1911] 



Kofoid: The Genus Gonyaulax. 



195 



calaries (P-S"), as well as other plates lying between the apical 

 and precingular series. 



The precingular plates il"-6", fig. A) are invariably six in 

 number in the species which I have examined. Stein (1883) 



Figs. A-D. Plates of thecal skeleton of Gonyaulax spinifera (Clap, et 

 Lach.) Diesing X 1000. A, dorsal view; B, ventral view; C, antapical 

 view; D, apical view. 1-6, girdle series of plates; I'-S', apical series; 

 l"-6", precingular series; l"'-6"', antapical series; IP posterior inter- 

 calary; 1"", antapical plate; ant. pi., anterior plate of ventral area; ant. 

 sp., antapical spine; cl. pi., closing platelet of apex; f. I., fission line along 

 which skeleton parts in cell division; ft. po., flagellar pore; int. pl., inter- 

 mediate plates (usually four in number, hidden in constricted region of 

 ventral area); post, pl., posterior plate of ventral area; v. a., ventral area 

 ("longitudinal furrow" of other writers in part) ; v. po., ventral pore. 



