72 University of California Puhlications in Zoology. [Vol.8 



(1909c) with S. planktonis Steinhaus). While the form of the 

 body and degree of opacity is very similar, they differ radically 

 from one another. In 8. zetesios the heavy collarette serves to 

 distinguish at once between the two. The anterior fins are also 

 longer than the posterior fins, and originate at the ventral 

 ganglion in the latter species. 



According to Ritter-Zahony (1910), ^S^. elegans is identified 

 as a variety of ;S'. bipunctata. He recognizes two varieties of the 

 latter species, one of which he calls forma typica, and the other 

 forma arctica. While there is great similarity between them 

 there seems to be as much difference avS that between some other 

 species. In the first place I am unable to discover the least 

 trace of collarette in ^S". elegans, whereas in S. hi punctata that 

 structure, while not pronounced, is conspicuous. Then, the 

 muscles in S. bipunctata are weak, the body is nearly transparent, 

 the seizing jaws are not so numerous, and the general appear- 

 ance is decidedly contrasted to that of -S. elegans. The pro- 

 portional measurements are, however, annoyingly alike, and 

 altogether S. elegans resembles S. bipunctata more than any other 

 species. However, from the fact that the few differences men- 

 tioned are so distinctive and the general appearance so radically 

 different, it seems best to let S. elegans remain a valid species. 



Sag^tta tenuis Conant 



PI. 2, fig. 11. 

 Sagitta tenuis Conant (1896), p. 85. 



The receipt of three specimens of S. tenuis from the United 

 States National Museum made it possible to redescribe this 

 species. The specimens are labeled as cotypes obtained from 

 Jamaica, West Indies. They were all damaged, making it im- 

 possible to obtain as complete a description as desired. 



Characters 



Collarette present, but exceedingly small, as in S. bipunctata. Body 

 semi-opaque and firm (pi. 2, fig. 11). Muscles strong. Body widest at 

 about middle of its length. From this point it tapers gradually toward 

 head, and more rapidly toward tail. Neck nearly absent. Constriction 

 at tail-septum pronounced, as in S. enflata. 



Anterior fin beginning on a level with ventral ganglion. Shorter 

 than posterior fin. In length it varies from 12 to 13 per cent. 



Posterior fin longer than anterior fin with less than 50 per cent of its 

 length in front of tail-septum. It extends nearly, if not quite, to 



