ANNELID GENUS CAMBARINCOLA — HOFFMAN 321 



As now understood, the twelve species may be conveniently allo- 

 cated into five groups on the basis of characters taken in combination 

 and indicative of close afiinities. 



Key to Groups of the Philadelphica Section 



1. Prostate gland very long, much exceeding length of the spermiducal gland. 



(fig. 34), its terminal third slightly twisted or sinuate; verj^ large species. 



Ingens group (p. 333) 



Prostate gland never longer than the spermiducal gland and often much 



shorter; small to moderate-sized species 2 



2. Spermiducal gland with a very large lateral (posterior) deferent lobe (fig. 36) ; 



prostate terminating in a somewhat rudimentary bulb. 



ViRGINICA GROUP (p. 321) 



Spermiducal gland without a conspicuous posterior deferent lobe; prostate 

 terminating in a conspicuous bulb 3 



3. Spermiducal gland very long, its ental half refiexed closely upon the ectal 



half; in lateral aspect this gland together with the prostate assuming a 



distinctly sigmoid alshape Vitrea group (p.323) 



Spermiducal gland shorter, often strongly curved but never with the ental 

 half turned back against the ectal half 4 



4. Jaws strikingly dissimilar, the dorsal about eight times the bulk of the ventral; 



prostate gland about half as long as spermiducal gland or less; general size of 

 the male reproductive system reduced; body size small to moderate. 



Heterognatha group (p. 361) 



Jaws either identical in size and shape, or anisomorphic with the dorsal jaw 



slightly the larger; prostate at least half as long as the spermiducal gland; 



reproductive system normal in size for the genus; body size moderate to 



large Philadelphica group (p. 336) 



VIRGINICA GROUP 



This group is proposed to accommodate an interesting small worm, 

 herein described as new, which casts some light on the possible ante- 

 cedents of other members of the section. Cambarincola virginica, at 

 first sight, appears to be related to ouachita and to branchiophila 

 because of the large posterior deferent lobe of the spermiducal gland, 

 yet magnification reveals that the prostate is distinctly differentiated 

 and that the terminal bulb is present, in a rudimentary form. The 

 jaws of this species are quite similar to those of species in the Vitrea 

 group. 



I suggest that in this worm we have an approximation to the 

 ancestral form of the Philadelphica section shortly after the basic 

 dichotomy which has given rise to the three majo'- sections of the 

 genus. Tlie posterior deferent lobe is doubtless a primitive character 

 which lias become increasingly suppressed through the Philadelphica 

 section concomitant with the emphasized differentiation of the pros- 

 tate, and, also, the gradual reduction in bulk of the sex organs. 



