/ Ko ^ t\o* A Guide to the Common Diatoms at Water Pollution Surveillance System Stations June 1966 U.S. DEPARTMENT OF THE INTERIOR Federal Water Pollution Control Administration ru ru A Guide to the Common Diatoms at Water Pollution Surveillance System Stations UNITED STATES DEPARTMENT OF THE INTERIOR Federal Water Pollution Control Administration Water Pollution Surveillance 101U Broadway, Cincinnati, Ohio ^5202 June 1966 11 Preface Plankton studies were initiated, in 1957 under the direction of Dr. Clarence M. Tai z veil and Dr. C. Mervin Palmer. The studies which they initiated were a part of the Public Health Service program to collect basic data on the quality of water in major waterways . In the beginning plankton studies were limited to Sedgwick-Rafter counts of phytoplankton and zooplankton. As the phytoplankton populations at the various stations were characterized, the dominat role of the diatoms became apparent, and preparations were begun for more intensive work with these forms. After the early species identifications were made through consultations or correspondence with Dr. Matthew Hohn, Dr. Charles Reimer, Dr. Friedrich Hustedt, and Dr. G. D. Hanna, routine diatom species identification and enumeration were inaugurated in 1959 by Dr. Louis G. Williams, who was in charge of plankton studies from September 1958 to December 1962. Di- Cornelius I. Weber assumed responsibility for the plankton studies in September 19&3- Mr. Louis Grivetti who was on the staff of the plankton laboratory from 1962-196^ developed the first draft of this guide to consolidate information which would be helpful to beginners in diatom identification work. The present form of this guide is the result of extensive additions and revisions by Dr. Weber and his staff. The diatom studies have become a vital part of the plankton program. The specificity of the diatom data has rendered it especially useful in characterizing water quality. Joseph B. Anderson In Charge, Aquatic Biology iii CONTENTS Page 1 . Introduction 1 2. Collection and preparation of diatom material... 3 3. The diatom cell wall h k. Glossary 6 5 . Generic key 9 6. Alphabetical list of genera 16 7. Illustrated species 17 8. Figure credits 18 9. Station map 99 10. Diatom distribution charts 100 Introduction A comprehensive treatise on the diatoms of the United States is yet to he published. Existing references dealing with the algae of this country are either very provincial or shallow in their coverage of the diatoms, therefore a large number of domestic and foreign publi- cations must be consulted to find descriptions of all of our conmon species. This is a formidable task for the beginning diatom student. Descriptions of the diatom species which are most frequently encountered at WPSS stations have been assembled in this illustrated guide which was prepared to serve as a bench reference for biologists in our laboratory who are being trained in diatom identification. The guide also contains a glossary and generic key. The key was constructed with the beginner in mind, and is based entirely on the shape and markings of the diatom cell wall as observed in material mounted in hyrax. No attempt was made to place the taxa in their proper phylogenetic order. Laboratory personnel are encouraged to consult the taxonomic references for species identification. We are indebted to Dr. Charles Reimer, Dr. Eugene Stoermer, and Dr. Matthew Hohn for carefully reviewing the manuscript and making many helpful suggestions. We are also grateful to the various authors and publishers who have granted permission to use selected figures from their publications. -2- Staff biologists who have been engaged in diatom work and have contributed to the preparation of this manual include, Carol Scott, Julia Maloney, Albert Katko, Mary Jo Sage, Louis Grivetti, Ronald Raschke, Mason Fenwick, Lydia Corrill, and Gretchen Oswald. Cornelius I. Weber, Ph.D. In Charge, Plankton Studies Collection and Preparation of Diatom Material The Water Pollution Surveillance System plankton samples used for diatom analyses are obtained from water plant intakes or directly from rivers or lakes at one hundred and thirty stations across the United States. The algae in the samples are concentrated by centrifuging twenty minutes at 1000 x G. Several drops of plankton concentrate are placed on a #1 coverglass, the coverglass is dried cautiously to avoid splattering, and incinerated thirty minutes on a hot plate at 1000 F. This treatment drives off most of the organic matter present, leaving only the siliceous diatom cell walls (thin-walled forms such as Rhizosolenia eriensis and Melosira crenulata may be difficult to observe). A drop of Hyrax mounting medium is placed in the center of a 75 nan x 25 mm glass slide heated to approximately 200 F. When the solvent has evapor- ated (the solvent-free Hyrax is hard and brittle at room temperature), the coverglass bearing the incinerated diatoms is inverted and placed on the drop of Hyrax, the slide is removed from the heat, and pressure is applied to the coverglass until the Hyrax cools and hardens (10 - 15 sec). The finished slide is examined at 970X. THE DIATOM CELL WALL The diatom cell wall (frustule) is made of silica and consists of two overlapping halves, each composed of a more or less flat surface, the valve, to which are joined one or more hoop-like bands, the girdle and intercalary bands (see below). r -\ LI ^ / > j vm ib gb Girdle view of frustule showing valves, v; intercalary bands, ib; girdle band, gb; girdle, g; and valve mantle, vm. The valves of the centric diatoms are generally circular in outline, with their markings arranged symmetrically about a central point; whereas, the valves of the pennate diatoms are generally elongate (linear) with their markings arranged in transverse rows along each margin. Pennate Centric Valve views of pennate and centric diatoms showing the central area, a; raphe, r which usually occupies the medial axis of the valve; striae, s; and costae, c. Planes and axes of symmetry are employed in keying out some of the pennate genera. They are shown