172 bulletin: museum of comparative zoology. 



parallel direction any considerable distance, and are not so much incurved as 

 they frequently are in C. platycorne. The antapicals are flattened, of uniform 

 width, or expanded very slightly towards the antapex. The tips are rounded, 

 squarish, or truncate, rarely asymmetrically pointed. 



Length, 95-135 jx ; greatest lateral extension, 65-90 /x. 



Station, 4732. 



Ceratium lanceolatum, sp. nov. 



Plate 3, Fig. 17. 



A small species related to C. furca, without differentiated apical horn. 



The epitheca is not constricted to form an apical horn, but the midbody ex- 

 tends to the apical pore or nearly to it. The apical pore is oblique or strictly 

 terminal. The sides of the epitheca are convex, or in some cases slightly con- 

 cave distally on the left side, as in C. scapiforme. 



The hypotheca is low, its axial altitude equalling or exceeding the transdi- 

 ameter. Antapicals short, stout, and straight, the right about half the length 

 of the left. 



Length, 95-122 /^i; transdiameter, 19-22/*. 



Stations, 4717-4719. 



Ceratium pennatum, sp. nov. 



Plate 2, Figs. 12, 13, 14. 



An elongated species of the G furca group with elongated left antapical curved 

 to the left and dorsally. Long apical, which is straight or curved evenly and 

 but slightly to the left. Short right antapical usually present. An exceedingly 

 variable species. 



The midbody is quite variable in form, scarcely swollen in some cases, and 

 merging gradually into the stout apical horn (propria, forma nov., Plate 2, 

 Tig. 12) or more or less swollen, both hypotheca and epitheca being enlarged 

 as they approach the girdle, and more or less sharply delimited from the horns 

 in which they are continued (inflata, forma nov., Plate 2, Fig. 13). The spe- 

 cies also varies in the curvature of the left antapical. This is gradual and dis- 

 tributed throughout most of the length in many individuals. In others it is 

 limited to a short abrupt curve at the antapex (falcata, forma nov., Plate 2, 

 Fig. 14). This form is, as a rule, about half the size of f. propria, and may 

 prove to be a distinct species. The length of the right antapical is also subject 

 to great variation, being usually fairly well developed, though rarely attaining 

 to a length of 0.5 of a transdiameter. 



The concave faces of the curved horns are often greatly thickened in both the 

 apical and left antapical. 



This species differs from G. striatum (Okamura and Nishikawa) in the curva- 

 ture of its horns, and from G bigelowi, sp. nov. in the fact that its greatest 

 transdiameter is at the girdle or very close to it. 



Length, 360-1225 /a; transdiameter, 25-50 p. 



At many stations between 4574-4684. 



