Vol. 3] Kofoid.~Dinoflagellata—New Species. 301 



tween the longitudinal furrow and the distal end of the trans- 

 verse one (PI. 22, fig-. 2). The longitudinal furrow extends from 

 the dorsal half of the epitheca to the antapex, and is a narrow 

 deep channel on the epitheca but widens out on the hypotheca. 



The surface is covered by a thin hyaline membrane noted by 

 Stein ( '83) but omitted in the g'eneric diagnosis of Schiitt ( '96). 

 Nucleus spheroidal, in the middle of the hypotheca, with monili- 

 form chromatin reticulum, and two polar centrosomes (!) sunk 

 into its substance. A pyriform vacuole lies near the flagellar 

 pore and small angular yellowish chromatophores are scattered 

 about the amyloid body. Plasma dense and coarsely granular. 



Length, 68yu, ; transdiameter, Sd/j. ; dorso-ventral, 55/x, ; nucleus, 

 15/x. 



Taken in a vertical haul from 90 fathoms off San Diego in 

 June. 



This is the second pelagic species of this genus, the other being 

 A. aculeatum Daday ('88) from Naples. The other species of 

 the genus are from fresh (A. lacustre) or brackish (A. opercu- 

 latuni) water. 



Heterocapsa pacifica, sp. no v. 



PI. 22, figs. 4, 5. 



A very minute species with prominent asymmetrical spine, 

 resembling H. triquetra but less elongated. 



Body oval, dorso-ventrally compressed, the length, excluding 

 spine, 1.3 times the transdiameter and 2.1 times the dorso-ventral 

 one. Epitheca exceeds the hypotheca, its altitude 0.75 of the 

 basal transdiameter, its sides slightly convex. Apical pore pres- 

 ent. Hypotheca less than 0.5 of the transdiameter in height, 

 slightly asymmetrical, the right side more convex than the left, 

 continued posteriorly in a stout acuminate antapical spine a little 

 to the left of the axis. Its base merges gradually into the outline 

 of the hypotheca and its length is 0.3 of a transdiameter. There 

 is a slight elevation on the right side suggestive of a second rudi- 

 mentary antapical spine. 



The girdle is postmedian ; the transverse furrow is impressed, 

 without lists and forms a descending right spiral displaced dis- 

 tally nearly its own width. The longitudinal furrow is faint and 



