240 



RITTER 



above. Both obscurely four-lobed, the lobes in preserved specimens 

 often imperceptible. Branchial tentacles, in the largest specimens at 

 hand, not much exceeding forty and not differing greatly in size. 



In a specimen 15 mm. in total length (one of the smallest at hand) 

 the tentacles are as follows : Twelve of good size and nearly equal, 

 twelve considerably smaller, alternating with these, and, alternating with 

 these twenty-four, the merest buds of as many more. From a com- 

 parison of this condition with that found in the largest individuals it 

 appears that, typically, new tentacles are added, first twelve and next 

 twenty-four, until the individual is well grown, and that then the 

 smaller, later tentacles continue to grow until all of the circle are in old 

 specimens, practically, of the same size. Dorsal tubercle prominent. 



Branchial sac with four folds on each side. Formula of internal 

 longitudinal vessels as follows : 



The frequent uncertaint}' as to \\hether vessels at the bases of the 

 folds should be counted as belonging to fold or space, and the frequent 

 change in direction of the vessels with reference to the folds at differ- 

 ent levels of the same sac, render it impossible to rely on this charac- 

 ter, except within rather wide limits. This remark applies especially 

 to small folds. 



Endostyle narrow and tortuous. Dorsal lamina a narrow, plain 

 membrane. 



Digestive tract. — Of the typical Styela type ; folds of the stomach 

 wall crowded, about thirty in number ; anus encircled by a fringe of 

 from ten to twenty blunt, irregular processes. 



Gonads, — Ovaries two cylindrical bodies on each side of the sac, 

 the ventral one on the left side suppressed in the region of the stomach. 

 Testis in the usual form of scattered nodules along the ovaries. Both 

 ova and sperm nearly, if not quite, ripe. 



This species is allied to S. mo?itereye?isis Dall, and S. greeleyi Rit- 

 ter, but the material now available for study furnishes no transitional 

 forms toward either. The most distinctive character is the propor- 

 tionate length of peduncle and body. In this respect the three species 



