COSMAEIUM. 77 



gular, ends retuse, sides slightly convex or straight, inferior 

 angles obtuse ; above the middle a single large granule and 

 below it a series of six small granules arranged in a semi- 

 circle, ends tending towards the retuse apex ; viewed from 

 apex oval, from sides subcircular. Membrane smooth. 

 Diameter of cell 24 //. ; length 32 ju. 

 Pond, Tewksbury, Mass. 



C. DoNNELLii, Wolle. Plate XIX, figs. 41, 42. 



Cells nearly as long as wide, suborbicular ; sinus narrow, 

 gaping ; semi-cells somewhat flattened, semicircular with 

 angles rounded; margin formed of about eighteen large 

 pearl-like granules ; area smooth with a series of three larger 

 granules, or papillae in the center. End view oval, three 

 papillae on each side. 

 Diameter 37-45 /<. 



Found in collections made by J. Donnell Smith in Florida, 

 1879. 



C. TAXiCHONDEUM, Lund. Plate XIX, figs. 32-34. 



Cells suborbicular, slightly longer than broad ; sinus deep, 

 narrow, linear, barely widened at the mouth; semi-cells 

 semicircular, margin of base nearly straight, membrane 

 thickened at the angles ; face ornate with a single large 

 granule at the isthmus, and two somewhat arched rows near 

 the dorsal margin, one with three and the other with five 

 or six granules ; seen from the vertex, elliptic with five or 

 six granules on each side; cytioderm punctate; isthmus 

 one-fourth of the diameter of the cell. Chlorophyl nuclei 

 two. 



Diameter 40-50 ^. 



Occurs frequently in ponds, northern New Jersey, Penn- 

 sylvania and Massachusetts. 



^ar. BIDENTULTJM, Lagh. Plate XLIX, figs. 17, 18. Distinguish- 

 ing feature ; in vertical view elliptic, somewhat contracted at 

 ends, the angles bidentate. 



C PSEUDOTAXICHONDETJM, Nord. Plate XLIX, figs. 22, 23. 



Scarcely as long as broad, deeply constricted, sinus con- 

 siderably widened outwardly; semi- cells semicircular with 

 the middle more or less truncate or depressed ; the angles 

 somewhat thickened and often terminating in a tooth-like 

 point ; above the basal line is an arched transverse series of 

 four granules ; end view elliptical with four granules on each 