in the figures below. Oblique view of a pennate frustule showing planes; apical plane (along longitudinal or medial axis), a; transapical plane (along the transverse axis), t. Oblique view of a pennate frustule showing axes : apical axis , a; transapical axis, t; and the pervalvar axis, p. 6 GLOSSARY Arcuate - bent like a bow (see Fragilaria arcus , p. 38) Brackish - having a dissolved salt content intermediate between fresh and salt water. Capitate - swollen at one or both ends in valve view (see Caloneis amphisbaena, p. 63) Carinal dots - circular or oval pores more or less evenly spaced along the keel, usually appearing as dots or lines (see Nitzschia, p. 90) Costae - internal or external linear thickenings of the valve surface appearing as ribs; because of light diffraction, the tapered shoulders of the costae may appear as dark lines (see Cyclotella Meneghiniana, p. 26) Facet - (alveola) a circular or hexagonal thin area in the valve sur- face, surrounded by a ridge which may extend internally or extern- ally from the valve surface (see Coscinodiscus, p. 31) Frustule - the siliceous diatom cell wall consisting of two separate halves. Fusiform - broadest at the middle and tapering at each end, spindle- shaped (naviculoid). Girdle - region of the frustule between the two valves. Girdle-bands - the two overlapping hoop-like bands which join the two halves of the frustule. They may be connected directly to the valve margins or the intercalary bands. Girdle view - side view of the frustule. Intercalary bands - hoop-like bands located between the girdle-band and the valve (see Rhizosolenia, p. 22) Keel - a ridge projecting from the valve -surface, enclosing the "canal" raphe, usually not medial on the valve (see Nitzschia, p. 89) Linear - long and nearly uniform in width. Micron - 0.001 millimeter. Multiseriate - having more than one row of punctae (see Stephanodiscus astrea, p. 28) Nodule - internal thickening of the cell wall in the central area or terminal portions (poles) of the valves of pennate diatoms. Ocellus - a raised, rounded or ovate thickening of the valve surface having the appearance of a large pore (see Cyclotella ocellata, P- 27) Poles - extreme ends of the valves of pennate diatoms. Pseudoraphe - a smooth, linear space between the medial ends of the striae or costae on the valves of pennate diatoms. A term applied only to valves without a true raphe (see Synedra ulna, p. k-5) Punctae - small holes (pores) or thin, circular, sieve-like areas in the frustule . Raphe - a fissure or slit in the valve face which may be along or eccentric to the medial axis of the valve; when located in a keel or wing it is referred to as a "canal" raphe. Rhomboid - a parallelogram in which the angles are oblique and the adjacent sides are unequal (see Nitzschia, p. 89) Septae - internal partitions or cross walls, usually appearing as dark lines (see Tabellaria fenestra ta, p. 32) Shadow-lines - dark "diffraction" lines which appear in the frustule wherever abrupt changes in thickness of the valve face occur (see Caloneis, p. 63) 8 Sigmoid - s-shaped (see Gyros igma, p. 67) Stellate - star-shaped, radiating from a point. Striae - linear markings on the frustule which are due to closely placed punctae, or to hollow chambers in the cell wall (may sometimes appear as costae). Sulcus - annular groove between the valve mantle and girdle (see Melos ira ambigua, p. 19) Uniseriate - having one row of punctae (see Coscinodiscus, p. 31 ) Valve - the face of the diatom frustule. Valve mantle - the part of the valve which extends below the shoulder. In the Melos iras the valve mantle is a cylindrical surface that may be 30u long (see Melos ira granulata, p. 20) Wing - a thin projection of the valve surface, more highly developed than a keel; generally arising near the margin of the valve, but some- times arising near the medial axis. May enclose the "canal" raphe (see Surirella, p. 87) 9 GENERIC KEY la Valves with true raphe or pseudoraphe; ornamentation transverse and/ or longitudinal 8 lb Valves without true raphe or pseudoraphe; ornamentation radial about a central point 2 2a Frustules usually united into long filaments Melosira (p. 19) 2b Frustules not usually united into long filaments; usually solitary but may form short chains 3 3a Frustules with intercalary bands; usually seen in girdle view; one or two long spines arising from each valve.... k 3b Frustules without intercalary bands 5 ka. One long spine arising from each valve Rhizosolenia (p. 22) kh Two long spines arising from each valve. . . .Attheya (p. 23) 5a Valves with two marginal protuberances or horns on opposite sides of the valve; usually seen in girdle view. Biddulphia (p. 23) 5b Valves lacking protuberances 6a Valve margin with costae; ornamentation in central area different from margin Cyclotella (p. 2k ) 6b Valve margin otherwise; central area not sharply distinct from margin; valves with radial rows of punctae or with geometric facets 10 7a Punctae in multiseriate rows near valve margin, each row gradually or abruptly becoming uniseriate toward the center; marginal spines always present Stephanodiscus (p. 28) 7b Punctae in uniseriate rows throughout, or with geometric facets Coscinodiscus (p. 31 ) 8a True raphe present on at least one valve; raphe may be very short or rudimentary, or may be concealed in a keel or wing 15 8b True raphe absent, pseudoraphe present on both valves... 