains nearly the same, from the point where the tubes begin to bend outwards to their apertures (see PI. III., figs, i e, I _/). On the other hand^ rough fractures of specimens of Stenopora, Lonsd., show that the thickening of the tubes is periodically effected, so that the outer surfaces of the tubes exhibit a number of annulations or ring-like accretions, separ- ated by intervening flat spaces (fig. ii, b and c). Some species show this feature more conspicuously than others, but almost all (all the typical species) show the same fact in ^A/- Fig. 12. — Minute i.ixwz'iwx'i q{ Stcnopora Ho7i'sii,Kvc\\. (spec, nov.), from the Carboniferous rocks of Redesdale, Northumberland. A, Part of a tangential section, enlarged eighteen times. B, Another part of the same section, similarly enlarged, showing the thick-walled corallites, with the numerous hollow spines in the wall. Some of the tubes also show the pecuHar perforated tabulce. c, Part of the exterior of a transverse section, where the tubes are cut longitudinally, enlarged eighteen times. This section shows the peculiarly thickened moniliform wall which is characteristic of Sieitopora, some of the tabula; being complete, while otliers show a central deficiency. (From the collection of Richard Howse, Esq.) an even more striking and instructive manner when examined by means of thin longitudinal sections (fig. 6, a, and fig. 12, RELATIONS TO EXTINCT ORGANISMS. 83 c). In such sections the walls appear to be conspicuously moniliform, belnor composed of fusiform thickened regions, which alternate with comparatively delicate unthickened tracts of the wall. This peculiar structure of the w^all is more or less strikingly characteristic of all the species of Stenopora, Lonsd., with which I am acquainted ; and it constitutes the most marked structural feature, perhaps, by which we may readily separate this genus from JMonticiilipora. There are, how- ever, other characters by which, when they can be detected, Stenopora, Lonsd., can be distinguished from any of the Alonti- culiporoids. The most important of these characters is the presence in Stcnopora of " mural pores," precisely similar in their nature to the openings in the walls which go by this name in Favosites. Some species of Stenopora (as S. yackii, Nich. and Eth. jun., fig. 11, c) show these pores in an un- mistakable form ; but they are always minute in point of size, and remote and Irregularly distributed, and there are various species of the genus In which they have not yet been detected. In spite, therefore, of the fact that these apertures must always be present in the genus, It must be admitted that the difficulty which attends their recognition is so great that they are prac- tically of little use In enabling us to distinguish the species of Stenopora from those of Monticulipora. Another feature which is characteristic of Stcnopora Is, that many of the calices may be closed by a concave diaphragm, perforated with a central oval or circular aperture. This feature is well seen In examples of the form which I have named Stcnopora Howsii} and of which I have figured the 1 Stcnopora Howsii, Nich. — As this species— the only undoubted form o[ Stcno- pora, Lonsd., from British rocks with which I am acquainted — has not been pre- viously described, I append here a brief diagnosis of its characters. Corallum ramose, of large size, fragments being over six inches in length, with a diameter of seven lines. Stems sub-cylindrical, with slight tumid enlargements at intervals, the branches remote, and given off alternately from opposite sides of the main stem. Large calices moderately thin-walled, polygonal, about i-6oth inch in diameter, with a larger or smaller number of intercalated minute tubules, the latter sometimes forming " maculae" or irregular aggregations. Calices sometimes open ; sometimes closed by a concave diaphragm, perforated centrally by an oval or circular aperture. Walls of the tubes periodically thickened, and annulated externally in the outer 84 THE GENUS MONTICULIPORA. internal structure above (fig. 12). It was also noticed by Mr Lonsdale, in his descriptions of the species upon which he originally founded the genus (Darwin's ' Geological Observations on the Volcanic Islands,' Appendix, 1844). Somewhat similar phenomena are, however, observable in some AIontiadipoi'cE I and the character in question, so far as I have observed, is never more than a partial one in any species of Stenopora. That is to say, most of the calices in Stenopora will be found to be open, and it is only in some of them — generally in patches — that these peculiar perforated diaphragms can be detected. As a test of the relations of any given specimen, this character, therefore, can- not be relied upon. Another and a very striking feature, arising out of the preceding peculiarity, may be occasionally observed in longitudinal sections of the corallites of Stenopora ; and that is, that certain of the tabular are perforated by a central aper- ture, thus showing themselves in section as two opposing ledges running out from opposite walls of the corallites, but not meeting in the centre. This remarkable imperfection of the tabulae is one of the most striking characters of Stenopora Howsii, Nich. ; but even this form possesses some tabulae which seem to want this perforation (fig. 12, b), and I have not observed the same thing in any other species of Stenopora. Upon the whole, therefore, the most readily determinable peculiarity, and the one which appears to be most universally present, is the periodic thickening of the walls of the coral- lites in their outer portions in Stenopora, as compared with the uniform thickening, or the absence of thickening, which is characteristic of the corallites of Monti cttiipoj'a. The more massive species of Alonticiilipora, such as ]\I. portion of their course. Tabula; sometimes complete, sometimes with a central perforation. No septa. Mural pores not observed. The only specimens of this remarkable species that I have seen were collected by Mr Howse in the Carboniferous shales of Redesdale, Northumberland, and it is to his kindness that I am indebted for the opportunity of examining them. I shall describe them at greater length on another occasion ; but in the meanwhile the above brief diagnosis will serve to characterise the species. RELATIONS TO EXTINCT ORGANISMS. 85 {Monotrypd) nndulata, NIch., present a general resemblance to the forms which constitute the orenus Tetradmni, Dana. In both, the general aspect of the coralhim is at first sight very similar, but there are fundamental differences in their internal structure. Thus, in Tctradmiu the walls of adjoining coral- lites are only doubtfully separate (probably they are really amalgamated, as in ChcEtctcs, Fischer) ; while the corallites, as seen in section, have a peculiarly cruciform or petaloid form (fig. 13, b), due to the presence in each of three, or more com- F'g- '3- — A, Fragment of a large corallum of Tetraduim niiiuis, Safford, from the Cincinnati Group of North America, of the natural size ; B, Transverse section of the same, enlarged ten times, showing the petaloid form of the tubes and the short septa; C, Vertical section of tlie same similarly enlarged, showing the tahulie. monly four, delicate lamellar septa, which look as if they were formed by inward foldings of the wall, and which extend for a short distance only towards the centre of the visceral cham- ber. The tabulae are usually complete and horizontal (fig. 13, c) ; and even when to some extent incomplete, they never show the peculiar structure which is characteristic of such forms of Moiiticulipora as those constituting the sections Pj'asopora and Pej'onopora. Moreover, the corallites of Tet radium are all of one kind, and there are none of the closely tabulate interstitial tubuli which form such a conspicuous feature in most Monti- culiporoids. From all the Helioporidcs, the Monticuliporolds are funda- mentally separated by the total want of pseudo-septa in the large corallites of the colony. In other structural features, 86 THE GENUS MONTICULIPORA. many Monticuliporoids, especially those which are referable to Fistulipora, M'Coy, present a close general likeness to Helio- lites; and It was not without considerable apparent reason that Milne-Edwards and Halme regarded the FistuUporcs as refer- able to the same group as Heliolites. The absence of pseudo- septa affords, however, sufficient ground for the separation of all the Monticuliporoids from the Helioporidce, at the same time that the general likeness between the two groups is strono'lv susfSfestlve of the existence of a real zooloo-Ical relationship. It only remains to briefly compare the Monticuliporoids with the singular Palaeozoic Polyzoan genera Ceraniopora, Hall, and Hcterodictya, NIch. So far as the first of these Is concerned, there is no difficulty in' separating even the en- crusting species of Monticulipora as distinct, if we take those forms of Ceramopora which, like C. inibricata, Hall, and C. Hiironcusis, NIch., form very delicate parasitic expansions on foreign bodies. In such cases, the colonies of Ceramop07'-a are readily distinguished by the peculiar crescentic form of the mouths of the tubes ; while I am not aware that they have been shown to possess tabuke. On the other hand, there are forms apparently referable to Ceramopora (such as C. Ohio- ensis, NIch., and an abundant but undescrlbed species in the Wenlock Limestone of Dudley), which, though primitively, and generally permanently, encrusting, are nevertheless some- times found to attain a considerable thickness, either by the simple upward growth of the tubes, or by the superposition of successive layers. Such forms may make a close approach to certain of the Monticuliporoids in general aspect, and may come to resemble the latter closely in their internal structure. I hope to find a future opportunity of discussing the structure of these peculiar types at greater length. In the meanwhile, therefore, I merely figure their minute Internal structure (fig. 14), and make a few brief and general remarks. As above noted, the general aspect of such forms Is not at all unlike that of certain Monticuliporcr ; but even so far as this Is con- RELATIONS TO EXTINCT ORGANISMS. 87 cerned, there are some peculiarities in the general fades of the former which would at once lead the observer to separate Fig. 14. — Minute structure of Ccrantopora. A, Tangential section of Ccramopora O/iiociisis, Nich., from the Cincinnati Group of Oliio, enlarged eighteen times; B, Part of a longi- tudinal section of the same, similarly enlarged, showing the presence of tabulae ; C, Part of a transverse section of the same, similarly enlarged, showing the thickened cell-walls ; n. Part of a tangential section of an undescribed species of Ceramopora, from the Wen- lock Limestone of Dudley, enlarged eighteen times; E, Vertical section of the same, similarly enlarged, showing the well-developed tabula. them as distinct. Thus, the tubes of which the colony are composed always open upon the surface in an oblique manner, reminding one of Alveolites rather than of Monticiilipora, and the calices are invariably either very irregular in shape, or are, more usually, distinctly crescentic or lunate, one lip of the aperture being strongly curved. As regards internal structure, the general conformation of the skeleton is quite like that of some of the IleterotrypcE amongst the Monticuliporoids, the tubes being comparatively thin-walled in the vicinity of their points of origin, but becoming thickened by a secondary deposit of laminated calcareous matter as they approach the surface. There are, also, small tubules intercalated amonof the proper tubes of the colony ; and lastly, there exists a 88 THE GENUS MONTICULIPORA. larger or smaller number of well-developed complete tabular (fig. 14, B and e). On the other hand, the interstitial tubes are not provided with any tabulce, instead of being closely tabulate, as they would be in any species of Hetcrotrypa or FisttUipora among the Monticuliporoids ; and they appear, indeed, to be quite superficial, and not to extend inwards to such an extent as to render them a conspicuous feature in sections which cut the tubes longitudinally. Moreover, there are grounds for believing that distinct apertures are present in the walls of the species of Ccramopora in question, though I do not feel sure that this is the case. The above differences in structure, however, combined with the different external aspect, are sufficient to enable us to effect in general a satis- factory separation between the species of Montictdipora and any of the known forms of Ccramopora, Hall. With regard to the Polyzoan genus Heterodictya, Nich., the only necessity for entering into any comparison of its structure with that of Alonticidipora arises out of the fact that such an excellent observer as Mr E. O. Ulrich has referred (Cat. Foss. Cincinnati Group, 1880) the form which I believe to be Alonticiilipora pavonia, D'Orb., to the former. I am, however, quite unable to accept this conclusion, though I do not feel disposed to assert positively that M. pavonia, D'Orb., with its various abnormal characters, is an indisputable Mon- ticuliporoid. In Heterodictya, Nich., we have to deal with an undoubted Polyzoon, of the general type of Ptilodictya. The colony forms a thin falciform expansion which is composed of two layers of tubes diverging in opposite directions from a definite striated median calcareous lamella, and which is bounded by perfectly definite margins, and has a perfectly definite shape. As regards internal structure, the only re- semblance between Heterodictya and any of the Monticuli- poroids is to be found in the existence in the former of well- developed tabulae (fig. 15, a and b), which, however, are often incomplete. No interstitial tubes are present, nor are there any "monticules" or structures comparable with these. RELATIONS TO EXTINCT ORGANISMS. 