290 University of California PuMications in Zoology. [Vol. 8 



in the latter genus plate 1" is triangular or pentagonal and usu- 

 ally small. In Gonyaulax and in Levander's species 1" is quad- 

 rangular and large. 



The girdle plates (1-6) in Gonyaulax and in Levander's 

 species are six in number with sutures approximately those of 

 the two adjacent series in location. In Peridinium there are 

 three with no dorsal sutures. 



There are six postcingulars {l"'-6"') in Gonyaulax and in 

 Levander's species, and but five in Peridinium. Postcingular 

 i'" in Gonyaidax is a very small plate, in Peridinium it is rela- 

 tively much larger. In Levander's species it is relatively smaller 

 than in any species of Peridi)iiu)n, though still unusually large 

 for Gonyaidax. 



In Levander's species and in Gonyaulax there is always pres- 

 ent a posterior intercalary plate, 1''. This is absent in Peridin- 

 ium, though possibly represented by the left antapical. 



In Peridinium there are two nearly symmetrically placed 

 antapical plates, in Gonyaulax and in Levander's species there is 

 but a single median one 1"". 



The ventral area of both Peridiuiu)n and Gonyaulax consists 

 of an anterior and posterior plate, with several intermediate 

 plates between. These plates in Levander's species much 

 resemble those in those species of Gonyaulax in which the ventral 

 area is wide and nearly straight as in G. jjolyedra and G. tria- 

 cantha. The anterior plate is deeply notched by the flagellar 

 pore (pi. 18, fig. 5) and the ventral area widens into the posterior 

 plate as in G. triacantlia. This plate is, however, relatively much 

 Avider in Levander's species than in any other species of Gonyau- 

 lax. Peridinium usually has a ventral notch at the apex while 

 this is not found in any species of Gonyaidax nor in Levander's 

 species. The ventral pore so generally present in Gonyaulax is 

 not found in Peridinium and appears to be lacking in Levander 's 

 species, in which, however, the general porulation is greatly 

 reduced. 



From the facts detailed above I conclude that this interesting 

 species of Levander's belongs in the genus Gonyaidax rather 

 than in Peridinium. A brief description is here appended. 