9 9a Frustules with thick longitudinal septae running parallel to the valve faces Tabellaria (p. 32) 9b Frustules without septae 10 10a Valves with thickened internal transverse ribs (costae), most of which extend completely across the valve face... 11 10b Valves without thickened internal transverse ribs. 12 11a Valves symmetrical about the transapical plane Diatoma (p. 33) lib Valves asymmetrical about the transapical plane Meridion (p. 36) 12a Frustules with bulbous ends, slightly concave in girdle view, typically forming stellate colonies Asterionella (p. 37) 12b Frustules without bulbous ends, typically not forming stellate colonies 13 11 13a Valves symmetrical about the transapical plane lk 13"b Valves asymmetrical about transapical plane Opephora (p. 38) l4a Frustules typically forming long ribbon-like chains, rarely solitary Fragilaria (p. 38 ) l^b Frustules typically solitary, sometimes forming stellate colonies; striae often appearing as costae Synedra (p. k2) 15a Raphe evident on at lease one valve l6 15b Raphe not evident, concealed in a keel or wing 35 l6a Valves similarly ornamented, raphe on both valves 19 l6b Valves not similarly ornamented, raphe on one valve, opposing valve with pseudoraphe, or with rudimentary raphe near valve poles 17 17a Valves elliptical, never linear, sometimes bent along the apical axis Cocconeis (p. hj) 17b Valves not elliptical, usually linear, and usually bent along the transapical axis 18 l8a Valves symmetrical about the transapical plane, one valve with completely developed raphe, opposing valve with pseudoraphe Achnanthes (p. 50) l8b Valves asymmetrical about the transapical plane, one valve with completely developed raphe, opposing valve with rudimentary raphe near valve poles Rhoicosphenia (p. 52) 12 19a Raphe rudimentary, short, near poles only Eunotia (p. 53) 19b Raphe fully developed, extending the length of the valves 20 20a Valves symmetrical about both the transapical and apical plane 2k 20b Valves asymmetrical about either the apical or transapical plane 21 21a Valves symmetrical about the transapical plane, asymmetrical about the apical plane 23 21b Valves asymmetrical about the transapical plane, symmetrical about the apical plane 22 22a Valve margins with longitudinal "shadow"-lines , Gomphoneis (p. 5I4.) 22b Valve margins lacking longitudinal shadow"-lines Gomphonema (p. 5^-) 23a Valve faces parallel Cymbella (p. 57) 23b Valve faces not parallel, both valves faces can be seen in girdle view Amphora (p. 60) 2^a Valves with elongate central or terminal nodules 25 24b Valves without elongate central or terminal nodules 26 25a Central nodule drawn out to at least half the length of the valve Amphipleura (p. 62 ) 25b Central nodule drawn out less than half the length of the valve Frustulia (p. 62 ) 13 26a Valves with longitudinal "shadow"-lines or blank spaces 27 26b Valves without longitudinal lines or blank spaces 29 27a Transverse striae continuous, crossed by one or two longitudinal "shadow "-lines paralleling valve margin.... Caloneis (p. 63) 27b Transverse striae discontinuous, interrupted by blank spaces or "shadow"-lines 28 28a Longitudinal "shadow "-lines or blank spaces near valve margins; ends of raphe near central nodule usually turned in opposite directions Neidium (p. 6^) 28b Longitudinal "shadow"-lines or blank spaces scattered, central pores of raphe near central nodule turned if at all in the same direction Anomoeoneis (p. 65) 29a Valves and raphe s igmoid 30 29b Valves and raphe not sigmoid 31 30a Valves with transverse and longitudinal striae Gyros igma (p. 67) 30b Valves with transverse and oblique striae Pleurosigma (p. 67) 31a Frustules with septae Mastogloia (p. 68) 31b Frustules without septae 32 32a Raphe enclosed in a siliceous rib Diploneis (p. 68) 32b Raphe not enclosed in a siliceous rib 33 33a Valves with chambered striae appearing as heavy costae; valves usually with parallel sides and broadly rounded poles. Pinnularia (p. 70) 33b Valves with striae appearing otherwise 3^ 1^ 3^a Central area extending laterally to the margins of the valve, striae absent along lateral margins of the central area Stauroneis (p. 70) 3*)-b Central area not extending to the margins of the valve, striae present along lateral margins of the central area Navicula (p. 71) 35a Keel elevated into a lateral "wing" or flattened on the valve surf ace 37 35b Keel elevated into an axial "wing" extending along the central axis of the valve 36 36a Keel sigmoid, usually seen in girdle view (hour-glass- shaped), frustule twisted along the longitudinal axis; girdle broad with many longitudinal folds Amphiprora (p. 80) 36b Keel not sigmoid, girdle simple, not folded, keel eccentric Tropidoneis (p. 82) 37& Valves with numerous internal transverse ribs extending completely across the valve 38 37b Valves without internal transverse ribs h-0 38a Raphe and axial area with "V"-shaped medial extension; with transverse septae appearing as costae and alternat- ing with two or more rows of punctae Epithemia (p. 83) 38b Raphe and axial area without a "V"-shaped medial extens ion 39 15 39a Raphe canal with pores, valves symmetrical to longitudinal axis Denticula (p. 8*4-) 39h Raphe canal without pores, valves asymmetrical to the longitudinal axis Rhopalodia (p. 8^ ) 40a Valves with lateral keel extending along both margins of each valve Vl kOb Valves with lateral keel extending along one margin of each valve h-2 ^la Valve face longitudinally undulate, undulations conspicuous in girdle view; with broad, short, peripheral costae; longitudinal pseudoraphe present Cymatopleura (p. 86) 4lb Valve face not longitudinally undulate; valve face with longitudinal folds which appear as heavy costae, folds not conspicuous in girdle view; girdle view rectangular, naviculoid, wedge shaped or sigmoid; valve view linear, elliptical, ovate or spirally twisted Surirella (p. 87) h2a Keels eccentric to the median axis, diagonally opposite; frustules rhombic in cross section, transversely striate, punctate or lacking ornamentation; a row of circular pores ("carinal dots") developed within the keel; frustules usually solitary but occasionally forming irregular ribbon- like chains or stellate colonies Nitzschia (p. 89) ^2b Keels eccentric to the median axis, directly opposite; frustules rectangular in cross section, transversely striate or punctate, capitate ends, medianly constructed. . .Hantzschia (p. 98) 16 Alphabetical list of Genera Genus Page Achnantb.es Amphipleura Amphiprora Amphora Anomoeoneis Asterionella Attheya Biddulphia Caloneis Cocconeis Coscinodiscus Cyclotella Cymatopleura Cymbella Denticula Diatoma Diploneis Epithemia Eunotia Fragilaria Frustulia Genus Page 50 Gomphoneis 54 62 Gomphonema 54 80 Gyros igma 67 60 Hantzschia 98 65 Mastogloia 68 37 Melosira 19 23 Meridion 36 23 Navicula 71 63 