89 I do not myself know of any Monticuliporoid which could be compared with Heterodictya except M. pavonia, D'Orb. : and Fig. 15. — Minute structure o^ Hdcrodictya gigantea, Nich. , from the Corniferous Lime- stone (Devonian) of Canada. A, Vertical and longitudinal section, showing the well- developed tabulre ; B, Vertical and transverse section, showing the incomplete condition of many of the tabulre ; c, Tangential section. All tlie figures are enlarged eighteen times. this is, in my opinion, sufficiently separated from the former by its want of any definite form, or of definite and structurally differentiated margins ; by the absence of a complete median calcareous lamina, which is so clearly a distinct structure that the layers of tubes can be readily stripped away from it ; and by the possession of distinct '* monticules." The tabulae of M. pavonia, D'Orb., are even more feebly developed than in Heterodictya ; but this is a feature of no importance — whereas the striking difference in general aspect, in the want of obli- quity to the calices, in the permanent distinctness of the walls of adjoining tubes, and in the structural characters above noted, sufficiently prove that M. pavonia cannot, at any rate, be referred to the genus Heterodictya. 90 CHAPTER V. THE SUBDIVISIONS OF MONTICULIPORA. From a theoretical and strictly scientific point of view, the family of the Montic2tliporidcu must be regarded as comprising only the single genus MontiaLtipora, D'Orb. That is to say, our present knowledge does not appear to be sufficient for the establishment of any subdivisions within the limits of this com- prehensive genus, which are so markedly distinguished by their structural characters that they would take rank as natural and undoubted genera. Hence I have formerly divided the genus ]\Ionticulipora into the six sub-generic groups, Fistiili- pora, M'Coy, Constellaria, Dana, Dekayia, Edw. and H., Diplo- trypa, Nich., Heterotrypa, Nich., and Monotrypa, Nich. (Pal. Tab. Cor., p. 291). While the above-mentioned six groups are so closely allied to one another that there is no difficulty in framing a generic diagnosis which will embrace them all, the first three of these — viz., Fistulipora,WQ.oy, Constellaria, Dana, and Dekayia, Edw. and H. — possess certain marked structural features by which they can be readily separated from one another, often by a merely superficial examination. Upon the whole, therefore, it may perhaps be the best plan, as a matter of practical convenience, to regard these three groups as so many distinct ^^7/cr^, in spite of the fact that they have no theoretic claim to such a rank. The adoption of this method of procedure will leave JMonticnIipora proper as an independent genus, with the three subordinate groups, Diplotrypa, Hetero- trypa, and Monotrvpa, to wliich must be added as a fourth sub- THE SUBDIVISIONS OF MONTICUIIPORA. 91 genus the Prasopora of Mr R. Etheridge, jun., and myself, while I shall institute a fifth sub-genus under the name of Perofiopora. As the present work is concerned wholly with the genus Monticiilipora proper, I shall here subjoin all remarks which I find it necessary to make upon Fistulipora, Constel- lari'a, and Dekayia, at the same time briefly defining JMonticit- lipora and Its minor subdivisions. It being understood, then, as above stated, that the term gams is here used in a purely artificial sense, I propose to divide the family MonticuliporidcB into the following four genera : (I.) Fistulipora, M'Coy, 1849. (Ann. and Mag. Nat. Hist., ser. 2, vol. iii. p. 130.) Callopora, Hall, Pal. N.Y., vol. ii. p. 144, 1852. The corals of this group were separated by M'Coy to form his genus Fishdipora, with the following generic diagnosis : — " Corallum encrusting, composed of long, simple, cylindrical, thick-walled tubes, the mouths of which open as simple, equal, circular cells on the surface, and having transverse funnel- shaped diaphragms at variable distances ; interval between the tubes occupied by a cellular network of small vesicular plates." The type of the genus is the F. minor, M'Coy, of the Carboniferous Limestone of Derbyshire. At a later period. Professor Hall proposed the name of Callopora for certain Upper Silurian corals, with the following eeneric cliao-nosis : — " Ramose or encrusting species of corals, having a columnar structure ; cells tubular, with the apertures circular or petalold, not contiguous, and having the intermediate spaces occupied by angular cell-like openings which are transversely septate ; tubular cells rarely septate." ^ ' The term " septate," used by Professor Hall in the above diagnosis, is employed in the same sense as " iabulatcl' and does not refer to the presence of true septa. 92 THE GENUS MONTICULIPORA. The identity of Fistiilipora, M'Coy, and Callopora, Hall, has long been more than suspected, the chief difficulty in the way of uniting the two being that M'Coy states that the tabular in the large corallites of Fistuiipora are infundibuliform, while Hall describes radiating septa (/, ) Walls of the corallites preserving their duplex character throughout. {Ex., M. Jainesi, Nich., AI. implicata, Ulrich, M. Girvaucnsis, Nich., M. Trentonensis, Nich., AI. Dawsoni, Nich., &c.) II. DiPLOTRYPA, Nich. — Corallites of two kinds, with thin, structureless, apparently amalgamated walls ; the larger ones conspicuously polygonal, with comparatively few and remote tabulae. The large corallites may be aggregated at special points into conspicuous clusters (" monticules"), but they are at the same time scattered indiscriminately through the entire colony, and except where forming the groups just alluded to, they are partially separated by the intervention of the smaller corallites, which are always angular in shape, have 1 There are two other groups — viz., Trematopora, Hall (Dybowski), and Ditto- pom, Dyb., which appear to represent additional sub-generic divisions oi Monticuli- pora. I have not included these in the following synopsis, as I have no direct knowledge of their characters. I shall, however, give a brief account of the pecu- liarities ascribed to them by Dybowski in an appendix at the end of this work. It is also probable that some of the as yet undescribed forms which have been yielded by the prolific Silurian strata of Ohio to the researches of Messrs Nickles, Ulrich, &c., will be so far different from any of the above as to require the formation of new sections for their reception. Lastly, among the species here described there are several which are so far abnormal that it is quite possible that they will ultimately find a resting-place in some other section of the genus to that in which I have temporarily placed them. I02 THE GENUS MONTICULIPORA. thin walls, are never so far developed as to completely isolate all the larger tubes, and are always provided with more numerous and more closely-set tabulae than is the case in the latter. Spiniform corallites present or absent. Type of the group, Monticii/ipora pdropolifana, Pand. {a) Corallites prismatic. {Ex., M. petropolitana, Pand., M. JVhiteavesii, Nich.) {b) The large corallites oval or rounded. {Ex., M. calyciila, James.) III. MoNOTRYPA, Nich. — Corallites of one kind only, so far as their inter- nal structure is concerned; though there may be well-marked clusters (or " monticules ") of tubes appreciably larger than the average. Corallites usually conspicuously prismatic, their walls thin and apparently structureless, or retaining their primitively duplex character. Spiniform corallites mostly wanting (pres- ent in AL discoidea, James). Tabula complete, uniformly distributed through- out all the corallites, without respect to the size of these ; sometimes nearly obsolete. Type, Montiadipora ujidulata, Nich. {a) With thin, apparently structureless walls. {Ex., M. undulata, Nich., M. Wiiiteri, Nich., M. irregularis, Ulrich, M. davacoidea, James, I^. qiiadrata, Rom., M. calceola, Miller and Dyer, &c.) {b) Walls appreciably thickened, but preserving their duplex character. {Ex., M. petasiformis, Nich., M. pukhelia, E. and H., Pil. discoidea., James, M. pavonia, D'Orb., M. briarea, Nich., <^'c.) IV. Prasopora, Nich. and Eih. jun. — Corallites of two kinds, the smaller ones interspersed throughout the colony, or partially aggregated into clusters. Large tubes with peculiarly incomplete tabulae, which form a series of marginal vesicles, enclosing a lateral or central space, which is usually crossed by a few straight tabulae. Small tubes angular, with numerous complete and close-set tabulae. Spiniform corallites wanting, or very sparingly developed. Walls of the corallites thin and apparently structureless. Corallum usually discoid. Type, Prasopora Graycz, Nich. and Eth. jun. Other examples are M, {Praso- pora) Neivberryi, Nich., and M. {P.) St'hvyiu'i, Nich. V. Peronopora, Nich.- — Corallites of two kinds, the larger ones with tab- nice of the same peculiarly incomplete type as in Prasopora. Small tubes with close-set complete tabular. Walls of the corallites thickened, and apparently more or less completely amalgamated, so that their primitive duplex character is lost. Spiniform corallites usually largely developed (apparently wanting in M. vwlesta, Nich.) Corallum laminar or encrusting. Type of the group, J/". frondosa, D'Orb. ( = J/, decipiens, Rom.) Other examples are M. molesta, Nich., M. Cincinnaticiisis, James, and probably M. Ortoni, Nich. I05 CHAPTER VI. S/ib-ocjius Heterotrypa, Nich., 1879. (Pal. Tab. Cor., p. 293). This section includes many of the most typical and most familiar of the species of JMonticidipora, comprising- among them the M. mamniulata, D'Orb., which, as the species first on the list of Montindipora; given by D'Orbigny (Prodr. de Pal- eont., p. 25), has the right to be considered as the type of the whole orenus. In addition to M. viamimclata, D'Orb., we must place here 31. raiuosa, E, and H., M. Andrezvsii, Nich., M. Ulrichii, Nich., M. siibpulchella, Nich., M. G Ncalli, James, M. Jamesi, Nich., J\L moniliformis, Nich., ]\I. tumida, Phill., M. gracilis, James, and various other more or less certainly established species. In all these forms the corallum is con- spicuously dimorphic, and consists of two sets of corallites of different sizes. The larger tubes are sub-polygonal or some- times rounded in shape, and are more or less conspicuously thickened towards their mouths, while they usually possess few and remote tabulae, or may be in great part devoid of these structures. They are usually to some extent contiguous ; but they are always partially separated by the corallites of the smaller series, which are also sub-polygonal, sub-angular, or rounded, and more or less thickened towards their mouths. In all the corallites the tabulae are complete, and the small tubes are more closely tabulate than the large ones. Spiniform corallites are often very well developed, but at other times are I04 THE GENUS MONTICULIPORA. few or wanting. The structure