104 University of California Puhlications. [Zoology 



rior process. On the neck the pits gradually widen to a coarse 

 reticulum 2-4 meshes wide on each valve. 



The nucleus is very small (in some cases observed) and is 

 located posteriorly. There are a few irregular chromatophores, 

 or numerous ellipsoidal ones gathered along the ventral margin. 



This species, in the individuals thus far observed, is quite 

 uniform in dimensions and proportions, except in the diameter 

 of the three processes from the midbody. These vary consider- 

 ably in thickness but less in length, thus giving to the organism 

 different degrees of robustness with little change in the other 

 dimensions than the diameter of the processes. 



Taken in plankton from 180-30 fathoms to surface off San 

 Diego, but always sparingly. 



Dimensions: Length, 113-145 fi; distance between knees of 

 antapicals, 83-115 /x ; distance between tips of antapicals, 70-106 

 fx : distance from apex to middle of posterior margin of midbody, 

 77-97 /,i: length of neck, 25-28^: dorso-ventral diameter of mid- 

 body, 33-40 IX. 



This is the type species. 



Triposolenia depressa sp. no v. 



PI. 16, figs. 3, 4. 



A small species with midbody elliptical in lateral view, convex 

 margins, and antapicals of T. hicornis type with truncated spin- 

 ulate tips. 



This is the smallest of the known species of the genus and is 

 characterized by the foreshortening of the antero-posterior axis 

 of the midbody which gives to it an ellipsoidal form with its 

 major axis in the dorso-ventral position. The three margins are 

 all strongly convex and the antero-ventral is somewhat shorter 

 than the others. The antero-posterior axis is 0.25 of the total 

 length and 0.8 of the dorso-ventral axis of the midbody. The 

 anterior process is very short and oblique, with well marked 

 cytopharyngeal swelling. Its length is about 0.5 of the antero- 

 posterior axis of the midbody. The neck is short and straight or 

 very slightly curved dorsally toAvard the head, and obliquely de- 

 flected dorsally 35° from the axis of the anterior process. Its 