Neidium 64 47 Nitzschia 89 31 Opephora 38 24 Pinnularia 70 86 Pleurosigma 67 57 Rhizosolenia 22 84 Rhoicosphenia 52 33 Rhopalodia 84 68 Stauroneis 70 83 Stephanodiscus 28 53 Surirella 87 38 Synedra 42 62 Tabellaria 32 Tropidoneis 82 17 Illustrated Species A total of lo^t- species are illustrated, representing **3 of the common genera found at the Water Pollution Surveillance System stations. Some of the species were selected primarily to demonstrate the morphological diversity within the genera. The figures have been selected from a number of publications (p. 18) and the figure credits are referred to by number immediately following the species names. The cell dimensions given are generally those from the figure source, but in some cases these have been supplemented with our own observations. The geographical distribution of 96 of the species is shown in the accompanying chart (p. 100), taken from "Plankton Population Dynamics", by L. G. Williams, PK3 Pub. No. 663, Suppl. 2, 1962. Additional information regarding diatom distribution can be found in the WP3S Annual Compilations of Data, 1960-61, 1961-62, and 1962-63, PHS Pub. No. 663. 18 FIGURE CREDITS 1. Boyer, Charles S., 1916. The Diatomaceae of Philadelphia and Vicinity. J. B. Lippincott Co., Philadelphia. 2. Hohn, Matthew H. , and Joan Hellerman, 1963. The Taxonomy and Structure of Diatom Populations From Three Eastern North American Rivers Using Three Sampling Methods. Transactions of the American Microscopical Society. 82(3) :250-329. 3. Huber-Pestalozzi, G., and F. Hustedt, 19^2. Die Kieselalgen. In: A.Thienemann, Das Phytoplankton des Susswassers, Die Binnengewasser, Band XVI, Teil II, Halfte II. E. Schweizerbart 'sche Verlagsbuch- handlung, Stuttgart. k. Hustedt, F., 1930. Die Kieselalgen. In: L. Rabenhorst, Kryptogamen- Flora von Deutschland, Osterreich, und der Schweiz, Band VII. Akademische Verlagsgesellschaft m.b.H. , Leipzig. 11 5. Hustedt, F., 1930. Bacillariophyta. In: A. Pascher, Die Susswasser- Flora Mitteleuropas , Heft 10; Gustav Fischer, Jena. 11 6. Hustedt, F., 19^9« Susswasser-Diatomeen. Imprimerie M. Hayez, Bruxelles . 7. Plankton Laboratory staff, WPSS. 8. Patrick, R., 1959- The Bacillariophyceae. In: W. T. Edmondson, Fresh-water Biology, H. B. Ward and G. C. Whipple, 2nd Edition, Wiley and Sons, N. Y. 9. Prowse, G. A., 1962. Diatoms of Malayan Freshwaters. Gardens1 Bulletin, Singapore. 19(l):l-104. 10. Smith, G., 1950. The Fresh-water Algae of the United States. 2nd Edition, McGraw-Hill Book Co., Inc., N. Y. 11. Tiffany, L. H. , and M. E. Britton, 1952. The Algae of Illinois. Univ. Chicago Press, Chicago. 12. van der Werff , A., and H. Huls, 1957-1961, 1963. Diatomeeenflora Van Nederland. Parts I, II, III, IV, V, VI. Stechert and Hafer, N. Y. 19 la Valves with true raphe or pseudoraphe; ornamentation transverse and/ or longitudinal 8 lb Valves without true raphe or pseudoraphe; ornamentation radial about a central point 2a Frustules usually united into long filaments - MELOSIRA Fig. 1. Melosira ambigua, (3), valves U-15u in diameter, 3-13M long; wide, angular sulcus. X 1000. Abundant in the Ohio and Mississippi Rivers. Notes : o cm valve view girdle view sulcus Fig. 2. Notes Melosira Binderana, (3), valves k- 25u in diameter, 3-7U long; in valve view may be confused with Stephanodiscus Hantzschii; has distinct pores on valve mantle ( shoulder ) . X 1000. Common in the Great Lakes. girdle view 1. Valve length in Melosira is measured from the valve face to the sulcus, along the pervalvar axis (half length). 2. This number refers to the figure source, 20 Fig. 3. Melosira distans, (3), valves 4-20u in diameter, 4-8p long. X 1000. Abundant in southeastern rivers, Notes girdle view var. lirata, form lacusris Fig. h. Melos ira granulata, (3), valves 5-21u in diameter, 5-l8|-i long; terminal cells usually with robust spines. X 1000. Common in northern U. S. -JTjnr :V;Y? srrvr. girdle view valve mantle Notes Fig. 5. Melosira herzogii, (7), valves 4u in diameter, 7m long. X 2000. Found most often in southeastern U.S. girdle view Notes : 21 Fig. 6. Melosira islandica, (3), valves 7-27U in diameter, 4-21u long; striae on valve mantle parallel to pervalvar axis. X 1000. Common in the Great Lakes and the Columbia River. nm Notes : girdle view, subsp. helvetica Fig. 7. Melosira italica, (3), valves 5-28u in diameter, 8-21u long; differentiated from M. ambigua by more robust spines and narrow sulcus. X 1000. Common in the Columbia River. valve view girdle view^ var. valida Notes : Fig. 8. Melosira varians , (3), valves 8-35(i in diameter, 9-13H long; no visible ornamentation. X 1000. Widely distri- buted. T JL valve view girdle view Notes 22 Notes on other species of MELQSIRA: 2b Frustules not usually united into long filaments; usually solitary but may form short chains 3a Frustules with intercalary bands; usually seen in girdle view; one or two long spines arising from each valve 3b Frustules without intercalary bands, One long spine arising from each valve - RHIZOSOLENIA Fig. 9. Rhizosolenia eriensis, (k) , cells 5-15u in diameter, 40-150u long; note the many intercalary bands in the girdle area. X 1000. Common in the Great Lakes. girdle view Notes : intercalary band 23 Fig. 10. Rhizosolenia minima, (k), cells h~ J\i in diameter, 15 -^Ou long (excluding spines). X 350. Southwestern U. S. (Red River). girdle view Notes : kb Two long spines arising from each valve - ATTHEYA Fig. 11. Attheya Zacharias i , (lQ ) , cells 12-40u in diameter; spines k0-6O\i long. X 500. In Ohio and Tennessee Rivers . girdle view Notes 5a Valves with two marginal protuberances or horns on opposite sides of the valve; usually seen in girdle view - BIDDULPHIA 2k Fig. 12. Biddulphia laevis , (10), cells 20-150n in diameter, 50-150H long; X 650. Southwestern U. S. is valve view girdle view Notes : 5b Valves lacking protuburances 6a Valve margin with costae; ornamentation in central area different from margin - CYCLOTELLA Fig. 13. Cyclotella atomus, (3), cells h-5i± in diameter; every 5th or 6th costae is thicker and darker than the others; single ocellus in central area. X 1500. Widely