of the zuall, as in ahiiost all the groups of Monticulipora, varies in different forms of the group, according to the extent to which the originally duplex character of the wall is preserved. In all, the tubes become thickened and lamellated as the surface is approached ; but in some (such as M. ttnnida, Phill., M. gracilis, James, &c.) they become to all appearance so completely united with one another in this part of their course, that thin tangential sec- tions fail to show any traces of the original lines of demarca- tion between adjoining tubes. In other cases (as in M. ramosa, D'Orb., and its varieties), these lines of demarcation can be to some extent recognised, though the apparent fusion has largely obliterated them. Lastly, there are forms (such as M. Trentonensis, Nich.) in which the primitive boundaries between the tubes are quite well preserved, in spite of the thickening of the walls. The section Heterotrypa includes many of the most typi- cal species of Montiadipora proper, and it is also the section most nearly allied to Fistiilipora, M'Coy. Its characters will be more fully understood from the following descri^^tions of illustrative species. Monticulipora (Heterotrypa) mammulata, D'Orb. (PL VI. figs, i-ig.) Monticulipora iiiammulata, D'Orbigny, Prodr. de Paleont, vol. i. p. 25, 1850. Chcetetes juai/iinitlafi/s, Edwards and Haime, Pol. Foss. des Terr. Pal., p. 267, PI. XIX. fig. I, 1851. Monticulipora nianimulata, Edwards and Haime, Brit. Foss. Cor., p. 265, 1854. CJuntetes mammidatus, Nicholson, Quart. Journ. Geol. Soc, vol. xxx. p. 508, PI. XXX. figs. 3-3(3!, 1874. Pal. Ohio, vol. ii. p. 207, 1875. MoJiticnlipora i^Hcterotrypa) inajiiiuiilata, Nicholson, Pal. Tab. Cor., p. 294, PI. XIII. figs, i-i/', 1879. Spec. Char. — Corallum in the form of thin undulateci expan- sions, from two to four lines in thickness, and often several SUB GENUS HETEROTRYPA. 105 inches in height, consisting of two layers of corallites, which diverge from an imaginary central plane to open on both sides of the frond. (Occasionally assuming a massive form ?) Sur- face covered with rounded, conical, or elongated elevations or " monticules," which are sometimes but slightly raised above the general surface, whilst in other examples they are conspic- uously elevated. These monticules are composed of corallites which sometimes appear to be slightly larger than the average, and which at other times are decidedly smaller than the ordi- nary tubes ; while in some specimens the sides of the monticules are covered by full-sized tubes, and the summit is occupied by smaller corallites. The distance between the monticules is mostly from half a line to a line. Ordinary corallites of two kinds — large and small. Large corallites, polygonal or sub- polygonal, from i-iooth to i-8oth inch in diameter, their walls amalgamated with one another, and moderately thickened as they approach the surface. Small corallites moderately but not excessively numerous, intercalated in the intervals between the large tubes, variable in size and shape, but always angular or sub-angular. A variable, but often considerable, number of minute thick-walled circular tubuli (" spiniform corallites ") developed between the normal corallites. Large corallites with comparatively few and remote tabulce ; small corallites with numerous close-set tabulae ; all the tabulae complete and approximately horizontal. Obs. — This well-marked species — the identification of which with M. maiiwmlata, D'Orb., will be subsequently discussed — resembles M. frondosa, D'Orb., M. molesta, Nich., and M. Dawsoni, Nich., in being normally frondescent (PI. VL fig. i), and in consisting of two strata of corallites which diverge in opposite directions, and nearly at right angles, from a median plane, which may be considered as dividing the corallum into two leaf-like halves. This median plane, however, is an Ima- ginary one, not marked by any mesial calcareous lamina ; so that, In this respect, the structure of the corallum differs from what we shall see to exist In M. frondosa. The calices are io6 THE GENUS MONTICULIPORA. thin-walled and polygonal, arid interspersed amongst them are the small angular or sub-angular apertures of the interstitial corallites (PI. VI. fig. \c), the number of which varies much in different specimens, and which are sometimes almost want- ing. The surface always exhibits " monticules," though the extent to which these are developed varies greatly in different examples. In some forms (PI. VI. fig. \a) the monticules are low and rounded, and, though quite recognisable, are certainly not striking features in the corallum. In other specimens, proved by microscopical examination to be identical with the preceding, the monticules are conical, or at other times elon- gated and compressed, in either case rising conspicuously above the general surface (PI. VI. fig. \b). As regards the minute structure, the appearances presented by tangential sections vary according to the depth below the surface at which these may be taken. In sections passing just below the actual surface (PI. VI. figs. \d and i^-), the corallites are seen to be moderately thick-walled, and divisible into a series of larg^e tubes and one of small tubes. The laro-e coral- lites are surrounded each by its own ring of laminated scleren- chyma, but they are nevertheless apparently fused with one another at the points where they come in contact. Their form is sub-polygonal, and all the interspaces left between them are occupied by much smaller angular or sub-angular corallites. Intercalated in the thickened walls of the corallites there is, also, a quite considerable number of minute circular, darkly- outlined hollow tubules or " spiniform corallites," the termina- tions of which have not been observed by me. In tangential sections taken at a slightly deeper level than the preceding (PI. VI. fig. i/), the appearances to be observed are somewhat different to those above described. The walls of the corallites are now reduced in thickness, causing their cavities to be proportionately increased in size. Hence the large corallites appear to be of somewhat larger size, and more strikingly polygonal, while the dimensions of the small tubes are similarly increased, and the number of the " spini- SUB-GENUS HETEROTRYPA. 107 form corallites " has notably diminished, showing that these latter do not extend to great depths below the surface. I have not succeeded in definitely recognising the " monti- cules " in tangential sections, which may be taken as showing that, on the whole, they do not differ materially in structure from the bulk of the corallum. Sometimes, certainly, the tubes of which they are composed look a little larger than the average ; but this may very possibly be an illusory appearance, and may be due to their greater nearness to the eye of the observer. In other cases, beyond a doubt, many of the tubes which are present in the monticules are below the average size. Vertical sections, taken at right angles to the plane of the frond (PI. VI. fig. i^), show, as before rem.arked, that the corallites of the opposed sides of the corallum do not spring from a definite mesial lamina, but simply diverge from one another at their bases. At first slightly oblique and thin- walled, they almost immediately bend outwards, their walls at the same time being moderately thickened by a deposit of light-coloured sclerenchyma, and they are then continued nearly at right angles to the surface on which they ultimately open. Sections of this kind show that all the tabulae are com- plete and approximately horizontal ; but there is a marked difference in the tabulation of the large and small corallites respectively, the tabulse of the former being few and remote, while in the latter they are numerous and close set. There is no doubt that the normal form of the corallum in this species is that of a flattened undulating frond ; but I possess one large and massive specimen, some three inches in height by four in width, and two inches in thickness, which has all the superficial characters of this form, and most of its microscopic features. It differs, in fact, from the normal examples of this species in no other peculiarity except that the number of the small interstitial corallites is markedly reduced, while its monticules are, perhaps, rather more pro- nounced than is common in this type. So far, however, as I loS THE GENUS MONTICULIPORA. can judge from an examination of thin sections of this single specimen, I am disposed to regard it as a mere variety of the present species. Before leaving this form, It Is necessary to inquire briefly what erounds there are for reo-arding; it as the M. inamiindata of D'Orbigny ; and on this point, I regret to say, there is but little that can lead in the meanwhile to any positive conclu- sions. Good observers, indeed, are of opinion that the pres- ent form is really the ]\I. frondosa of D'Orbigny, and that the form which I shall describe afterwards under the name of M. niolcsta is the true J/, maimnnlata ; and though I myself decidedly differ from this view of the subject, I not only can- not pretend to establish my owm view beyond controversy, but I am oblifjed to admit that there exists much o-round for a legitimate difference of opinion on this point. The diffi- culties which environ this question arise from the fact that there are at least three, possibly four, distinct structural types of Moiiticulipora which occur in the Cincinnati Group of Ohio, all of which are more or less Identical In external characters, and any one of which might therefore be supposed to be the genuine AI. viainnuilata of D'Orbigny, and of Milne- Edwards and Haime. These three or four types are the following : — {a) The form which I have here described as J/, maninui- lata, which grows in thin undulated fronds, and has its sur- face covered with monticules, which are sometimes low and rounded, sometimes conical, sometimes elongated. {b) The form which I have spoken of above as probably a variety of the preceding, which it resembles generally in Its microscopical characters, except that it has a much smaller number of interstitial corallites. In its mode of growth It is massive, and Its monticules are pronounced and conical or elongated. (z.) Chaidcs itiidulatiis, Nicholson, Geol. Mag. Dec. ii., vol. ii. p. 176, 1S75. ,, i//idi//ati/s, Nicholson, Rep. on the Pal. of Ontario, 1875, PP- 1°? 33; PI. IV. fig. I. j\[oitticiilipora [Monotrypa) midiilata, Nicholson, Pal. Tabulate Corals, p. 321, PI. XIV. figs. 3 and 4, 1 87 9. Spec. Char.- — Corallum forming large, lobed or laterally in- dented masses ; or occurring as smaller hemispherical or spher- oidal masses, of from half an inch to more than an inch in diameter, Corallites uniformly thin-walled, angular, and prismatic in shape, sub-equal in size, the average tubes vary- ing from one-fifth or one-sixth of a line up to a quarter of a line or rather more. The bulk of the corallum is made up of corallites of the smaller of the above dimensions, while the slightly larger tubes form clusters of six or more, which appear on the surface as patches or " monticules," which are but faintly or not at all elevated above the general level. Small corallites are also often present at the angles of junction of the larger tubes, but they may be wanting : they are never a con- spicuous feature, and their internal structure is the same as that of the normal corallites, Tabuke horizontal, complete, remote, equally distributed through all the tubes of the colony, and often placed at corresponding levels in contiguous tubes, so that the corallum breaks up Into a series of concentric strata. Obs. — The type of this species is a large and massive coral, which occurs In the Trenton Limestone of Canada. With this I formerly associated certain large and lobate IlIoiitictLlipoi^cE from the Cincinnati Group of Ohio and the Hudson River for- SUB- GENUS MONOTRYTA. 