DINOFLAGELLATA 259 



P. divergens (E.) (Fig. 110, d). About 45ju in diameter; yellowish, 

 salt water. 



Genus Ceratium Schrank. Body flattened; with one anterior and 

 1-4 posterior horn-Uke processes; often large; chromatophores yel- 

 low, brown, or greenish; color variation conspicuous; fission is said 

 to take place at night and in the early morning; fresh or salt water. 

 Numerous species; specific identification is difficult due to a great 

 variation (p. 176). 



C. hirundinella (Miiller) (Figs. 85; 110, e). 1 apical and 2-3 anta- 

 pical horns; seasonal and geographical variations (p. 177); chain- 

 formation frequent; 95-700iu long; fresh and salt water. Numerous 

 varieties. 



C. longipes (Bailey) (Fig. 110, /). About 210m by 51-57^; salt 

 water. 



C. tripos (Muller) (Fig. 110, g). About 225/x by 75m; salt water. 

 Wailes (1928) observed var. atlantica in British Columbia; Martin 

 (1929) in Barnegat Inlet, New Jersey. 



C.fusus (Ehrenberg) (Fig. 110, h). 300-600m by 15-30m; salt water; 

 widely distributed; British Columbia (Wailes), New Jersey (Martin), 

 etc. 



Genus Heterodinium Kofoid. Flattened or spheroidal; 2 large 

 antapical horns; annulus submedian; with post-cingular ridge; sulcus 

 short, narrow; shell hyaline, reticulate, porulate; salt water. Numer- 

 ous species. 



H. scrippsi K. (Fig. 110, i). 130-155m long; Pacific and Atlantic 

 (tropical). 



Genus Dolichodinium Kofoid and Adamson. Subconical, elongate; 

 without apical or antapical horns; sulcus not indenting epitheca; 

 plate porulate; salt water. 



D. lineatum (Kofoid and Michener) (Fig. Ill, a). 58m long; eastern 

 tropical Pacific. 



Genus Goniodoma Stein. Polyhedral with a deep annulus; epi- 

 theca and hypotheca slightly unequal in size, composed of regularly 

 arranged armored plates; chromatophores small brown platelets; 

 fresh or salt water. 



G. acuminata (Ehrenberg) (Fig. 111,6). About 50m long; salt water. 



Genus Gonyaulax Diesing. Spherical, polyhedral, fusiform, 

 elongated with stout apical and antapical prolongations, or dorso- 

 ventrally flattened; apex never sharply attenuated; annulus equa- 

 torial; sulcus from apex to antapex, broadened posteriorly; plates 

 1-6 apical, 0-3 anterior intercalaries, 6 precingulars, 6 annular 

 plates, 6 postincingulars, 1 posterior intercalary and 1 antapical; 



