Vol. 3] Kofoid. — Dinofagellata — New Species. 311 



salient girdle. It is but little larger than the hypotheca, which 

 has no antapical horns but only small acute points near the ven- 

 tral side of the antapical plates. There are no spines or fins as in 

 P. steini Jorg. The girdle is narrow and deeply impressed and 

 the transverse furrow forms an ascending right spiral with a 

 distal displacement equal to its width. The longitudinal furrow 

 is short and shallow, reaching only half way to the postmargin. 



There are three dorsal intercalary plates. The suture lines 

 are marked by exceedingly wide bands of intercalary striae. The 

 reticulated surface of the plates is correspondingly reduced. A 

 median row of thickenings on the striae marks the suture lines. 

 The plates are punctate with numerous minute pores. Plasma 

 dense, chromatophores brownish. 



Length, 88/x ; transdiameter, SSfx. 



Rare in oceanic plankton off San Diego in June and July. 



Peridinium rectum, sp. no v. 



PI. 32, figs. 48, 49. 

 A small species related to P. pedunculatum Schiitt, but having 

 a sharply differentiated, straight antapical horn of uniform 

 calibre. 



The body is ellipsoidal or less ovoidal than in P. peduncu- 

 latum and passes abruptly into a short straight apical horn, 

 0.1-0.2 of the transdiameter in length. The horn often flares a 

 little at the aperture but is not swollen as in P. pedunculatum. 

 The girdle is slightly postmedian, the transverse furrow is not 

 impressed, has thin hyaline lists and its distal end is displaced 

 anteriorly from 0.3 to 0.9 of its width. The two antapical spines 

 are finned, subequal, 0.3-0.5 of a transdiameter in length. Thecal 

 wall hyaline, structureless. Plasma rosy. 



Length, excluding horn and spines, 52/a; transdiameter, 43/a. 



Common in midsummer in oceanic plankton off San Diego. 



Amphidoma biconica, sp. no v. 



PI. 32, figs. 50-52. 



A medium sized biconieal species with wide girdle. 



Body biconieal, ends acuminate, epitheca and hypotheca ap- 

 proximately equal, ratio of their lengths 10:11. Epitheca a low 

 cone with its sides straight or slightly concave, equaling in length 