171 mation of Canada, similar in form to some of those included by- Hall under the name of Chcrtctcs lycopcrdou, Say (Geol. Mag., Dec. ii., vol. ii. p. 177). I have now had the opportunity of examining these latter forms microscopically, and I find that I was in error in associating- these with the Trenton Limestone Fiy. 32. — ]\IonlictiIipora {Monotrypa) midiilata, Nicli., froin the Trenton Limestone of Canada. A, Part of the type-specimen, in outline, of the natural size; B, Tangential section, enlarged eighteen times, showing the thin-walled angular corallites ; c. Part of a longitudinal section, similarly enlarged, showing the wavy walls and the sparse taljulx. species. On the other hand, a minute examination of the corals of the Hudson River Group of Canada, which have commonly been spoken of as " puff-ball varieties of Stcuopora fibrosa',' and which I used to regard [op. jam cif., p. 176) as a mere variety of AT. pctropolitana, Pand., has shown me that these are in all essential respects entirely identical in internal structure with the AL iindulata of the Trenton Limestone, from which they differ principally in their smaller size and 172 THE GENUS MONTICULIPORA. hemispherical or spheroidal shape (fig. 33, a). I have figured thill sections of both for comparison. Tangential sections of both the Trenton Limestone and Hudson River Group examples of M. 7indulata (figs. 32, 33, b) show the corallites to be strikingly thin-walled and markedly angular, while, except for the occasional presence of a cluster of somewhat extra-sized tubes, their dimensions are very uniform. Small corallites are present, not unfrequently, at the angles of junction of the large tubes ; but they are obviously young tubes, and do not form part of a series of special corallites. That this view is correct is shown by their inconstant occur- rence, but is still more conclusively proved by vertical sections (fig. 32, c). These show that all the corallites — those forming the clusters as well as those composing the mass of the colony — are precisely similar in their structure, and are not divisible into a series with remote and one with crowded tabulae. All alike have thin, flexuous, often closely undulated walls, and in all alike the tabulae are delicate horizontal plates, situated at distances of from a quarter of a line to nearly a line. In fractured surfaces the tubes separate cleanly from one another, and their faces are seen to be crossed by numerous delicate transverse striae, corresponding with the undulations of their walls. In all the specimens I have examined there is, also, an evident periodicity of growth, tabulae being periodically de- veloped at corresponding levels in all the tubes, so that the entire corallum breaks up into concentric layers. As before remarked, I see no reason to doubt that the massive examples of ]\I. inidiilata from the Trenton Limestone are specifically identical with the smaller rounded masses which occur in the Hudson River Group; at the same time that I re- gard the former as the type of the species. The chief differ- ences between these two forms may be advantageously added here, their chief points of agreement having been previously noticed. The typical exahiple from the Trenton Limestone (fig. 32, a) is a large undulated and folded mass, with a maxi- mum diameter of about four inches, and a heifrht of about S UB- GENUS MONO TR YPA . 173 two inches, the calice-bearing upper surface being nearly flat. Tangential sections (fig. 32, r.) show that the ordinary corallites have an average diameter of from i-7oth to i-5oth inch, while at the angles of junction of these are often small angular tubes of I -300th inch diameter or less. The angles of junction of adjoining corallites are often slightly thickened, though never conspicuously so, and the corallites are otherwise uniformly thin-walled. On the other hand, the specimens from the Hudson River Group (fig. 33, a) form rounded or irregularly spheroidal Fig- 33- — A, A specimen of MonticuHpora iimiidata, Nicli., from tlie Hudson River Group of Canada, of the natural size, partly broken away on one side ; B, Tangential section of the same, enlarged eighteen times ; c, Vertical section of the same, similarly enlarged, show- ing the wavy walls and the remote tabula;. masses, generally from an inch to an inch and a half in dia- meter, and sometimes growing round the stem of a Crinoid. None of my specimens exhibit an unworn surface. Tangen- tial sections (fig. 'i,'^, b) show that the ordinary corallites have an average diameter of from i-QOth to i-6oth of an inch, and that they are therefore, upon the whole, slightly smaller In their dimensions than is the case with the corresponding corallites in the Trenton Limestone specimens. A consider- able number of small angular corallites, of an average diameter of I -300th inch, are wedged in at the corners of the larger tubes. As a rule, the corallites in tangential sections exhibit the same thin-walled and delicate structure that Is characteristic of the Trenton Limestone examples ; but In some parts of these sections (probably the parts nearest the original surface) the walls become decidedly thickened, and very conspicuous nodes 174 THE GENUS MONTICULIEORA. are developed at the angles of junction of adjoining tubes. Longitudinal sections (fig. 2^^, c) show no appreciable differ- ences as compared with corresponding sections of the specimens from the Trenton Limestone. Upon the whole, I am disposed to think that there is not sufficient ground for regarding the Hudson River Group specimens as even a permanent variety of the type-form of M. 7uidulata. Foruiation and Locality, — Rare in the Trenton Limestone of Peterboro', Ontario. Common (the "puff-ball variety") in the Hudson River Group of Toronto, Weston, and other localities in Ontario. Monticulipora (Monotrypa) Winteri, Nich. (Fig. 34-) ATonticiilipora IVi/ifcri, Nicholson, Pal. Tab. Corals, p. 323, PI. XIII. figs. 5, 5^7, and PI. XIV. figs. 2, 2a, iSig. Spec. Char. — Corallum when young, discoid and concavo- convex ; when adult, hemispherical or sub-globular. Young examples may be three or four lines in diameter, and less than two lines in greatest height ; while fully grown specimens may be more than an inch and a half in diameter, and more than an Inch in height. The base is free, or attached to some foreiofn body at one point, and it is either flat or concave, and is covered by a concentrically striated epithecal membrane. The corallites radiate from the base and open upon the upper sur- face by thin-walled polygonal calices. The surface shows clusters of slightly extra-sized corallites, which are only occa- sionally elevated to form low " monticules." The corallites are all uniformly thin-walled, strictly angular or prismatic in form, and sub-equal in size, averaging a quarter of a line in diameter. In internal structure they are all alike, all being provided with delicate, remote, complete, and horizontal tabuloe. S UB- GENUS MONO TR YPA. 175 Obs. — Examples of this species are of common occurrence in the Devonian Limestone of Gerolstein, and are so entirely similar in form (fig-. 34, a) to the Lower Silurian I\I. pctropoli- Fig. 34. — Alonticiilipora M'intcri, Nich., Devonian, Gerolstein, Eifel. A, A specimen, of the natural size, viewed in profile; B, Base of the same specimen, of the natural size; C, Part of a tangential section of the same, enlarged eighteen times ; D, Part of a vertical section, showing the remote tabulre, similarly enlarged. tana, Panel, that a merely macroscopic examination would almost certainly have led to their being identified with the latter form. A microscopic examination, however, shows that their structure is that of Monotrypa, and not that of Diplotrypa, all the tubes alike being essentially similar in their internal characters. Tangential sections (fig. 34, c) show that the tubes are essentially uniform in size, a few slightly larger ones form- ing scattered clusters, while such intercalated small ones as are present are obviously merely young corallites. All the tubes also are bounded by very delicate walls, and are regular, angular, and prismatic. Vertical sections (fig. 34, d) show a complete identity in structure in all the corallites, the tabuke being complete and remote, and sometimes placed at corre- sponding levels in many of the tubes. Recently, Dr Daniel CEhlert, of Laval, has been good enough to send me a number of specimens, from the Inferior Devonian deposits of La Baconnicre, Laval, which agree precisely both in their external characters and their minute structure with examples of I\I. Wiiitcri from the Eifel. With regard to the Eifel specimens, Dr Steinmann, whose 176 THE GENUS MONTICULIPORA. authority upon such a subject is justly of great weight, has suggested (N. Jahrb. fiir Min., Geo!., unci Pal., 1880, p. 438) that the species is really the same as the previously described Favositcs fibroglobos2Ls of Ouenstedt, which occurs at the same locality (Gees, near Gerolstein). In a careful examination, however, of both my German and French specimens, carried on both externally and by means of microscopic sections, I have been quite unable to detect any evidence of the existence of mural pores. I do not in the least desire to call in question the validity of Professor Ouenstedt's species ; nor, though I un- fortunately have not at this moment access to its description, do I question its external resemblance to ]\I. IVinteri. It is, however, quite clear that in a point of this kind no reliance can be placed upon anything of the nature of external simili- tude, however close, or, in fact, upon anything but identity of internal structure as demonstrated by the examination of thin sections. Now, I find that in the comparatively small collec- tion which I myself made at Gees, three quite distinct forms are really present, all so like each other that, prior to micro- scopic examination, I had unhesitatingly placed them together as belonging beyond doubt to the same species. Thin sections of these, however, show that these three forms are all widely different from one another in internal structure. One of them is the form here described under the name of iMonticidipora W inter i; another is a true FisttLlipora, as that genus is de- fined by M'Coy ; and the third is a genuine Alveolites, and is provided with numerous and well-marked mural pores. The form described by Ouenstedt under the name of Favosites fibroglobos2is (Petref Deutschlands, Bd. VI. S. 15, Taf 143) is one that, as previously remarked, I am not acquainted with ; but, so far as its external form is concerned, it might quite well be any one of the three forms which I have just mentioned, or it might be a quite distinct form.^ At any rate, the facts ' In this connection I may point out a source of fallacy in a number of the speci- mens of the Eifel corals. In many of these the fossil is largely impregnated with globular grains of peroxide of iron, and these in thin sections often simulate mural SUB- GENUS MONOTRYPA. 177 which I have here brought forward entitle me to claim that it is not in the meanwhile proved that my M. Winteri is identi- cal with Favosites jibroglobosus, Ouenstedt. Not being myself in the position to examine microscopic sections of the latter form, I do not feel able to deny that the two may prove to be really the same ; but I do not think the evidence would at present be sufficient to demonstrate this. In any case, I may point out that the validity of the section Monotrypa will not be affected by the ultimate fate of M. Winteri, since the type of this section is the M. nndtilata of the Trenton Limestone. From AI. ^tnd^Uata the present species is distinguished by its concavo-convex or regularly hemispherical form, by the more rapid intercalation of the new tubes, and by the greater abundance of the tabulae, while it never attains the dimensions, or assumes the lobate habit, of the former. I have named the species in honour of Herr Winter of Ger- olstein, from whom I received much friendly assistance while collectinof in the Eifel. Formation and Locality. — Not uncommon in the Devonian of Gees, near Gerolstein, Eifel. Also not uncommon in the Inferior Devonian deposits of La Baconniere, Laval. (Coll. Dr Daniel CEhlert.) Monticulipora (Monotrypa) irregularis, Ulrirli. (Fig. 35-) CJicctetes irregularis, Ulrich, Journ. Cincinnati, Soc. Nat. Hist., 1879, ?'■ XII. figs. 10-10/'. Spec. Char. — Corallum of small size (generally about three- quarters of an inch in diameter), apparently free, and approxi- mately spheroidal in shape, the surface being usually covered with irregular and well-marked nodulatlons. No monticules pores, especially where (from their soft and friable nature) they have been worn away in the process of preparing thin sections. Their true nature is, however, at once recognised when it is seen that they are just as conspicuous in tangential as in longitudinal sections. 