distributed. valve view Notes Fig. lk. Cyclotella antiqua, ( k) , cells 10-30(i in diameter; wedge-shaped depressions in central area. X 1200. In Great Lakes. valve view Notes : 25 Fig. 15. Cyclotella bodanica, (4), cells 20-80u in diameter; an isolated puncta occurs at the inner end of several shortened marginal costae. X 1000. In Great Lakes . Notes : Fig. 16. girdle view Cyclotella comta, (k) , cells 15-20u in diameter; similar to C. bodanica but lacking punctae at the end of shortened costae. X 1000. In Great Lakes. valve view valve view Notes : Fig. 17. Cyclotella glomerata, ( 3) , cells 4-10u in diameter; forming chains; often seen in girdle view. X 1000. In Great Lakes. Notes : 26 Fig. 18. Cyclotella Kutzingiana, (3), cells 10-20u in diameter; center ornamentation highly variable. X 1000. Common in Great Lakes. valve views Notes : Fig. 19. Cyclotella Meneghiniana, (12), cells 10-30u in diameter; heavy marginal costae give impression of scalloped border. X 1000. Widely distributed. valve view girdle view Notes : Fig. 20. Cyclotella michiganiana, (ll), cells 5-20u in diameter; valve margin with pronounced rim. X 1000. valve views Notes : 27 Fig. 21. Cyclotella ocellata, ( 3), cells 6-20u in diameter; central area with 3-^ ocelli. X 1000. In Great Lakes. valve views Notes Fig. 22. Cyclotella pseudostelligera, (7), cells 7-Su in diameter; has marginal spines. X 3000. Widely distributed. Notes : valve view Fig. 23. Cyclotella stelligera, (3), cells 5-25m in diameter. X 1000. Abun- dant in the southeast. Notes : valve view 28 Fig. 2k. Cyclotella striata, (U), cells 10-50u in diameter. Has a circular shadow line passing through the costae. X 1000. In Delaware and Hudson Rivers. valve view Notes Notes on other species of CYCLOTELLA 6b Valve margin otherwise; central area not sharply distinct from margin; valves with radial rows of punctae or with geometric facets 7a Punctae in multiseriate rows near valve margin, each row gradually or abruptly becoming uniseriate toward the center; marginal spines always present.- STEPHANODISCUS Fig. 25. Stephanodiscus astrea (3), cells 10-30u in diameter; spines not at end of each row of punctae. Outer punctae in double to quadruple rows, 12 punctae in lOu. X 1000. Widely distributed. valve view Notes 29 Fig. 26. Stephanodiscus dubius, (3), cells 10-25u in diameter. X 1000. In Great Lakes and Columbia River. valve view girdle view Notes Fig. 27. Stephanodiscus Hantzschii, (7), cells «-20u in diameter; 8-10 striae in 10^; striae very light; frustule often collapses during incineration; may be confused with Melosira Binderana. X 2000. Widely distributed. Notes : valve view Fig. 28. Stephanodis cus invisitatus, (7), cells 5-15U in diameter,* 15-20 striae in lOu; striae very light; easily confused with _S_« Hantzschii. X 2000. Ohio River Basin. valve view Notes : 30 Fig. 29. Stephanodiscus niagarae , (3), cells 30-100u in diamete r ; 3-5 rows of punctae in marginal region of striae, spines sub- marginal and more robust than in S_. astrea. X 900. Upper Mississippi and Missouri Rivers, Notes : valve view Fig. 30. Stephanodiscus tenuis , (3), cells 6-28u in diameter) spines at end of each row of striae. X 1000. Notes : valve view Notes on other species of STEPHANODISCUS. 31 7b Punctae in uni seriate rows throughout; or with geometric facets - COSCINODISCUS Fig. 31. Coscinodiscus denarius , (k), cells 40-90u in diameter. X 1000. Notes : facet valve view Fig. 32. Coscinodiscus lacustris , (k), cells 20-50u in diameter, with marginal spines. X 1000. Notes : valve view Fig. 33. Coscinodiscus Rothii, (8), cells 25-40|i in diameter. X 1000. In Red and Lower Mississippi Rivers. Notes : valve view 32 Other species of COSCINODISCUS. 8a True raphe present on at least one valve; raphe may be very short or rudimentary, or may be concealed in a keel or wing 8b True raphe absent, pseudoraphe present on both valves. 15 9 9a Frustules with thick longitudinal septae running parallel to the valve face - TABELLARIA. Fig. 3^- Tabellaria fene strata, (3), cells 30-l^Ou long, 3-9U wide; 18-20 striae in lOuJ^-S intercalary bands per cell. In Great Lakes and Columbia River. septum girdle view. X 1000 C= 0= =o Colony X 250 valve view. X 1000 Notes : 33 Fig. 35. Tabellaria flocculosa, (5), cells 12-50u long, 5-l6»i wide; about lb striae in 10u; many intercalary bands. X 1000. In Great Lakes and Columbia River. valve view girdle view Notes 9b Frustules without septae 10 10a Valves with thickened internal transverse ribs (costae), most of which extend completely across the valve face 11 10b Valves without thickened internal transverse ribs 12 11a Valves symmetrical about the apical plane - DIATOMA Fig. 36. Diatoma anceps, (5), cells 15-100u long, k-Q\i wide; internal costae narrow, 3-6 in 10n; striae delicate, 18-20 in 10|i. X 1000. In Colorado River. fipMLiliilllllTpJ rrwr valve view girdle view colony Notes: 34 Fig. 37. Diatoma elongatum. (5), cells 30-120u long, 2-k-\i wide; internal costae narrow, 6-10 in lOu; striae delicate, about l6 in lOu. X 1000. In Great Lakes and Columbia River. girdle view valve view of var. tenuis valve view Notes : Fig. 38. Diatoma hiemale , ( 4) , cells 15-100u long, 7 - 20u wide; internal costae robust, 2-4 in lOu; striae prominent, 18-20 in lOu. X 1000. girdle view of valve part of colony view girdle view of part of colony of var. mesodon valve view of var. mesodon Notes : 35 Fig. 39* Diatoma vulgare, (5), cells 30-60u long, 10-13|i wide; internal costae narrow, 6-8 in IOji; striae very delicate, about 18 in lOu. Widely distributed. Girdle view of part of colony X 500 valve view X 1000 valve view, var. brevis, X 1000 Notes : Notes on other species of DIATOMA. 