KOFOID AND MICHENER: DINOFLAGELLATES. 295 



the elongated posterior spine whose length is 0.35 dorso-ventral diameter. 

 The fin is continued beyond this spine on the dorsal face, its surface smooth, 

 or irregularly reticulate, with a coarse, heavy, and (posteriorly) finely areo- 

 lated mesh. Surface of midbody coarsely and regularly pitted. Phaeosomes 

 spheroidal or ellipsoidal. 



Length, of midbody, 54 n, total, 115 m; dorso-ventral diameter, of midbody, 

 48 n, total 80 m; transdiameter, 36 n', phaeosomes, diameter of spheroidal 

 ones 3.5 n, ellipsoidal, 1 by 2.5 n- 



Sta. 4699. 



HlSTIONEIS COSTATA, Sp. D.OV. 



A small species resembling H. paulscni Kofoid (1907), pi. 15, fig. 94, but 

 differing from it in its stalked, rugose, oblique anterior collar, more rotund 

 body, and in the dorsal inclination of its posterior ribs. Body rotund, slightly 

 depressed anteriorly, without dorsal concavity, oblique ventrally at base of 

 inner collar which stands on a very slight eminence. Length of midbody 0.86 

 dorso-ventral diameter. Anterior collar stout, distinctly stalked, diameter 

 of neck nearly 0.25, of opening 0.91 dorso-ventral diameter of midbody. 

 Apex very oblique, heavily ribbed, with ends of ribs projecting beyond margin, 

 basally reticulate. Posterior collar a trifle wider than midbody, slightly 

 inflated, lower on right side, with simple dorsal, ventral, and horizontal ribs, 

 and low, hyaline distal frill, without other markings. Ventral fin, in indi- 

 vidual examined, low, reticulate, fission rib 0.33 dorso-ventral diameter in 

 length, standing at 45° from horizontal, posterior spine 0.6 dorso-ventral 

 diameter in length, directed obliquely dorso-posteriorly. Postmargin of fin 

 approaching horizontal, its whole surface unmarked. Surface of body coarsely 

 and deeply pitted, with scattered pores. 



Length, of midbody, 26 yu, total, 67 n; dorso-ventral diameter, of midbody, 

 30 n, total 40 m- 



Sta. 4604. 



HlSTIONEIS ELONGATA, Sp. IIOV. 



Resembles H. remora Stein but differs from his figure (1883), pi. 22, fig. 11, 

 decidedly in form of the midbody, and in details of collars and fins. Mid- 

 body elongated in postero-dorsal direction, its longer axis deflected posteriorly 

 about 40° from the horizontal, this axis 1.45 times the one at right angles to it. 

 Scarcely concave on antero-dorsal surface, slightly wider dorsally. Anterior 

 collar rises from rounded eminence, distinctly stalked, length of stalk 0.37 of 

 longer axis of midbody. Apex of funnel very asymmetrically sloped to right 

 and ventrally, distally ribbed, its opening 0.83 of longer axis of midbody. 

 Posterior collar as in H. remora but with distal hyaline frill and greater asym- 

 metry of horizontal bar. Ventral fin greatly elongated, ribbed on both 