1 78 THE GENUS MONTTCULIPORA. or defined groups of either large or small corallites. Corallites of one kind only, thin-walled, polygonal in shape, radiating outwards from a basal point towards all parts of the surface. Average diameter of the corallites from i-iooth to i-8oth inch, a few small corallites being occasionally present, but there being no interstitial tubuli. Tabulae almost obsolete, though complete transverse partitions are occasionally developed in certain regions, and generally at corresponding levels in con- tiguous tubes. Obs. — This singular species has been excellently described by Mr E. O. Ulrich {Joe. cit. supra), and I am able to corrob- orate most of his observations from a careful investigation of specimens for myself. Its small size, apparently free habit, and nodulated surface (fig. 35, a) are w^ell-marked external Fig. 35. — MonticiiUpora irregularis, Ulrich, from the Cincinnati Group of Oliio. A, A speci- men of the natural size ; B, Tangential section of the same, enlarged eighteen times ; c, Vertical section of a few of the tul^ies of the same, similarly enlarged, showing a couple of tabula;. characters, though, according to Ulrich, the surface may be nearly smooth. In internal structure, this species belongs to that group of Montiailipor^E which I have associated together under the name of Mono try pa. In tangential sections (fig. 35, b) the corallites are seen to be of one kind only, tolerably equal in point of size, thin-walled, polygonal, and wholly with- out minute interstitial tubules of any kind. In longitudinal sections (fig. 35, c) the tubes are seen to preserve the same thin-walled character throughout, the walls being slightly flexuous, but not sharply undulated. In the specimens that SUB-GENUS MONOTRYPA. 179 I have examined, the tubes seem to radiate from a point near the base; but Mr Ulrich describes the normal arrange- ment to be that the tubes " radiate from various centres, which correspond in number to that of the prominent nodules ob- served on the surface." This observer also states that, after examining transparent sections, he had been unable to detect any tabulae ; and this observation is so far correct that tabulae are certainly totally wanting throughout a great part of the corallum. I find, however, that there is commonly a single tabula (sometimes two or three) developed in many of the tubes at a short distance inwards from their termination on the surface, and that these tabulae are commonly placed at corresponding levels in contiguous tubes. An occasional tabula may also be observed in the interior of the corallum. M. ii^rcgtilaris, Ulrich, is most nearly allied in internal structure to the smaller types of AL tmdulata, Nich. (which may possibly constitute a separate species), but it is suffici- ently distinguished by its external characters, and its much more limited development of tabulae. Horiso7t and Locality. — Cincinnati Group, Ohio (according to Ulrich, it marks an horizon of about 550 feet above low- water mark in the Ohio River, Cincinnati). Monticulipora (Monotrypa) quadrata, Rominger. (Fig. 36.) Chcetetcs quadratus, Rominger, Proc. Acad. Nat. Sci. Phil., 1866, p. 115. ,, rhombicus, Nicholson, Quart. Journ. Geol. Soc, vol. xxx. p. 507, PI. XXIX. figs, ii-ii/^, 1874. Pal. Ohio, vol. ii. p. 201, PI. XXI. figs. 12, 12^, 1875. Ann. Nat. Hist., ser. 4, vol. xviii. p. 86, PI. V. figs, i-i/;, 1876. {Non Diannlifcs rJiombicus, Dybowski, Die Ch^etetiden, p. 33, 1877.) Spec. Char. — Corallum dendroid, of cylindrical or sub- cylindrical branches, which vary from rather more than two up to five lines in diameter, and often terminate in rounded or bulbous extremities. Corallites primitively thin - walled, i8o THE GENUS MONTICULIPORA. and becoming slightly thickened towards their mouths, but always retaining their original boundary-lines. They are all of one kind, sub-equal, from i-yoth to i-8oth inch in diameter, being rhomboidal in shape in the centre of the branches, but often becoming pentagonal as they approach the surface. Calices often polygonal, but usually in parts obliquely rhombic, and arranged in regular diagonal rows, the direction of which changes within short distances, thus communicating to the surface a characteristic aspect. No monticules or maculae are present, and the lips of the calices are thin. Tabulae appear to be wanting, or to be very sparingly developed, in the axial reeion of the corallum ; but there exists a considerable number of complete, straight, or slightly curved tabulae in the outer thickened portion of the corallites, the tabulation of all the tubes being alike. Obs. — Superficially, this species is readily distinguished from the other dendroid species of Alontiailipom by the commonly rhombic or diamond-shaped form of many of the calices, these openings being then arranged in curved diagonal lines, which cross each other obliquely. Even when the calices are simply polygonal, as is sometimes the case, over large parts or over the whole of a given specimen, this characteristic appearance may still usually be recognised by an examination of the weathered ends of the stems where the invariably rhomboidal tubes of the axial rcQfion are brouQ-ht into view. The re- maining superficial characters that are of the most importance are the want of marked thickening in the edges of the calices, and the total absence of small interstitial corallites, as well as of monticules or of groups of either large or small tubes. As regards its internal structure, M. qnadj'aia, Rominger, exhibits characters of such marked peculiarity, that there is no other species of the genus, so far as I know, with which it requires to be compared. In the axis of the branches, the corallites are always provided with very thin and delicate walls, and have no tabulae, or hardly any. In this region, also, as shown by the central part of a transverse section (fig. 36, d). SUB-GENUS MONOTRYPA. they exhibit their most highly characteristic shape, being strictly rhombic or square, and being arranged in regularly f'g- 36. — A, A fragment of Monliculipora quadra ta, Rominger, from the Cincinnati Group of Ohio, of the natural size ; B, A tangential section of the same, passing just below the calices, enlarged eighteen times ; C. Part of the preceding section, enlarged fifty times, show- ing the structure of the walls of the corallites ; D, Part of the central area of a transverse section, showing the peculiar rhombic form of the tubes in this region, enlarged eighteen times ; E, Part of a vertical section, enlarged eighteen times. decussating oblique lines. Thin as their walls are here, there is usually a more or less conspicuous nodal enlargement at each of the angles of junction of the corallites. The cavities of the tubes are filled with transparent calcite, and each has its rhomboidal area very distinctly and regularly divided into four equal triangles by a cruciform divisional line. These divisional lines in the interior of the tubes are perfectly regu- lar in their arrangement, and are quite uniform in their direc- tion in each specimen : they therefore give rise to a second, fainter, double series of diagonal lines, which intersect the ,82 THE GENUS MONTICULIPORA. more strongly marked series of diagonals formed by the walls of the tubes themselves. Similar, but less conspicuous and less regular, divisional lines are visible in the calcite which fills the tubes of the corallites in many species of Monticuli- pora and in Constellaria ; but I have been unable to satisfy myself as to the true cause of this phenomenon. In the outer portion of the course of the corallites, when they have turned out towards the surface, their walls always become recognisably thickened, and they often, though not always, lose their quad- rangular form, and become pentagonal or hexagonal (fig. 36, B and c). The thickening of the walls of the tubes, however, does not go so far as to entirely obliterate the original dis- tinctness of the corallites. On the contrary, the primitive boundary lines between adjoining tubes can always be readily made out (fig. 36, d) ; and along these lines the corallites readily separate from one another. Not only are all the corallites of one kind, in the sense that there are no " interstitial corallites" of any kind, but long sections show that the tabulation of all the tubes is the same. All, namely, possess a moderate number of strong and com- plete tabulae, which are developed in the curved portion of the tubes just below the surface. Many of the tabulae are slightly curved, either convex or concave, and they often join with one another ; but others are straight. Hoi'izou and Locality. — Cincinnati Group, Cincinnati, Ohio. Monticulipora (Monotrypa) clavacoidea, James. (i^'ig- 37-) Chcetetes davacoideus, James, Cat. Lower Sil. Foss., 1871. (Named but not described.) „ ,, James, Cat. Lower Sil. Foss., 1875, p. i. Spec. Char. — Corallum forming a crust, which is attached by the whole of its base to foreign objects, and is composed of corallites which are uniformly disposed at right angles to the SUB-GENUS MONOTRYPA. 183 surface of attachment. The species seems to be constantly parasitic upon the tapering ends of minute species of Orthocera- tites, and the coralhim is constantly cylindrical in form, some- times becoming slightly fusiform or clavate. In general the Orthoceras has disappeared, and the space which it originally occupied is filled up with calcite or with the matrix, or may be simply hollow. Corallites thin - walled, polygonal in shape, and generally nearly equal in point of size, their long diameter being, as a rule, between i-iooth inch on the one hand, and i-8oth inch on the other hand. Surface either smooth, or sometimes showing groups of corallites of rather larger size than the average, these groups being elevated to form low and ill- defined tubercles. Tabulae absent throughout the greater part of the tubes, but apparently not wholly wanting in any given section, an occasional complete partition being developed here and there in the deeper parts of the corallum, or, still more frequently, close to the mouths of the tubes. Obs. — The external form and superficial characters of ]\L clavacoidea have been accurately described by Mr U. P. James (Cat. Lower Sil. Foss., 1875), to whose kindness I am indebted for specimens of this, as of many other types. I am not aware, however, that its microscopic structure has hitherto been noted. In its mode of growth and its resulting form, M. clavacoidea is quite peculiar. The colony is never large, its length vary- ino" from half an inch to at least two inches, and its width from three or four to eight lines ; while its form is constantly cyl- indrical, or bluntly fusiform, or somewhat clavate (fig, 37, a). This form is in all cases due to the fact that the corallites at all points of the corallum spring perpendicularly from a central elongated cone, one end of which is closed, and is consequently usually completely covered with the tubes, while the other end is open. Sometimes both ends of the colony are open. The conical space in the centre of the corallum is, in all my speci- mens, filled with calcite or with the surrounding matrix, or is simply, hollow ; but I entertain no doubt that Mr James is 1 84 THE GENUS MONTICULIPOKA. correct In his statement that the colony really grew parasitically upon the closed and tapering extremities of the dead shells of \r^\ ^,^^^^'S^ fG Fig. 37. — Monticiilipora- davacoidea, James. A, An average specimen of the natural size; B, Part of the surface of the same, enlarged eighteen times ; c. Portion of a tangential section, enlarged eighteen times ; D, Part of a transverse section of the same, show- ing the corallites radiating outwards from the foreign body to which they are attached inferiorly, enlarged seven times; E, Part of the same section, enlarged eighteen times, showing the uniformly thin-walled corallites, and their few and lemote tabulae. From the Cincinnati Group, Cincinnati, Ohio. OrtJiocerata. This is, therefore, a curious instance of the persistence with which a particular species attaches itself to some particular object, never seeming to fix itself upon any other. Apart from its very peculiar and apparently constant form and mode of growth, M. clavacoidca is readily distinguished by its minute structure. Tangential sections (fig. 37, c) show that the corallites are uniformly thin-walled and polygonal, slight nodes being often formed at the angles of junction of contigu- ous tubes. Their size is very uniform, though groups of coral- lites of slightly larger dimensions than the rest are certainly occasionally developed. In any case, there exists no series SUB- GENUS MONOTRYPA. 