196 University of California Puhlications in Zoology. [Vol.8 



reported five and though Biitschli (1885b) later reported six in 

 G. polyedra, no one has presumed to question the accuracy of 

 Stein's observations, so great has been the confidence placed in 

 his work which as a rule is extremely detailed and reliable. Leni- 

 mermann (1907) figures and describes six precingular (Prae- 

 aequatorialplatten) in Gonyaulax palustris. 



The girdle plates {1-6) are six in number and may be disartic- 

 ulated from one another with comparative ease. 



The postcingular plates {l"'-6"'. fig. B) are invariably six in 

 number, plate i"' of the series lying immediately adjacent to the 

 ventral area (on its left edge) as a slender linear structure. This 

 plate has hitherto been overlooked, though Entz (1904, fig. 4a. f) 

 delineates it but does not otherwise note its presence or signifi- 

 cance. Paulson (1904) indicates it in his figure of (i. friacantha 

 but does not otherwise note its presence. Lemmermann (1907) 

 figures six postcingulars in G. palustris (in his fig. 5) but states 

 that there are five "Postaequatorialplatten," no one of which can, 

 however, be homologized with the narrow postcingular J' of my 

 nomenclature. 



The posterior intercalary (P') and anfapical (1"", fig. B) 

 are invariably present without change in number in the different 

 species and the latter constitutes the most ready means of separa- 

 tion of this genus from most of the genera of the Peridinidae. 



II. Generic Di.vgnosis 



Gonyaulax Diesing emend. 



Body variously shaped, s])heroidal, polyhedral, l)roadly fusi- 

 form, elongated with stout apical and antapieal prolongations, 

 or dorso-ventrally flattened. Apex rounded or truncate sym- 

 metrically or asymmetrically, never acutely symmetrically 

 pointed. Antapex rounded, flattened, or pointed symmetrically 

 or asymmetrically. Girdle usually equatorial, descending, dis- 

 placed distally one to seven times its own width, and sometimes 

 with slight overhang. Transyerse furrow impressed or not ; longi- 

 tudinal furrow usually slightly indenting the epitheca, often 

 flaring distally, well developed, reaching to or approaching the 



