1911] Kofoid: The Genus Gonyaulax. 207 



The pJaie formula is 3', /", G" , 6, 6'", IP, 1"". The apical plates, 1' 

 to 3' surround the apex. Apical 1' is a slender plate reaching to the 

 ventral area, separating plates 1" and 6" of the precingular series and 

 bearing at its apex the elliptical closing platelet, a thin scale-like struc- 

 ture which covers the so-called apical pore, and when the plates are 

 parted often remains attached to the slender midventral apical plate 1'. 

 Plates 2' and 3' are nearly bilateral and placed saddle fashion upon the 

 anterior end. The anterior intercalary is a small plate not touching the 

 apical region and lying to the right (of body, left of figure) of apical 1', 

 and between the apical and precingular series. It bears on its median 

 margin a conspicuous pore, which is present throughout the genus Gonyau- 

 lax, and has not been noted heretofore, which I call the ventral pore. 

 The six precingulars l"-6" are all prominent plates, 6" being quadrangular. 

 It is triangular in most species which have widely displaced girdles. The 

 girdle plates are normally six in Gonyaulax but were not separated in 

 this species as the material at command was limited. The six postcingu- 

 lars are typical; postcingular 1' being, as usual, a narrow plate partially 

 hidden on the left margin of the longitudinal furrow. The posterior inter- 

 calary IP is a wide plate at the left of the longitudinal furrow, touching 

 neither the girdle nor the antapex. The single antapical 1"", is a large 

 pentagonal plate whose ventral margin is slightly indented by the ventral 

 area. 



The ventral area includes those plates of the thecal wall which are 

 involved in the longitudinal furrow. There are as many as six of these 

 in some species of Gonyaulax. Only the most anterior one is to be seen 

 in the figure. 



The surface of the San Diego specimen was perfectly smooth and was 

 sparsely porulate with rather large scattered pores. There were no sur- 

 face markings or reticulations and the lists along the furrows were with- 

 out ribs. 



Cell contents unknown. 



Dimensions : Length, 43|U. ; transdiameter, 38fx ; dorsoventral 

 diameter the same ; girdle width, 4.5|U. 



Comparisons : Its spherical form and smooth surface at once 

 distinguish it from all described species of the genus. 



Described from' an empty theca taken in surface plankton off 

 San Diego, November 26, 1904. The composition of the plankton 

 in this collection indicates its oceanic and subtropical origin as 

 shown by the presence of such species as Pijropliacus horolo- 

 giciim, Cerotocorijs armatiim-, C. horrida, Gonyaulax turhynei, 

 Ceratium rcticidatum and Poelolampas pahnipes. 



b). The Spinifera Group 

 A group of rotund species characterized by the presence of 

 one or more antapical spines, more or less widely displaced 



