1908] Kofoid. — Notes on Species of Ceratium. 389 



Ceratium seta (Ehrbg.). 



Ehrenberg ('60), p. 792, as Peridiniwm Seta. 



Ehrenberg ('74), p. 3, Taf. (1), fig. 1, aa Peridiniwm Seta. 



Saville-Kent ('80- '81), p. 457, as Cemlium seta. 



Stein ('83), explanation of Taf. 15, as a synonym of C. fusus. 



A careful examination of the species of the Ceratium fusus 

 group which I have recently made at San Diego convinces me 

 that Ehrenberg was correct in distinguishing G. seta as a species 

 distinct from C. fusus. 



Ceratium seta has a less broadly fusiform midbody, its trans- 

 diameter averaging 10 /x less than that of C. fusus. Its surface 

 is less rugose, its curvature usually more pronounced, and its 

 right antapical uniformly suppressed, whereas this horn is short 

 but uniformly present in C. fu^us. Another striking difference 

 lies in the fact that the hypotheca exceeds the epitheca in the 

 former species, but these relations are reversed in C. fusus. 



Gourret (83) describes, as (' fusus var. cxtcnsum and G. 

 longirostrum. certain long-hnrned fonns resembling C. seta. A 

 statistical study of material from the oceanic plankton off San 

 Diego leads me to regard these as forms of one species, G. exten- 

 sum (Gourret), which, however, is distinct from C. seta. 



Ceratium biceps Claji. et Lachm. 



Claparfide et Lachmann ('58- '59), pp. 400-401, pi. 19, fig. 8. 

 Gourret ('83), pp. 55-5(5, pi. 1, fig. 19, as C. Berghii. Symmetry 



reversed in figure. 

 Okamura and Nishikawa (:04), p. 128, pi. 6, fig. 25, as C. fusus 



var. stricta nov. var. prov. 

 Kofoid (:07), p. 133, as C. strictum. 

 Kofoid ('08), p. 00, figs. 21-24, as C. biceps. 



In my opinion Claparede and Lachmann described as G. biceps 

 an individual which had recently undergone autotomy and had 

 in consequence relatively short apical and left antapical horns. 

 Their figure will bear the closest comparison with such mutilated 

 specimens. Later Gourret ('83) gives a reversed figure which 

 may be referred provisionally to this species. Okamura and 

 Nishikawa ( :04) were the first to publish a typical figure showing 

 the normally developed horns, but they did not recognize the 

 similarity of the species with which they were dealing to that 