3t> lib Valves asymmetrical about the transapical plane - MER3DI0N Fig. 4o. Meridion circulare, (12), cells 12-80u long, ^-8u vide; 3-5 internal costae In lOu; about 15 striae in lOu. X 1000. Widely distributed. valve view girdle view Notes: 37 12a Frustules with bulbous ends, slightly concave in girdle view, typically forming stellate colonies - ASTERIONET.T.A Fig. hi. Asterionella formosa, (3), cells 30-l^Ou long, l-2u wide; free ends inflated less than joined ends. Widely distributed. valve view X 1500 Colony X 500 Notes: Fig. h2. Asterionella gracillima, (3), cells 40-130U long, l-2u wide; similar to A. formosa except that the two poles of the cell are of equal size in both valve and girdle view. t"inimniiiiiiiln|"i""""t""""i"' ■lMlllllllllllll'lllini'lil|i|lllirili;"Un—^J valve view x 1500 Colony x 500 Notes: 38 12b Frustules without bulbous ends, typically not forming stellate colonies 13 13a Valves symmetrical about the transapical plane Ik 13b Valves asymmetrical about the transapical plane - OFEPHORA Fig. ^3. Opephora Martyi, (h) , cells 5-60u long, k~8\i wide; X 1000. valve view girdle views Notes : lk& Frustules typically forming ribbon-like chains, rarely solitary - FRAGILARIA Fig. hk. Fragilaria arcus, (5), cells 15-150u long, l)-7u wide; 15-18 striae in lOu; cells swollen on the concave side near the central area. X 1000. Abundant in the Delaware and Columbia Rivers. eOgggSSSSSSSS^^ valve views Notes: 39 Fig. 45. Fragilaria brevistriata, ( 5 ), cells 12-28u long, 3-5u vide; striae short, 13-17 in 10|i. valve view var. trigibba X 600 valve view var. inflata X 600 girdle view A V valve view X 1000 Notes : Fig. k6. Fragilaria capucina, ( 3 ), cells 25-100u long, 2-5u wide; striae delicate, about 15 in lOu; clear central area. X 1000. Abundant in northern waters. flrnmin'II.IL.illlllllinillllllU Illlll.lllllilllllllllllWnmmm, Vj^™ji" ' I'iiiii'i" iiniiiii'inii(iHiiiiii'iiini'l'"-J valve view valve view var. mesolepta girdle view Notes : ko Fig. 1*7. Fragilaria construens, ( 5 ), cells 7-25u long, 5-12u wide; striae delicate, 1^-17 in 10n; pseudorapne broader in central region. X 1000. Abundant in northern waters. valve view girdle view var . subsalina SVl'lV.S'.S-^-, .■■'^.'.WrVJ.'-V. girdle view ^TTTMIII'lllllllUIIIIUMIIIlllll Notes : valve view Fig. 1*8. Fragilaria crotonensis, (3,5), cells l*0-150n long, 2-3u wide; 15-18 striae in 10|X. X 1000. Widely distributed. Notes girdle view 11 ■ IHWIHUii.ii 1 u„. -—"""■" ■ m^mi valve view -pj^.j H 1 1 iff* Fig. 1*9. Fragilaria inflata, (12), cells l8-50u long, 6-10n wide, X 1200. In Great Lakes. — -^^^^ valve view girdle view Notes : hi Fig. 50. Fragilaria intermedia, ( 5 ), cells 15-60u long, 2-5n wide; 9-13 striae in lOu; central area clear on one side only. X 1000. ^nTrfflTTTm mmummii— umiuumiii Juiuiiiu:." ■■ cuiniiiun rnnimu II MJi ■ 1 1 . 1 1 r i n milium ii.iiui hi Hum ] iu hrrirminTiii 1 1 1 1 itt«^i nA (111)1111 1 It mm" valve view girdle view Notes: Fig. 51. Fragilaria leptostauron, (12), cells 13-30|i long, 10-l6u wide; striae coarse, 6-9 in lOu. X 1000. ' •A -;*•• rac *"T3 «?' n valve views girdle view Notes Fig. 52. Fragilaria pinnata, ( 5), cells 3-30u long, 2-6u wide; striae coarse 10-12 in lOu. X 1000. Widely distributed. valve view girdle view Notes : k2 l4b Frust\-J.es typically solitary, sometimes forming stellate colonies; ptriae often appearing as costae - SYNEDRA Fig. 53. Synedra actinastroides , (5), cells 35-&-U long, 2-k\x wide; striae snort, marginal, Ik in lOu. X 5&0. a-c, girdle views d, valve view Notes : F-''?. 5k. Synedra acus, ( 5 ), cells 100-300u long, 5-6u wide; striae 12-1*)- in lOu, finer than S. ulna. X 500. Widely distributed. valve view, var. angustissima '"'"mi .tr^"^rz~^~7~. ""■ .■iiii:,!.:i:iih,i.i..iiii. i.i.i ., ""' " l,umamX'lJ.ji. J'U^li^' ■■■ • ■■ iiiiiilniii-u:i-i;rn . i— valve view valve view, var. radians Notes : ^3 Fig. 55. Synedra nana, ( 5 ), cells 50-90u long, l-2u wide; striae very light, 25-30 in lOu. X 1000. Widely distributed. valve view Notes : Fig. 56. Synedra parasitica, ( 5 ), cells 10-25u long, 3-5u wide; striae delicate, somewhat radial, 16-19 in lOu. X 1000. Sometimes parasitic on Nitzschia sigmoides. valve Notes : views S. parasitica var. subconstricta Fig. 57- Synedra pulchella, (5 ), cells 33-150u long, 5-8u wide; about 12-15 striae in lOu (sometimes as many as 20); large clear refractive central area. X 1000. valve views C' -■■■■!■ ■ — - '■'!■'■■ 1 11 , ■; :■■■ ■ ,, ..... , -:■■•■' - :. , :- "■ l!' ■'■ I"-. \ S. putchella «» ARM mmm% var. lanceolata var. var. naviculacea form constricts minuta Notes : kh Fig. 58. Synedra rumpens, (5 ), cells 15-70u long, 2-3n vide; 19-20 striae in lOu; central area variable or completely absent. X 1000. valve views S. rumpens var. familiaris var. scotica »■■■ IffM l^H2SSS2E2=a var. fragilarioides Notes: Fig. 59. Synedra tabulata, ( 5 ), cells 60-150u long, 2-5u wide; striae short, 10-11*- in lOu. May form chains. X 1000. valve views TTmrnrnnrnmrr S. tabula ta var. fasciculata Notes : ^5 Fig. 60. Synedra ulna, (5 ), cells 50-350U long, 5-9P wide; striae delicate, distinctly punctate, 8-12 (usually about 10) in lOu; highly variable. X 600. Widely distributed. girdle view, S. ulna "in miiiniiMuiiMMi nut. miiMiiiMiiiMMii imm 111111 11 UMiiiiiilliimiimiiiiiiiiiil iiiiiimiimiiiiiiimiiiiiiiiiimiiiiiiiiiii iniiiiillllillllllllllimiMIIIIMIMIIIIIillliimiiiiiifc ' """"""'I'lHIIIIIllllllllllllllllllllllllllllllllnillllllllllllUmilllllll IIIIIHIIIIllllllllllllll'lllllll|||ill|llliHMIlliiliiilllll iiiiiii 11.11 mi i f.mTTfflllllllllMIIHIIIlllllllinillMHIIIIllMlllllillMlllllllllllllllllllllllllllllllllillllllllllllllllllllllllMllllllllllllllllllllllllllllllll n,-. *"""'""'"""""" iiniiiiiHIIIIIIIIIlllillllillllilllilliillltiliiiiii milllliillllli minimi liiiiiiiiiiiimiiinmJj valve views, S. ulna valve views var. oxyrhynchus ■giimiiiwiiiiimiii "•"-""uiuiiiiiiiii ..rflTTTTTTTTTTmTTTrTm — mTTTTTmTTTTTTmTmTth, ^llillllllllHIINiMii iiiiiiiiiiiiiiiiiiiiimpy gS5ss» var. oxyrhynchus , form contracta var. impressa Notes: k6 Fig. 6l. Synedra Vaucheriae , ( 5 ), cells 10-40u long, 2-k\s wide; 12-16 striae in lOu; central area clear and thickened only on one side. X 1000. Widely distributed. ^SHS> ^32STSS=== var. capitellata «ssSH!E3B&- c^TSI^ var- truncata valve views valve views, S. Vaucheriae Notes : Notes on other species of SYNEDRA. ^7 15a Raphe evident on at least one valve 16 15b Raphe not evident, concealed in a keel or wing 35 l6a Valves similarly ornamented, raphe on both valves 19 l6b Valves not similarly ornamented, raphe