DINOFLAGELLATA 253 



G. aeruginosum S. (Fig. 108, a). Chromatophores green; 33-35^ 

 by 22/x; ponds and lakes. 



G. rotundatum Klebs (Fig. 108, b). 32-35^ by 22-25^; fresh water. 



G. palustre Schilling (Fig. 108, c). 45/Lt by 38/x; fresh water. 



G. agile Kofoid and Swezy (Fig. 108, d). About 28m long; along 

 sandy beaches. 



Genus Hemidinium Stein. Asymmetrical; oval; annulus about 

 half a turn, only on left half. One species. 



H. nasutum S. (Fig. 108, e). Sulcus posterior; chromatophores 

 yellow to brown; with a reddish brown oil drop; nucleus posterior; 

 transverse fission; 24-28m by 16-17^; fresh water. 



Genus Amphidinium Claparede and Lachmann. Form variable; 

 epicone small; annulus anterior; sulcus straight on hypocone or also 

 on part of epicone; with or without chromatophores; mainly holo- 

 phytic, some holozoic; coastal or fresh water. Numerous species. 



A. lacustre Stein (Fig. 108, /). 30/i by 18^; in fresh and salt (?) 

 water, 



A. scissum Kofoid and Swezy (Fig. 108, g). 50-60/x long; along 

 sandy beaches. 



A. fusiforme Martin. Fusiform, twice as long as broad: circular 

 in cross-section; epicone rounded conical; annulus anterior; hypo- 

 cone 2-2.5 times as long as epicone; sulcus obscure; body filled with 

 yellowish green chromatophores except at posterior end; stigma dull 

 orange, below girdle; nucleus ellipsoid, posterior to annulus; pellicle 

 delicate; 17-22^ by 8-1 1/x in diameter. Martin (1929) found that it 

 was extremely abundant in parts of Delaware Bay and gave rise to 

 red coloration of the water ("Red water"). 



Genus Gyrodinium Kofoid and Swezy. Annulus descending left 

 spiral; sulcus extending from end to end; nucleus central; pusules; 

 surface smooth or striated; chromatophores rarely present; cyto- 

 plasm colored; holozoic; salt or fresh water. Many species. 



G. biconicum K. and S. (Fig. 108, h). 68ju long; salt water; off Cali- 

 fornia. 



G. hyalinum (Schilling) (Fig. 108, i). About 24/u long ; fresh water. 



Genus Cochlodinium Schutt. Twisted at least 1.5 turns; annulus 

 descending left spiral; pusules; cytoplasm colorless to highly colored; 

 chromatophores rarely present; holozoic; surface smooth or striated; 

 salt water. Numerous species. 



C. atromaculatum Kofoid and Swezy (Fig. 108, j). 183-185ju by 

 72m; longitudinal flagellum 45m long; off California. 



Genus Torodinium Kofoid and Swezy. Elongate; epicone several 

 times longer than hypocone; annulus and hypocone form augur- 



