388 University of California Publications in Zoology. [Vol.4 



and P. Seta, to a synonym of C. fustis, in the explanation of his 

 Tafel 16, while P. eugrammnm is referred to C. furca, in the 

 explanation of his Tafel 15. 



It is not improbable that the reduction of these species of 

 Ehrenberg's to synonyms by Stein ( '83) is due to Stein's knowl- 

 edge only of an earlier paper of Ehrenberg's ('60) in which he 

 briefly diagnosed these species, but without figures, in the absence 

 of which their recognition is difficult, if not impossible. Later 

 authors have, with the exception of Saville-Kent ('81- '82), con- 

 curred in Stein's opinion. 



I have elsewhere ( :07) noted the correctness of Ehrenberg's 

 recognition of C. eugrammnm. I wish here to revive tM^o of his 

 other species of Ceratium, which are equally valid, and to note 

 the instances in which several of them have crept into literature 

 under new names in recent years. 



Ceratium trichoceros (Ehrbg.). 



Ehrenberg ('60), p. 791, as Peridinium Trichoceros. 



Ehrenberg ('74), p. 3, Taf. (1), fig. 1, as Peridinium Trichoceros. 



Saville-Kent ('80- '81), vol. 1, p. 457, as Ceratium seta. 



Stein ('83), explanation of Taf. 16, as a synonym of C. tripos. 



Karsten (:06), Taf. 22, fig. 31b, as C. flagelliferum Cleve; fig. 

 32a and b, as C. fiageUiferum forma crassa n. var. The latter 

 figure is questionably referred to C. trichoceros by me. 



Kofoid (:08), p. 362, figs. 15-19. 



This species of Ehrenberg's is well defined by its rigid habit 

 of growth, the wide-spreading major flexures of the antapicals. 

 and the slender horns with pointed closed tips. Its three horns 

 are subparallel and the antapicals are usually noticeably serrate 

 along their posterior margin tow^ard their major flexures. 



It has probably been confused in the past with C. flagelli- 

 ferum Cleve ( :00), a form of C. inflexum Gourret ('83), Avhieh 

 has more flexible or variously incurved or recurved antapicals 

 and exhibits in general a more lax habit of growth than C. tri- 

 choceros. The tips of the antapicals of C. inflexum are con- 

 tracted, usually have a small terminal pore and are sometimes 

 swollen, difi'ering in these particulars from the pointed closed 

 tips of C. trichoceros. C. inflexum also lacks, as a rule, the 

 prominent posterior, serrations of C. trichoceros. 



11 