185 of small interstitial tubes. Vertical sections (fig. 37, d and e) show that there is no difference whatever in structure between any one set of corallites and any other. In none are the walls thickened towards the surface, but they are uniformly thin throughout, and are often slightly wavy. The course of the tubes is straight, there being no curvature near their bases, and they increase in number in passing outwards by the inter- polation of fresh tubes. In a great number of the tubes no tabulae exist at all ; but an occasional tabula is sometimes de- veloped near the mouth of the tube, or at some depth below the surface. In internal structure, M. clavacoidea, James, is most nearly allied to M. irregularis, Ulrich ; but the form of the corallum and the mode of growth afford a sufficient means of separation. Horizon and Locality .—Q.\\\(:\\\W2X\ Group, Cincinnati, Ohio. (Coll. U. P. James.) Monticulipora (Monotrypa) calceola. Miller and Dyer. (PI. I. figs, z-y.) Alonticulipora calceola, Miller and Dyer, Journ. Cincinnati Soc. Nat. Hist., vol. i. 1878. Spec. Char. — Corallum free (?), of small size, varying from less than one line up to more than six lines in diameter, helicoid in shape, and traversed by a horn - shaped cavity, which opens upon the exterior by a well-marked circular aper- ture, the inner lining of which shows encircling striae, and which varies from half a line or less up to more than two lines in diameter. Surface smooth, or covered with low rounded tuber- osities. Calices approximately equal, thin-walled, and poly- gonal in shape. Corallites radiating from the outer surface of the afore-mentioned central tube to open in a nearly rectilinear manner upon all points of the surface except the external aper- ture of the central tube. Corallites polygonal, thin-walled, from I -90th to I -70th inch in diameter, very minute angular or 1 86 THE GENUS MONTICULIPORA. rounded tubes being situated at their angles of junction. Tab- ulae fairly developed, complete and horizontal, increasing in number as the mouths of the tubes are approached. Obs. — This very singular species was originally described by Messrs Miller and Dyer {Joe. cit.) ; but I have, unfortunate- ly, not been able to refer to the original paper. Its peculiar helicoidal shape (PI. I. figs. 3, 3cr), and the fact of its being built round a curved central tube which opens externally by a round aperture, would alone distinguish the species, quite apart from its internal characters. I do not know what view was adopted by Messrs Miller and Dyer as to the origin of this very unusual and apparently constant form, but I gather from a letter from Mr Nickles, of Cincinnati, that after study- ing the numerous specimens in his extensive collection, he is disposed to regard its form as something peculiar to itself, and not as due to the fact that it has grown round some foreign organism. In such thin sections as I have made, it seems certain that the central horn - like cavity is lined by a well- defined calcareous layer (PI. I. fig. y), the structure of which seems to be quite distinct from that of the corallites them- selves; and I was therefore at first disposed to regard the col- ony as parasitic upon some such foreign object as a Tubicolar Annelide, to which fact its peculiar forn^i might be ascribed. Mr Nickles, however, is of the opinion that this calcareous lining of the tube is really the epitheca of the colony ; and as his opportunities of observation have been much greater than mine, it is quite possible, and indeed probable, that he is right in this opinion. Certainly, the fact that specimens no bigger than the head of a moderate-sized pin should show the same peculiar form and the same strange central tube as occur in fully-grown examples, would militate very strongly against the view that the spiral tube can be foreign to the corallum. It reminds one of the "worm-like body" of Plciirodictyiini, though it is not possible to assert that the two structures are the same. In external characters the calices of M. calccola are thin- SUB-GENUS MONOTRYPA. 187 walled and polygonal, and of tolerably equal dimensions (PI. I. fig. 3<^). As regards internal structure, tangential sections (PI. I. figs. 3 Upper view of a specimen oi MonticuUpora Sehvynii, var. Jiospitalis, Nich., from the Cincinnati formation of Waynesville, Ohio, of the natural size : the coraUum is attached by its base to the shell of Strophoniena nutans, James. K, Side view of the same specimen, of the natural size, c, Tangential section of the same, enlarged eighteen times. D, Vertical section of the same, enlarged eighteen times. corallites, the former being oval or circular in shape, and varying from i-5oth to i-7oth inch in diameter, each showing an excentrically perforated tabula. The small corallites are numerous, sub-angular, and wedged in between all the larger tubes, occasionally being aggregated into star-shaped groups or " maculae." Besides the normal two kinds of corallites, a considerable number of thick-walled hollow spines (" spiniform corallites ") may be observed, which I have not detected as present in the examples from the Trenton Limestone. Vertical sections (fig. 45, d) show the same marked differ- ence in the tabulation of the large and small corallites as has been previously noticed in the type-form, with some differ- SUB- GENUS PRASOrORA. 2ti ences. The large tubes are always doubly tabulate, one set of tabulae forming a series of large lenticular vesicles, the con- vex sides of which are directed inwards towards the centre of the visceral chambers, while the remaining tabulae are horizon- tal and remote, and extend from the lateral wall of the coral- lite to the inner margin of the above-mentioned vesicles. In some of the tubes we may occasionally notice the convex tabulae to form isolated vesicles, as they usually do in the specimens from the Trenton Limestone ; but they are more commonly so apposed to one another as to form vertical rows of lenticular cells, the inner margins of which unite so as to constitute an apparent median septum to the corallite. The small corallites are uniformly furnished with numerous com- plete, horizontal tabulae. Upon the whole, I have little doubt that the specimens now described from the Cincinnati Group of Ohio are not specifically separable from the true M. Sel- wynii of the Trenton Limestone, In form and general aspect, M. Sclwynii closely resembles such types 2S M . petropolitana , Pand., or A4. Whiteaveszi, Nich. In its internal structure, however, it is clearly allied to quite another group of types — namely, to such forms as M. Cincin- natiensis, James, M. froiidosa, D'Orb., Jll. Ncivberjyi, Nich,, and M. molesta, Nich., all of which agree with Prasopora Grayci", Nich. and Eth. jun., in the possession of a peculiarly modified structure of the tabulae of the larger corallites. In fact, M. Selwynii is more nearly allied to Prasopora Grayce, Nich. and Eth. jun., than to any other type known to me, and it must be regarded as a member of the sub-genus Prasopora, as I have previously defined it. In its purely specific char- acters, however, it is so far distinct that it requires no close comparison with any other form with which I am acquainted. Horizon and Locality. — In the Trenton Limestone of Peter- boro', Ontario (the type-form). In the Cincinnati Formation of Waynesville, Ohio (var. hospitalis). 212 THE GENUS MONTICULIPORA. Monticulipora (Prasopora) Newberryi, Nicholson. (PI. IV. figs, i-i^.) Chcztetes Neivberryi^ Nicholson, Palaeontology of Ohio, vol. ii. p. 212, PI. XXII. figs. 4, 4^-, 1875. Spec. Char. — Corallum forming thin, sub-circular or semi- circular expansions, which may be from ten lines to an inch or more in diameter, and have a thickness of about i-40th inch. Judging from thin sections, the corallum does not seem to have been parasitic, but to have possessed a thin basal epitheca. Surface exhibiting groups of corallites which are slightly larger than the normal tubes, but which do not form distinctly raised tubercles. Calices thin-walled and polygonal, often apparently without small interstitial apertures, though these can be occasionally detected, and must be generally present. Average diameter of the ordinary corallites about I -70th inch or rather more. As seen in sections, the large corallites are oval, only touching each other at limited points, and having the interspaces between them filled up by numer- ous smaller and irregularly shaped interstitial corallites. The large corallites possess imperfect tabulse, which form a series of convex vesicles on one side of the tube, the other side being open and non-tabulate. Small interstitial corallites with numerous close-set straight tabulae. Obs. — My original diagnosis of this species was founded only upon its external characters, and was principally errone- ous in the fact that I had not detected any interstitial tubuli — an error which may be excused, since large parts of the surface, when examined with a lens or with the microscope, really do not show any openings of the smaller corallites. In fact, when thus examined, the surface (PI. IV. fig. ib) is principally notice- able for the polygonal form, the thin walls, and the seemingly close contact of the calices. Nevertheless, thin sections prove conclusively that interstitial tubes are abundantly present ; and the most probable explanation of this apparent discrepancy SUB-GENUS PRASOPORA. 213 between the results of external and internal observation may be that the apertures of the small tubes on the surface are in general concealed by their overgrowth with a calcareous mem- brane. A few, however, of the minute openings of the inter- stitial tubes, may usually be detected in one part or another of the surface of the corallum by a sufficiently careful search with a one-inch objective. From the great thinness of the expanded corallum, it would naturally be supposed that the colony was parasitic upon foreign bodies ; and none of my specimens would disprove this supposition, as in all the upper surface alone is shown, and the under surface is buried in the matrix. Thin vertical sections, however, so far as I have seen, do not show any foreign body beneath the thin crust of corallites, but show that the under surface is covered with a thin epithecal membrane. The general form and surface-characters of this species are quite peculiar ; but the internal structure is even more dis- tinctive. Tangential sections (PI. IV. figs, i c and d) show that the corallum is composed of two distinct sets of tubes, which differ not only in size, but, very markedly, in their internal structure. The larger tubes, instead of showino; the polygonal form which they have at the actual surface, are oval in shape, and are therefore only in contact at very limited points of their circumference. They possess thin but quite well defined walls, and their tabuke are imperfect, appearing (in sections of this kind) as if perforated by crescentic apertures on one side. The interspaces left between the large tubes are occupied by a series of small corallites, which never completely isolate any single large corallite, and of which no more than a single row is ever present between any given pair of the large tubes. These small corallites are very variable in size, and are angular in their shape. In vertical sections (PI. IV. fig. \c), the differences between these two sets of tubes are very clearly marked;, quite apart from the difference in size. The large corallites are now seen to be furnished with purely unilateral tabulae, which are convex, with their convexities turned towards 2 14 THE GENUS MONTICULIPORA. the centre of the visceral chamber, and which form a row of lenticular vesicles on one side of the tube. The other side of the tube Is entirely free and open, and Is not crossed by any horizontal tabulae. On the other hand, the small tubes are furnished with numerous, close-set, complete, and horizontal tabulae. The species to which ]\I. Ncwberryi most nearly approaches In Internal structure Is III. Schvynii, NIch. The form of the corallum In the two species Is, however, entirely different, and there are Important structural differences as well. Thus, in M. Sehvynii the imperfect vesicular tabulae of the large coral- lltes are supplemented by a smaller number of horizontal tabulae, which cross the opposite side of the tubes ; while the small corallltes are aggregated at particular points into star-shaped maculae. Horizon and Locality. — Rare In the Cincinnati Group, Cin- cinnati, Ohio. (Coll. U. P. James.) 