PLANKTON OF THE JAPANESE COAST. 



145 



all, it seems to me that such characters as the length of horns or the 

 manner of curvature in their course, unless exceptionally pronounced, are 

 by themselves altogether too unsafe features to base specific distinction 

 on. Of much greater importance for the purpose seem to me to be the 

 general form and rigidity of body as well as the angular flexure and the 

 direction of horns at origin. Basing myself on this standpoint, I venture 

 to put down the following comparative table between the Ceratium species 

 described or mentioned by Schröder (left column) and those set forth by 

 me in the present paper (right column). 



Ceratium subcontortiim Schrödcr= (7. contortimi (Gourr.) Cleve 



(Pl. III, fig. 4). 

 ( '. saltans Schröder=C gibberum Gourr. (Pl. III. fig. 3). 

 C. ( ~>ka murai Schroder = probably C. horridum f. (Pl. IV, fig. 21/;). 

 C. aequatoriale Schröder = a form of C. vultur Cleve (e.g. the lower 



one of two shown in PL III, fig. 1). 

 C. ceylanicum Schröder =£7. patent issinmm Ostf. and Schm. 



(PL III, fig. 2). 

 C. elegans Schröder= C. patent issinmm Ostf. and Schm. 



(PL III, fig. 2) 



C. Hundhauseni Sehr öder —C. volans Cleve (PL IV, fig. i8r). 



C. patinatimi Schröder = probably C. ranipes Cleve (PL III, fig. 6). 



Pyrocystis hamulus Cleve var. semicircular is Schröder = P. /i a main s f. 