on one valve, opposing valve with pseudoraphe, or with rudimentary raphe near valve poles 17 17a Valves elliptical, never linear, sometimes bent along the apical axis - COCCONEIS Fig. 62. Cocconeis diminuta, ( 5 ), cells 7-15M long, 5- Central area not extending to the margins of the valve, striae present along lateral margins of the central area - NAVICULA 72 Fig. 109. Navicula bacillum, (5), cells 20-80u long, 10-20u wide; central area rounded not quadrangular; middle striae, 12-1^ in lOu, 18-20 striae in lOu near the poles; do not mistake for N. pupula. X 1000. valve view Notes ; Fig. 110. Navicula canalis, (2), cells 10-27u long, 3-5H wide; 16-18 striae in lOu. X 1000. valve view Notes : Fig. 111. Navicula conf ervacea , (k), cells 10-28u long, 5~8u wide; 18-22 striae in lOu; may be found in chains like Fragilaria; raphe can be seen in girdle view. X 1000. valve views girdle view Notes : 73 Fig. 112. Navicula contents, (5), cells 5-15H long, 2-3n wide. X 1500. May reach high numbers in southeastern brackish- water stations. valve views ' Illlllff N. contenta form parallela form biceps Notes Fig. 113. Navicula cryptocephala, (5), cells 20-^0u long, 5-7U wide; striae fine, 16-18 in 10u. X 1000. valve views N. cryptocephala Notes : var. veneta var. intermedia 74 Fig. 114. Navicula cuspidata, (5), cells 50-170U long, 17-37U wide; striae fine, 11-19 in 10^. X 1000. valve views N. cuspidata var. ambigua Wi mSijiii'M HHBi^ IBmm Notes : var. Heribaudi Fig. 115. Navicula exigua, (5), cells 10-35H long, 7-15U wide; 12-14 striae in lOu. X 1000. Notes 75 Fig. Il6. Navicula gastrum, (5), 25-60u long, 12-20u wide; 8-10 striae in 10u. X 1000. valve view Notes : Fig. 117. Navicula hungarica, (5), cells 10-30u long, ^-7n wide; 8-10 striae in 10|i. X 1000. Abundant in the southwest. valve views N. hungarica var. capitata Notes : 16 Fig. 118. Navicula mutica, (5), cells 10-kO\i long, 7-12u wide; 15-20 striae in lOu; single eccentric puncta in the central area. X 1500. valve view Notes Fig. 119. Navicula peregrine., (5), cells 50-150u long, 10-30u wide; 5-6 striae in 10\i. X 1000. Uiii|^l#ii/7 5lala|rM||i|iiyAs*e»*^ valve view Notes : Fig. 120. Navicula pupula, (5), cells 20-40u long, 7-10u wide; 22-26 striae in 10|i; no striae at the poles; central area quadrangular; can mistake for N. bacillum. X 1000. «r — : — •>, Notes : valve view var . capita ta 77 Fig. 121. Navicula pygmaea, (5), cells lO-^u long, Q-2k\i wide; about 26 striae in 10n. X 1000. valve view Notes Fig. 122. Navicula radiosa, (5), cells ^0-120u long, 8-20u wide; 10- 12 striae in lOu. X 1000. 5^ valve view Notes : Fig. 123. Navicula Reinhardtii, (5), cells 35-70u long, l4-20u wide; 7-9 striae in lOu. X 1000. valve view Notes 78 Fig. 124. Navicula tripunctata, (5), cells 35-60u long, 6-10u wide; 11-12 striae in lOu; central area quadrangular . X 1000. valve view Notes Fig. 125. Navicula viridula, (5), cells 36-80u long, 10-15H wide; 10 striae in lOu; central area rounded. X 1000. valve view Notes : Fig. 126. Navicula Zanoni, (6), cells 27-60u long, 7-Hu wide; 13-14 striae in lOu; can be confused with _N, cryptocephala . valve view X 1000 ii4!.*.51^*' " ** - £■» * ff r f 3 : i i i valve view X2000 Notes : 79 Notes on other species of NAVICULA. 80 35a Keel elevated into a lateral "wing" or flattened on the valve surface 37 35b Keel elevated into an axial "wing" extending along the central axis of the valve 36 36a Keel sigmoid, usually seen in girdle view (hour-glass-shaped), frustule twisted along the longitudinal axis; girdle broad with many longitudinal folds - AMPHIPRORA Fig. 127. Amphiprora alata, (5), cells *»-0-l60u long, 20-60u wide; striae fine,punctae discernable. X 1000. Abundant in the southwest. girdle view Notes : Fig. 128. Amphiprora paludosa, (5), cells 30-130u long, 15-50n wide; striae fine, punctae not discernable. X 1000. Abundant in the southwest. i - .-^^cffiffltoa*6 girdle view Notes : 81 Fig. 129. Amphiprora ornata, (5), cells 35-H5U long, 15-h0\i wide; appears to be twisted in girdle view. X 1000. girdle view Notes : Notes on other species of AMPHIERORA 82 36b Keel not sigmoid, girdle simple, not folded, keel eccentric - TR0P3D0NEIS Fig. 130. Tropidoneis lepidoptera, (9), cells 40-100u long, 10-15M- wide; girdle view easily confused with Amphiprora sp. X 2000. valve views girdle view Notes: 83 37a Valves with numerous internal transverse ribs extending completely across the valve 38 37b Valves without internal transverse ribs. ko 38a Raphe and axial area with "V"-shaped medial extension; with transverse septae appearing as costae and alternating with two or more rows of punctae - EPITHEMIA Fig. 131. Epithemia sorex, (12), cells 20-65u long, 8-15H wide; 5-7 septae in lOu; 12-15 punctae rows in 10n. X 1000. valve view Notes : girdle view Fig. 132. Epithemia turgida, (12), cells 60-220u long, 15-10u wide; 3-5 septae in lOu, 7-9 punctate rows in 10u. X 1000. valve view girdle view Notes: 8^ Notes on other species of EPITHEMIA. 38b Raphe and axial area without a "V "-shaped medial extension 39 39-a Raphe canal with pores, valves symmetrical to longitudinal axis - DENTICULA Fig. 133. Denticula elegans, (5), cells 15-40u long, 5-7U wide; 3-5 transverse ribs in lOu; 15-17 striae in lOu. valve view girdle view Notes : 39b Raphe canal without pores, valves asymmetrical to the longitudinal axis - RHOPALODIA Fig. 13k. 85 Rhopalodia gibba, (12), cells 35-300u long, 6-30u wide; 6-ti costae in lOu; 12-16 punctate rows in lOu. Notes : girdle view X 1200 valve view X 750 section of valve X 2000 Fig. 135. Rhopalodia gibberula, (5), cells 25-80u long, 12-kOji wide; 3-4 ventral costae in lOu, lk-1? punctate rows in lOu. X 1000. valve view var. van Heurckii Notes : girdle view 86 Notes on other species of RHOPALODIA. kOa Valves with lateral keel extending along both margins of each valve hi kOb Valves with lateral keel extending along one margin of each valve b-2 Ij-la Valve face longitudinally undulate, undulations conspicuous in girdle view; with "broad, short, peripheral costae; longi- tudinal pseudoraphe present - CTMATO PLEURA Fig. 136. Cymatopleura solea, (5), cells 30-300u long, 12-i+0u wide. X 750. valve view girdle view Notes 87 i<-Xt> Valve face not longitudinally undulate; valve face with longi- tudinal folds which appear as heavy costae, folds not conspic- uous in girdle view; girdle view rectangular, naviculoid, wedge-shapedjOr sigmoid; valve view linear, elliptical, ovate, or spirally twisted - SURIRF.T.TA wing Diagrammatic cross-section of Surirella, (7) Fig. 137. Surirella angustata, (5), cells l8-70u long, 6-20u wide; 6-9 longitudinal folds in lOu; striae delicate, the only "common" Surirella that is transversely symmetrical, X 1000. ^,. i,».,nh#„,, .