Vol. 3] Kofoicl. — Dinoflagellata — New Species. 303 



A delicate species of the macroceros section with deep post- 

 indentation and left antapical passing posteriorly from the mid- 

 body for a short distance before curving in the major flexure. 

 Both antapicals are convex outwardly. 



The midbocly is smaller and more rotund than in C. macro- 

 ceros narrowing abruptly into the erect submedian apical horn. 

 The girdle is relatively high, passing some distance above the base 

 of the right antapical. The postindentation is very deep, usually 

 exceeding 0.5 of a transdiameter, and the postobliquity (24°) is 

 less steep than in C. macroceros and is set off abruptly from the 

 bases of the antapical horns. The major flexures are more abrupt 

 and the distance between the shoulders is less, in absolute dis- 

 tance, than in C. macroceros. The antapicals spread distally in 

 a relatively wide antapical angle which is greater in short-horned 

 (54°-103°) than in long-horned (51°-78°) individuals. Both 

 horns are convex outwardly but the right is usually less curved 

 than the left and often shorter. 



The thecal wall is delicate and hyaline and the girdle is often 

 incomplete distally. 



Length, 250-480/^; transdiameter, 50-60/x; distance between 

 arms at girdle, 215-295/x ; at tips, 300-480/x. 



Common in oceanic plankton at San Diego. Eupelagic in 

 warm temperate and tropical seas. 



Ceratium inclinatum, sp. no v. 



PL 2.5, figs. 16-21. 



"Ceratium tripos patentissiynum Ost. ", Karsteu (:06), p. 144, 

 Taf. 21, Figs. 23, 23a. Symmetry reversed in his figures. 



A small species of delicate habit, with narrow shoulders, slight 

 postindentation, and spreading antapicals distally incurved, with 

 contracted but still open tips, sometimes slightly inflated distally. 

 The antapical angle is usually 60°-80°. Differs from C. osten- 

 feldi in its more delicate habit, smaller size, lesser antapical angle, 

 and in the tips of the antapicals ; from C. macroceros in the tips, 

 narrower shoulders and more delicate habit. 



Length, 240-510/x,; transdiameter, 32-42^1* ; distance between 

 horns at girdle, 95-150/x ; at tips, 225-440/a. 



Abundant at times in the oceanic plankton off' San Diego. 



