362 UnivrrsiUj of Calif orvia Publications in Zoology. \y°^- * 



and appears occasionally in most of the spctnrs luiviiij? elongated 

 slender horns. I have observed it, for example, in ('■ loiuiipnx, 

 C. iittf)-)iif(Jiu7n, C. protuherams (fig. 20), C. macrorfros, C. os- 

 tcnfehli. C. viillur, C. iv/lexum, (!. cariinisr, ('. tr'ipos, ('. (irciui- 

 tiini (figs. 11, 12, 26), a. srln-dhki, (!. azoriimii and '". hrlrro- 



Figs. 16-19. — Ventral views of Ceratium trichoceros showing progressive 

 and proportionate reduction of the antapical horns in autotomy. X 220. 

 The form of the end of the horns after autotomy is shown under greater 

 magnification in supplementary sketches in connection with figure 17. 



camptum. It occurs also in the long-horned members of the sub- 

 genus Amphiceratium such as C. exicnsum and C. biceps (figs. 

 21-24) . It is, however, relatively rare among the species of the 

 subgenus Biceratium such as C. furca, C. lincatiim and C. ewgram- 

 WM-m, where the antapical horns, and the apical also as a rule, 

 are relatively short and play a less important part in the economy 

 of flotation than they do in the long-horned species of the sub- 

 genera Euceratium and Amphiceratium. 