„,,,, .,;;;>!,„, :uj m.vnl ;7Wff'7'i|l»'l|l!lip|fjffl;l;i|.;lTl'l't''Vl'l'-'|.!l,:1iJi ",' > ■■»"! anaa valve view ">J"" '■ .ll ,i m'mTmn iii i ■■"-•""" "- ^^^^^ girdle view Notes : Fig. 155. Nitzschia Lorenziana, (5), cells 65-l60p long, 3-5U wide; 6-8 carinal dots in 10n; striae distinct, 17-19 in 10»i. X 1000. CTl-UlllUlllllllli ■iillil^ valve view Notes Fig. 156. Nitzschia palea, (l2),20-65u long, 2-5H wide; 10-15 carinal dots in 10u; striae very fine, 35-^0 in 10|i. X 1000. Widespread. m^**-> valve view Notes : 95 Fig. 157- Nitzschia paradoxa, (5), cells 60-100u long, 4-6n wide; 6-8 carinal dots in lOu; 20-25 striae in lOu; do not confuse with N. dissipata. mm&E^^^^^ valve view X 1000 colony in girdle view X 500 Notes: Fig. 158. Nitzschia parvula, (5), cells 20-40|i long, 3-6u wide; 5-8 carinal dots in lOu; striae fine, 30-35 in lOu. X 1000. fJIIlI valve view Notes : Fig. 159- 96 Nitzschia sigma, (5), cells 50-70U long, 4-15u wide; 7-12 carinal dots in lOu; 22-30 striae in lOji. X 1000. I i l( I I I I I I II I I I 1 I 1 I I 1 I LU valve view Notes Fig. l60. Nitzschia sigmoidea, (3), cells l60-500u long, Q-lk-u wide; 5-7 carinal dots in 10m; striae distinct, 23-26 in lOu. "'"""""""liiiiii'iiifiniiiiiiiiii rr*~* "" ' ' ""'"^wm^ m.iiimnifi.iMf girdle view X 500 valve view X 1000 Notes Fig. l6l. Nitzschia sinuata, (5), cells 20-50u long, 5-8u wide; 5-6 carinal dots in 10n; about 18 striae in lOu. X 1000. valve views Notes : 97 Fig. 162. Nitzschia tryblionella, (5), cells 30-100^ long, 15-26^ wide; about 6 carinal dots in 10n; 5-7 ribs in lOu. X 1000. Notes: valve view var. victoriae Notes on other species of NITZSCHIA 98 42b Keels eccentric to the median axis, directly opposite; frustules rectangular in cross section, transversely striate or punctate, capitate ends, medianly constructed - HANTZSCHIA ] Diagrammatic cross-section of Hantzschia, (7) Fig. 163. Hantzschia amphioxys , (5), cells 20-lOOu long, 5-10u wide; carinal dots not elongate, 5-8 in lOu; 13-20 striae in lOu. X 1000. In the southwest. valve view Notes : Fig. 164. Hantzschia virgata, (5), cells 20-150U long, 6-12u wide; carinal dots elongate, k-6 in 10n; 9-15 striae in 10vi. X 1000. TTfpTTrr-^rrrffTffTT? valve view Notes s >> o c 0> > c o o Oh X Oh CO o I— ■< I— CO ■< CO s s r- z 5 5 ? 8 S § S S 3 p ?s a -3§ I 3 en n > a: *»>> • J S ... .< > 3o> I a" ™ r* ez -a oh x cif 5 wo H JO rn r-os a i-> o r > jo c*i z F* w SC z o ro > £ *-r*i >< z J> O Z E/5 X > O W O W O Z o < z a ii Co rnxciron CB C i- < > — — >5-I^H ^flMKHCC- i-t rp mzz>- rtoz>. z« -otnrc- w ?o z r> h h n z » r-37;x mnn cpw o r-H Mi-lrtO •- >H><->r- >0"«OhH h £ r"ZZ< wfeO 0ViO03 30 > C Z • z - 30 > C Z H 3D x Z h r > ob H I "0 'JMfiOOSW i o o> > c m >- c ' x h h o> > xx x -- c r* w c w h 50 in z- 53 £ 5 » 5 73 KiE n z-i C ra lo r z PS ("■OK >0 O-p-T! O O t> d HO OOP1 X W n2 r-r- ozz !> o n ' >c rno h 3» 2 3 — > r* H 30 HW O h > > C OC1H X X Irt Fle-O O i- H Z Q [- 3 n O O O O .1 T*" > >C>{>C~4>CH'> — * -i - — in -- - * » --!► *• s £ S Achnanthes lanceolate Achnanthes minutlsslma Amphiprora a lata Amphiprora paLudosa Amphora avails Anomoeonels exllls Asterionella formosa BaciLlarla paradoxa Blddulphia laevls Ca Lone Is amphisbaena Ceratoneis arcus Cocconels pedlculus foe cone is placentula Cosclnodlscus rothll Cyclocella atomus Cyclotella cotnta Cyclotella gLomerata Cyclotella kutzlnglana Cyclotella meneghlnlana Cyclotella ocellata Cyclotella pseudostel Ugera Cyclotella stellLgera CycLotella striata Cymatopleura solea Cymatoslra belgica Cymbella affLnls Cymbella prostrata CymbeLla tumida Cymbella ventrlcosa Diatoma anceps Diatoma elongation Diatoma vulgare Dlplonels smtthii Eplthemta turglda Eptthemia sorex Fragllaria brevlstrlata Fragllaria capucLna Fragllaria construens Fragllaria crotonensls Fragllaria leptostauron Fragllaria plnnata Gomphonela herculean* Comphonema ollvaceum Gomphonema parvulum Cyroslgma kutzLngll Hantzschla amphloxys Meloslra amblgua Meloslra blnderana o C5 s a s s 5 S .< > » > > a: oo C 1-1 ?J 70 mpw oh> o co li >CM<> .- .- 3> £ n z z > m -- h H n z » Z < trt W O O V t] i-5 m«2h HOZ (/> JO flf" mo-hH Z -0-- x or »zh(ii re- s' m . _ ass*- gp „ > ojo ' o com n W I'J 1 * >i *. ^ - Z Z O O T5 W - 3»cz« " Z t*l 5* - c mo z r* ;r 35 5 5 >I fl> > O O -0 "3 o om =: oz z £ _ ££ ;§8P < ft r 3 £ It *> C> • o o o o -j w z z z z H H H H O O O O 3333 m R Pi m H H -J H R w R w - H -J H *- - -T« ' -,H H w \ 1 H ' -1 ^ f- —* - 1 *- [ [ < •f •{ >c -t TT ^^~ >t ■c C H f >c H H M H h: 1 -I >( >J*c-c hL >t Meloslra dlstans alplgena Meloslra granulate M, granulata angustlsstma Melosira lalandlca Meloslra Itallca Meloslra varlans Merldlon clrculare Navlcula canalls Navlcula cryptocephala Navlcula cuapldata Navlcula lncomposlta Navlcula not t i,i Navlcula trlpunctata Navlcula virldula Nltzschla aclcularls Nltzschla aplculata NLtzschla denclcuLa Nlczschla dissipate Nlczschla fonClcola Nltzschla holaatlca Nltzschla hungarlca Nltzschla linearis Nltzschla slgma Nlczschla slgmoldea Nlczschla trybllonella Plnnularla borealls Pleurosigma dellcaCulum Rholcosphenla curvaCa Rhtzosoienla erlensls Rhopalodla glbba S. astraca mlnutula Stephanodlscus dublus Stephanodlscus hantzschla Scephanodlscus nlagarae S. nlagarae var. magnlflca Stephanodlscus tenuis Surlrella angustata Surlrella brlghtwellll 'Jurlrella ovata irurlrella etrlatula Synedra acus Synedra pulchelLa Synedra nana Synedra tabulata Synedra ulna Synedra vaucherlae labellarla fenescraca Tabellarla t locculosa ft b a U. S. GOVERNMENT PRINTING OFFICE : 1966 O - 220-505