DINOFLAGELLATA 223 



finger-like mobile tentacle directed posteriorly; salt water. One 

 species. 



P. tentacuUfera K. et S. 58// by 27m; pale yellow; off California. 



Family 5 Gymnodiniidae Kofoid 



Naked forms with simple but distinct 1/2-4 turns of annulus; 

 with or without chromatophores; fresh or salt water. 



Genus Gymnodinium Stein. Pellicle delicate; subcircular; bi- 

 laterally symmetrical; numerous discoid chromatophores vari- 

 colored (yellow to deep brown, green, or blue) or sometimes ab- 

 sent; stigma present in few; many with mucilaginous envelope; 

 salt, brackish, or fresh water. Numerous species. 



G. aeruginosum S. (Fig. 102, a). Chromatophores green; 33-35/x 

 by 22m ; ponds and lakes. 



G. rotundatum Klebs (Fig. 102, 6). 32-35m by 22-25^; fresh wa- 

 ter. 



G. palustre Schilling (Fig. 102, c). 45m by 38m; fresh water. 



G. agile Kofoid et Swezy (Fig. 102, d). About 28m long; in sandy 

 beaches. 



Genus Hemidinium Stein. Asymmetrical; oval; annulus about 

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



H. nasutu7n S. (Fig. 102, e). Sulcus on hjrpocone; chromato- 

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

 posterior; transverse fission; 24-28m by 16-1 7m; fresh water. 



Genus Amphidinium Claparede et Lachmann. Form variable; 

 epicone small; annulus anterior; sulcus straight on hypocone or 

 also on part of epicone; with or without chromatophores; mainly 

 holophytic, some holozoic; coastal or fresh water. Numerous spe- 

 cies. 



A. lacustre Stein (Fig. 102, /). 30m by 18m; in fresh and salt (?) 

 water. 



A. scissum Kofoid et Swezy (Fig. 102, g). 50-60m long; in 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; 17-22m by 8-1 1m in diameter. Martin 

 (1929) found that it was extremely abundant in parts of Delaware 