215 CHAPTER X. Sub-gen7is Peronopora, Nich., iSSr. I PROPOSE the sub-generic name of Peronopora for a peculiar group of Monticuliporoids in which the corallum is either laminar or encrustino-. Two distinct sets of coralhtes are present, distinguished by their size and internal structure. The large corallites are furnished with incomplete tabulae of the type of those found in the corresponding tubes of Praso- pora — that is to say, the tabulae form a series of lenticular vesicles on one side of each large corallite, these vesicles limiting an excentric lateral tube, which is crossed by a few complete horizontal plates. The small corallites are numerous, interspersed among the larger ones, sometimes partially aggre- gated into clusters, their tabulae being always numerous, close- set, horizontal, and complete. Spiniform corallites are usually largely developed, though occasionally apparently wanting {e.g., in Af. molesta, Nich.) The walls of the corallites are thickened and seemingly fused together in adjoining tubes, their primitively duplex character being entirely lost. Type of the group, M.frondosa, D'Orb. { = M. decipicns, Rom.) The species of this section are distinguished from those of all the other groups of Monticulipora, except Prasopora, by the peculiar structure of the tabulae of the large tubes. From Prasopora they are separated principally by the different form and mode of growth of the corallum, by the amalgamation of the walls of the tubes and their thickened character in 2i6 THE GENUS MONTICULIPORA. ' the vicinity of the surface, as well as, generally, by the abun- dance of their spiniform corallites. I propose to include under the head of Peronopo7'a the fol- lowing species of Monticnlipora — viz., M. frondosa, D'Orb. { = M. decipieiis, Rom.), AI. Cinciiznatiensis, James, M. violcsta, Nich., and M. ? Orto7ii, Nich., the last being an aberrant and ill-understood form ; and I subjoin descriptions of these as illustrating the structure of this peculiar group. Monticulipora (Peronopora) frondosa, D'Orbigny. (Figs. 46, 47, and PL V. figs. 4, 4a, and 5, 5i})iulatHS, E. and H., 104. Chcetetes jnujufnulattis, Nich., 104. Chcetetes Meeki, James, 127. Chcetetes moniliformis, Nich., 137. Chcetetes Newberryi, Nich., 212. Chcetetes nodulosiis, Nich., 116. Chcetetes O'Nealli, James, 1 1 8. Chcetetes Ortoni, Nich., 228. Chcetetes Pafideri, E. and H., 12. Chcetetes pavonia, E. and H., 195. Chcetetes petropolitanus, Nich., 160. Chcetetes pulchellus, E. and H., 188. Chcetetes pulchellus, Nich., 128. Chjetetes quadrangularis, Nich., 16. Chcetetes quadrattis, Rom., 179. Chsetetes radians, Fischer, 80. Chcetetes ramosus, E. and H., no. Clicetetes raniostis, Nich., no. Chcetetes rhombicns, Nich., 179. Chcetetes riigosus, E. and H., 113. Chcetetes sigillarioides, Nich., 118, ng. Chcetetes siibpulchelliis, Nich., 134. Chcetetes tuberciilatiis, E. and H., 200. 238 INDEX. C/u-E fetes tuviidits, E. and H., 120. Chatetes umhilatus, Nich., 170. Classification of Monticuliporoids, 90, lor ; according- to Dybowski, 19. " Coenenciiyma" of Monticuliporoids, 19. 49- Constellaria, Dana, 23, 30, 90, 97. Dekayia, E. and H., 30, 39, 98. Dianulites, Eichw., 2, 10, 11, 12, 13, 20, 155, 156. Dianulites, Uvb., 19, 20, 21, 22, 155, 156. Dianulites apiculatus, Eichw., 21. Dianulites detritus, Eichw., 12, 21. Dianulites elegantulus, Fr. Schmidt, 21. Dianulites fastigiatus, Eichw., 12, 21. Dianulites Haydenii, Dyb., 21, 22. Dianulites petropolitanus, Pand. (Dyb.), 21, 156; var. hexaporites, Pand., 21. Dianulites rhombicus, Dyb., 21, 179. Dianulites sulcatus, Dyb-, 21, 22. *Diplotrypa, Nich., 90, 100, loi, 155. * Diplotrypa calycula, James, 165. * Diplotrypa petropolitana, Pand., 156. * Diplotrypa Whiteavesii, Nich., 160. *Dittopora, Dyb., 20, 26, 102, 234. Favosites placenta, Rom., 96. Favosites tiimida, Port!., 120. Favosites turnida, M'Coy, 120. Favosites petropolitanus, Pand., 156. Favosites fibro-globosus, Ouenstedt, 176. Fistulipora, M'Coy, 22, 30, 90, 91-97. Fistulipora minor, M'Coy, 91, 92, 95. Fistulipora Canadensis, Bill., 94-96. Heterodictya, Nich., 88. Heterodictya gigantea, Nich., 89. Heterodictya pavonia, Ulrich, 195. Heteropora, Blainv., general charac- ters of, 63 ; relations of, to Monti- culipora, 73-77- Heteropora neozelanica, Busk, struc- ture of, 65-73. * Heterotrypa, Nich., 90, 100, loi, 103. * Heterotrypa Andrewsii, Nich., 128. * Heterotrypa Barrandi, Nich., 139. * Heterotrypa Dawsoni, Nich., 141. * Heterotrypa Girvanensis, Nich., 151. * Heterotrypa gracilis, James, 125. * Heterotrypa implicata, Ulrich, 147. * Heterotrypa Jamesi, Nich., 143. * Heterotrypa mammulata, D'Orb., 104. * Heterotrypa moniliformis, Nich., 137. * Heterotrypa nodulosa, Nich., 116. * Heterotrypa O'Nealli, James, 118. * Heterotrypa ramosa, D'Orb., no ; var. rugosa, E. and H., 113; var. Dalii, E. and H., 115. * Heterotrypa subpulchella, Nich., 134. * Heterotrypa Trentonensis, Nich., 149. * Heterotrypa tumida, Phill., 120; var. miliaria, Nich., 123. ■^ Heterotrypa Ulrichii, Nich., 131. Labechia, E. and H., 20, 26. Lichcnalia {?) calycula, James, 165. Maculae, 45. * Monticulipora, D'Orb., general history of, 1-29; general and comparative structure of, 30-55 ; general defini- tion of, 30 ; method of e.xamination of. 3i"33; form of corallum of, 33; structure of the walls of the coral- lites of, 36 ; surface-characters of, 44; spiniform corallites of, 45; di- morphism of the corallum of, 49; tabulae of, 51 ; alleged pseudo-septa of, 53 ; epithecal and opercular structures of, 54 ; development of, 56-62; affinities and zoological position of, 62-78 ; relations to Het- eropora, 73-77 ; to Chjetetes, 79 ; to Stenopora, 81 ; to Tetradium, 85 ; to Helioporidce, 85 ; to Cera- mopora, 86; to Heterodictya, 88; subdivisions of, 90-102; restricted definition of, 99 ; sub - genera of, 100-102. Monticulipora, Eichw., 13. Monticulipora, Dyb., 20, 25. Monticulipora eedilis, Eichw. (Dyb.), 25. * Monticulipora (Heterotrypa) Andrew- sii, Nich., 128. * Monticulipora (Heterotrypa) Barrandi, Nich., 139. Monticulipora Bowerbanki, E. and H., 9. * Monticulipora (Monotrypa) briarea, Nich., 198. * Monticulipora (Monotrypa) calceola. Miller and Dyer, 185. INDEX. 239 Monticulipora (Diplotrypa) calycula , James, 165. * Monticulipora (Peronopora) Cincin- natiensis, James, 226. * Monticulipora (Monotrypa) clavacoi- dea, James, 182. Monticulipora (?) crustulata, James, 27. * Monticulipora Dalii, E. and H., 115. * Monticulipora (Heterotrypa) Uawsoni, Nich., 141. MonticuUpora dccipicns, Rom., 222, 223. * Monticulipora (Monotrypa) discoidea, James, 193. Monticulipora Fletcheri, E. and H., 9, 132. Monticulipora Fletcheri, Nich., 131. * Monticulipora (Peronopora) frondosa, D'Orb., 216. * Monticulipora (Heterotrypa) Girvan- ensis, Nich., 151. * Monticulipora (Heterotrypa) gracilis, James, 25, 127. * Monticulipora (Prasopora) Grayae, Nich. and Eth. jun., 203. * Monticulipora (Heterotrypa) impli- cata, Ulrich, 147. Monticulipora inflata, De Kon., 15. * Monticulipora (Monotrypa) irregular- is, Ulrich, 177. * Monticulipora (Heterotrypa) Jamesi, Nich., 143. * Monticulipora (Heterotrypa) mammu- lata, D'Orb., 104. Monticulipora Meeki, James, 27, 127. * Monticulipora (Peronopora) molesta, Nich., 224. * Monticulipora (Heterotrypa) monili- formis, Nich., 137. * Monticulipora (Prasopora) Newberryi, Nich., 212. * Monticulipora (Heterotrypa) nodu- losa, Nich., 116. * Monticulipora (Heterotrypa) O'Nealli, James, 118. * Monticulipora (Peronopora) (.'') Ortoni, Nich., 228. * Monticulipora (Monotrypa) pavonia, D'Orb., 195. * Monticulipora (Monotrypa) petasifor- mis, Nich., 190. * Monticulipora (Diplotrypa) petropoli- tana, Pand., 156. * Monticulipora (Heterotrypa) pulchella, E. and H., 188. * Monticulipora (Monotrypa) quadrata, Rom., 179. * Monticulipora (Heterotrypa) ramosa, D'Orb., no; van rugosa, E. and H., 113; van Dalii, E. and H., 115. * Monticulipora rugosa, E. and H., 113. * Monticulipora (Prasopora) Selvvynii, Nich., 206; van hospitalis, Nich., 209. * Monticulipora (Heterotrypa) subpul- chella, Nich., 134. * Monticulipora (Heterotrypa) Trenton- ensis, Nich., 149. * Monticulipora (Monotrypa) tubercu- lata, E. and H., 200. * Monticulipora (Heterotrypa) tumida, Phill., 120; var. miliaria, Nich., 123. Monticulipora tumida, De Kon., 120. * Monticulipora (Heterotrypa) Ulrichii, Nich., I3n * Monticulipora (Monotrypa) undulata, Nich., 170. Monticulipora Wesenbergiana, Dyb., 25. * Monticulipora (Diplotrypa) Whitea- vesii, Nich., 160. * Monticulipora (Alonotrypa) Winteri, Nich., 174. Monticules, 44. * Monotrypa, Nich., 90, 100, 102, 168. * Monotrypa briarea, Nich., 198. * Monotrypa calceola. Miller and Dyer, 185. * Monotrypa clavacoidea, James, 182. * Monotrypa discoidea, James, 193. * Monotrypa irregularis, Ulrich, 177. * Monotrypa pavonia, D'Orb., 195. * Monotrypa petasiformis, Nich., 190. * Monotrypa pulchella, E. and H., 188. * Monotrypa quadrata, Rom., 179. * Monotrypa tuberculata, E. and H., 200. * Monotrypa undulata, Nich., 170. * Monotrypa Winteri, Nich., 174. Nebulipora, M'Coy, i, 2, 5, 15. Nebulipora explanata, M'Coy, 5. Nebulipora lens, M'Coy, 5. Nebulipora papillata, M'Coy, 5. Nomenclature of Monticuliporoids proposed by Dybowski, 16-18. 240 INDEX. Orbipora, Eichw., 1, 10, 11, 20, 24. Orbipora arborescens, Dyb., 24. Orbipora distincta, Eichw., 10, 24. Orbipora fungiformis, Eichw., 10, 24. Orbipora Panderi, Dyb., 24. Orbitidites, Eichw., i, 2. ■* Peronopora, Nich., 100, 103, 215. * Peronopora Cincinnatiensis, James, 226. * Peronopora frondosa, D'Orb., 216. * Peronopora molesta, Nich., 224. * Peronopora (?) Ortoni, Nich., 228. Porenkaniilchen, 18, 46. * Prasopora, Nich. and Eth. jun., 100, 103, 202. * Prasopora Grays, Nich. and Eth. jun., 203. * Prasopora Newberryi, Nich., 212. * Prasopora Selwynii, Nich., 206; var. hospitalis, Nich., 209. Piilodictya pavo7iia, D'Orb., 195. Solenopora, Dyb., 19, 22. Solenopora spongioides, Dyb., 22. Spiniform corallites of Monticulipora, 18, 45 ; of Stenopora, Lonsd., 48. Stdlipora, Hall, 20, 23. Stellipora constellata, Dyb., 23. Stellipora Revalensis, Dyb., 23. Stenopora, Lonsd., 6, 16, 81-84. Stenopora, M'Coy, i, 7. Stenopora adherens, Bill., 10. Stenopora columnaris, Schloth., 5. Stenopora columnaris, Dyb., 18. Stenopora crassa, Lonsd., 4. Stenopora crinita, Lonsd., 24. Stenopora exilis, Dawson, 14. Stenopora fibrosa, Goldf. (M'Coy), 7. Stenopora granulosa, Phill. (M'Coy), 7- * Stenopora Howsii, Nich., 82, S3. Stenopora inflata, De Kon. (M'Coy), 7. Stenopora Jackii, Nich. and Eth. jun., 81,83. Stenopora patula, Bill., 10. Stenopora spinigera, Lonsd., 4. Stenopora tumida, Phill. (M'Coy), 7. Stenopora tumida, M'Coy, 120. Tetradium, Safford, 85. Trachypora, E. and H. (Dyb.), 19, 23. Trachypora porosa, Dyb., 23. * Trematopora, Hall (Dyb.), 20, 26, 102, Wandrohrchen, 18, 46. Wandstrange, 18, 48. PKINTRD BY WIM.IAM BLACKWOOD AND SONS. PLATE I. Fig. I. Fragment of the corallum of Monticulipora {^Heterotrypa) moniliformis, Nich., from the Hamilton Formation (Devonian) of Arkona, Ontario, of the natural size. The specimen shows more conspicuous " monticules " than is usually the case in this species. Fig. I a. Portion of the surface of the same, enlarged eighteen times, showing the blunt tubercles or spines (spiniform corallites) between the calices. Fig. I b. Portion of a tangential section of the same, enlarged eighteen times, showing the normal corallites, with an occasional small corallite at their angles of junction, and the numerous thick walled hollow spines (spiniform corallites). Fig. I c. Part of a vertical section of the same, enlarged eighteen times, show- ing the numerous tabulae, and the thickening of the walls of the corallites as they approach the surface. Fig. 2. Fragment of the corallum of Monticulipora (^Heterotrypd) Barraiidi, Nich., from the Hamilton Group (Devonian) of Arkona, Ontario, of the natural size. Fig. 2 a. Portion of the surface of the same, enlarged eighteen times. Fig. 2 /'. Tangential section of the same, enlarged eighteen times, showing the thick-walled corallites and the occasional development of spiniform tubes. Fig. 2 c. Part of the same section, enlarged fifty times. Fig. 2 d. Vertical section of the same, enlarged eighteen times. Fig. 3. A