1911] Kofoid: The Genus Gomjaulax. 235 



Comparisons: See G. poly gramma (p. 229). Distinguished 

 readily from G. polygramma by its larger size, greater antapical 

 asymmetry and elongation of apical region ; from G. pacifica by 

 its smaller size, greater rotundity at girdle and oblique antapex. 



Distribution : Taken at San Diego, November 12, 1904, in 

 surface plankton seven miles WNW of Point Loma. This 

 collection contained also G. pacifica, Ceratium triclioceros and 

 Ceratocorys armatmn, all tropical species. Reported by Pavil- 

 lard (1909) in the winter plankton of the Gulf of Lyons. 



10. Gonyaulax pacifica Kofoid 



PI. 15, fig. 35 



Gonyaulax pacifica Kofoid (1907), p. 308, pi. 30, figs. 37-39. 

 Steiniella cornuta Karsten (1907), pp. 348, 420, pi. 53, fig. 7. 



Diagnosis: An exceedingly large species, resembling G. poly- 

 granifna Stein, asymmetricall}' flattened and excavated on the 

 ventral face, in ventral view more rounded especially on post 

 margin than in G. kofokli Pavillard, linear markings less regular 

 and usually less developed than in G. polygramma, posterior 

 intercalary very narrow, its length five to seven times its width. 

 Proximal end of girdle curved posteriorly. 



Description: The largest known species of the genus, its outline 

 varying greatly with the point of view. Seen in ventral view the body 

 resembles G. polygramvia and G. kofoidi but is usually more rotund pos- 

 teriorly, the sides of both epitheca and hypotheca being convex, with 

 some contraction near the apex. Occasional specimens have straight or 

 concave or even slightly angled slopes of the epitheca. The striking 

 feature of the species is the broad, deep asymmetrical excavation of the 

 ventral face, principally upon its right side, which extends posteriorly to 

 the thin postmargin giving almost the shape of a scoop to deeply exca- 

 vated individuals and an asymmetrically reinform cross-section at the 

 girdle, as well as a much modified lateral profile. Because of this asym- 

 metry it is rather difficult to get strictly ventral or lateral views of the 

 theca, our figure (pi. 15, fig. 35) giving an obliquely ventral view with 

 greater exposure of the left face. G. polygramma and G. Jcofoidi approach 

 more nearly to a circular cross-section at the girdle. In this species the 

 dorso-ventral diameter is from 0.6 to 0.75 of the transdiameter. 



The length, excluding spine, is 1.6 to 2 transdiameters (used in this 

 description for the greatest diameter at the girdle which is somewhat 

 oblique to the true transdiameter). The epitheca is contracted distally 

 to a short, scarcely differentiated ^.pical horn about two girdle widths 

 in length and obliquely truncated. It is deeply and abruptly concave 

 above the girdle on the ventral face. Its altitude is from 0.78 to 1.16 