specimen of Monticulipora {Monotrypa) calceola, Miller and Dyer, from the Cincinnati group of Ohio, of the natural size. Fig. 3 a. A smaller example of the same, of the natural size. Fig. 3 b. Part of the surface of the same, enlarged eighteen times. Fig. 3 c. Tangential section of the same, enlarged eighteen times. Fig. 3 d. Part of the preceding section, enlarged fifty times, showing the peculiar small tubes at the angles of junction of the corallites. Fig. 3 e. Vertical section of the same, embracing the entire thickness of the corallum, enlarged eighteen times. Fig. 4. A fragment of Monticulipora {Heterotrypa) Jtodulosa, Nich., of the natural size, from the Cincinnati group of Ohio. Fig. 4 a. Part of the surface of the same, enlarged eighteen times. Fig. 4 b. Tangential section of the same, enlarged eighteen times. Fig. 4 c. Part of a transverse section of the same, including the narrow peri- pheral zone, and the greater part of the axis, enlarged eighteen times. Fig. 4 d. Part of a vertical section, enlarged eighteen times. H.Alleyne Nicholson del. Plate r ;;V'^W^C ^'^ 4.6 r, y^rv^r^ ^-.d. CBerjeau, lith Walerston k Sons Lith'* Edin.'' PLATE II. Kig. I. A specimen of Monticulipora {Htieroirypa) gracilis, James, from the Cin- cinnati group of Ohio, of the natural size. Fig. I a. Surface of the same, enlarged eighteen times. Fig. I b. Small portion of the surface of the same, enlarged fifty times. Fig. 2. A specimen oi Monticulipora {Hctcrotrypa) ramosa, D'Orb., of the natural size. From the Cincinnati group of Ohio. Fig. 2 a. Surface of the same, enlarged eighteen times. Fig. 3. A specimen of Monticulipora rugosa, Edw. and Haime, of the natural size. From the Cincinnati group of Ohio. Fig. 4. A specimen of Monticulipora Dalii, Edw. and Haime, of the natural size. From the Cincinnati group of Ohio. Fig. 5. A specimen of Monticulipora {Afonotrypa) briarea, Nich., of the natural size. From the Cincinnati group of Ohio. Fig. 5 a. Tangential section of the same, enlarged eighteen times. Fig. 5 b. Fart of the preceding section, enlarged fifty times. Fig. 5 c. Vertical section of the same, enlarged eighteen times. I'^ig. 6. Fragment of the crust of Monticulipora {Feronopora) Cincinnatiensis, James, of the natural size, showing the prominent monticules. From the Cincinnati group of Ohio. Fig. 6 a. Part of the surface of the same, enlarged eighteen times. Fig. 6 b. Part of a tangential section of the same, enlarged eighteen times, showing the large tubes with their incomplete tabulae and the intercalated small tubes. Fig. 6 c. Vertical section of the same, enlarged eighteen times, showing the incomplete tabula; of the large tubes. Fig. 7. A specimen of Monticulipora {Hctcrotrypa) implicata, Ulrich, of the natural size. From the Cincinnati group of Ohio. Fig. 7 a. Fractured extremity of the same specimen, enlarged three times, showing the arrangement of the tubes. Fig. 7 b. Portion of the surface of the same, enlarged eighteen times. Fig. 7 c. A small part of the surface of the same, enlarged fifty times, showing the prominent blunt spines (spiniform corallites) between the large tubes. Fig. 7 d. Tangential section of the same, enlarged eighteen times. Fig. 7 c. Part of a vertical section of the same, enlarged eighteen times. H. Alleyne Nicholson del. Plate II, C.Bfirjeau, lith "Waterston k Sons. Lift" Edii PLATE III. Fig. I. A fragment of Mouticulipora {Heterotrypa) tiimida, Phill., from the Car- boniferous rocks of Redesdale, Northumberland, of the natural size. Fig. I a. Part of the surface of the same, enlarged eighteen times. Fig. I b. Another part of the same specimen, showing a group of small coral- lites, similarly enlarged. Fig. I c. A calice of the same, enlarged fifty times, showing the blunt spines round the margin. Fig. I d. Tangential section of the same, enlarged eighteen times, showing the thick walls of the corallites, and the numerous hollow spines (spiniform corallites). Fig. I e. Vertical section of the same, enlarged eighteen times. Fig I f. Vertical section of a single corallite of the same, close to its mouth, enlarged fifty times, showing the peculiar structure of the wall. In the wall on the right-hand side is seen one of the hollow spines. Fig. 2. Fragment of Mouticulipora tumida, Phill., var. miliaria, Nich., from the Carboniferous rocks of Redesdale, Northumberland, of the natural size. Fig. 2 a. Part of the surface of the same, enlarged eighteen times, showing the numerous interstitial tubes. Fig. 2 b. Part of a tangential section of the same, enlarged eighteen times. Fig. 2 c. Part of the preceding section, enlarged fifty times. Fig. 3. A specimen of Mouticulipora {Hcterotrypa) O'Nealli, James, from the Cincinnati group of Ohio, of the natural size. Fig. 3 a. Part of the surface of the same, where the calices are open, enlarged fifteen times. Fig. 3 b. Part of the surface of another specimen where the larger calices are closed by opercula, enlarged fifteen times. Fig. 3 c. Part of a tangential section of the same, enlarged eighteen times, showing the large and small corallites. Fig. 3 d. Small portion of the preceding section, enlarged fifty times, showing the structure of the wall. Fig. 3 e. Part of the axial region of a transverse section of the same, enlarged eighteen times, showing the thin walls and angular form of the corallites. Fig. 3/ Part of a vertical section of the same, enlarged eighteen times. Fig. 4. Fragment of the shell of Strophonieua alteruata, Conrad, with a small colony o{ Mouticulipora [Ferotiopora) (?) Ortoni, Nich., growing upon it, of the natural size. From the Cincinnati group of Ohio. Fig. 4 a. Portion of the surface of the same, enlarged fifty times, showing the peculiar form of the calices, and the rounded tubercles surrounding them. Fig. 4 /'. Part of a tangential section of the same, enlarged sixty times, showing the peculiar shape of the corallites and their incomplete tabula, together with the numerous hollow spines (spiniform corallites). Fig. 4 c. Vertical section of the same, embracing the entire thickness of the colony, enlarged eighteen times. Fig. 4 d. Part of an oblique tangential section, cutting the tubes longitudinally. enlarged eighteen times. H.Alle3me Nicholson, del Plate 111. ■%^ _. R ^^^^-^i in O A K ^^ 0 C.Berreau. lith Walerstoii ?,.- Sons,Lith'''Eain PLATE IV. Fig. I. A specimen of Moiiticulipora {Prasopora) Newberry i, Nich., from the Cincinnati group of Ohio, viewed from above, of the natural size. The thin corallum is fractured in various directions. Fig. I a. View of the margin of the same, of the natural size, showing the thickness of the corallum. Fig. I b. Part of the surface of the same, enlarged eighteen times. Fig. I c. Tangential section of the same, enlarged eighteen times, showing the two kinds of corallites, and the incomplete tabulse of the large tubes. Fig. I d. Part of the preceding section, enlarged fifty times. Fig. I e. Vertical section, enlarged eighteen times, embracing the entire thick- ness of the corallum, and showing the different tabulation of the larger and smaller corallites. Fig. 2. Outline of a portion of an Orthoceras covered by a colony oi Monticuli- pora {Monotrypa) tuberciilata, Edw. and Haime (= M. corticans, Nich.), of the natural size, showing the form of the elongated tubercles. From the Cincinnati group of Ohio. Fig. 2 a. Part of the surface of the same, enlarged eighteen times. Fig. 2 b. Part of a tangential section of the same, enlarged eighteen times. Fig. 2 c. Small portion of the preceding section, enlarged fifty times, showing the structure of the wall. Fig. 3. A specimen of MoJiticidipora {Monotrypd) discoidea, James, viewed from above, of the natural size. From the Cincinnati group of Ohio. Fig. 3 a. Under side of the same specimen, showing the basal epitheca. Fig. 3 b. Side-view of the same, showing the thickness of the corallum. Fig. 3 c. Tangential section of the same, enlarged eighteen times, showing the hollow spines (spiniform corallites) at the angles of the ordinary tubes. Fig. 3 d. Part of the preceding section, enlarged fifty times. Fig. 3 e. Part of a vertical section, of the natural size, embracing the whole thickness of the corallum. Fig. 3 / A single tube from the preceding section, enlarged fifty times, showing the structure of the wall. Fig. 4. A specimen of Monticidipora {Diplotiypd) calycula, James, of the natural size, from the Cincinnati group of Ohio. The surface bearing the calices • is buried in the matrix, and all that is seen is the deeply concave basal epitheca. Fig. 4 a. Tangential section of the same, enlarged eighteen times. Fig. 4 b. Vertical section of the same, embracing the whole thickness of the corallum, enlarged eighteen times. H.Alleyne Nicholson, del. Plate IV. jdJkMU 2^ C. Berjeau, liih. Waterstoii2^ Sons. Litl"E3m PLATE V. Fig. 1. A specimen of Monticulipora {Hdcrotrypa) Audrcivsii, Nich., from the Cincinnati group of Ohio, of the natural size. Fig. I a. Part of the surface of the same, embracing one of the clusters of large tubes, enlarged twenty-five times. Fig. 2. A specimen oi Monticulipora {Heterotrypa) siibpidchella, Nich., from the Cincinnati group of Ohio, of the natural size. Fig. 2 a. Part of the surface of the same, including one of the clusters of small tubes, enlarged twenty-five times. Fig. 3. Outline of a specimen oi Monticulipora {Heterotrypa) Daivsoni, Nich., of the natural size. From the Cincinnati group of Ohio. Fig. 3 a. Part of the surface of the same, of the natural size, showing the prominent elongated tubercles. Fig. 3 h. Part of the surface of the same, enlarged eighteen times. Fig. 3 c Tangential section of the same, enlarged eighteen times. Fig. 3 d. Part of the preceding section, enlarged fifty times. Y\g. 3 e. Vertical section of the same, embracing the whole thickness of the corallum, enlarged eight times. Fig. 3/ Part of the outer margin of the preceding section, enlarged eighteen times. Fig. 4. A thin variety of Monticulipora {Peronopora) fronJosa, D'Orlx, from the Cincinnati group of Ohio, of the natural size. Fig. 4 a. Tangential section of the same, enlarged fifty times, showing the imperfect tabular of the larger corallites, the intercalated small corallites, and the moderate development of " spiniform corallites." Fig. 5. A fragment of Monticulipora {Peronopora) frondosa, D'Orb., from the Cincinnati group of Ohio, of the natural size, showing the faintly marked monticules. Fig. 5 a. Broken edge of the same specimen, of the natural size, showing the general arrangement of tlie corallites. H Alleyne Nicholson, del. Plate V. C.BerTeau, litL, Watepstou fc Sons.LHlf ^Eimf PLATE VI. Fig. I. ()utline of a specimen oi Monticitlipiva {Hctcrotrypa) i)ia)iuiiulafa, D'Orb., from the Cincimiati group of Ohio, of the natural size. Fig. I a. Portion of the surface of a specimen of the same, showing very faintl) marked monticules, of the natural size. Fig. I b. Portion of the surface of another specimen of the same, showing more conspicuous tubercles, of the natural size. Fig. I I. Surface of the same, enlarged eighteen times. Fig. I d. Tangential section of the same, taken just below the surface, showing the larger and smaller tubes, and the occasional hollow spines, (spiniform corallites). Fig. 1 c. Part of the same section, enlarged fifty times. Fig. \ f. Another tangential section, taken at a deeper le\'el than the preceding, enlarged twenty times. Fig. I g. Portion of a vertical section of the same at right angles to its flat sur faces, enlarged eighteen times, showing the different tabulation of the larger and smaller tubes. Fig. 2. A specimen oi Mo7itlcuUpora {Peronopora) molesta, Nich., from the Cincin- nati group of Ohio, of the natural size, showing the well-marked mt)nticules. Fig. 2 a. Part of the surface of the same, enlarged eighteen times. Fig. 2 b. Tangential section of the same, enlarged eighteen times, showing the large and small corallites, and imperfect tabulae of the former. Fig. 2 c. Part of the preceding section, enlarged fifty times. Fig. 2 d. Part of a vertical section of the same, showing the close tabulation of tlie small corallites, and the incomj)lete tabula of most of the large tubes. Fig 3. A specimen oi MonticuUpoi-a {Moiiotrypd) pavouia, D'Orb. ( = M. dafhra- tula, James), from the Cincinnati group of Ohio, of the natural size. F'ig. 3 a. Portion of the surface of the same, enlarged eighteen times. H.AUeyne Nicholson, del Plate VI. CBerjeau, JiLh., Waterston?c Sons.Lit}?- Edm- ^^.