ANNELID GENUS CAMBARINCOLA — HOFFMAN 365 



nize, owing to the enormous dorsal jaw which dominates the entire 

 anterior half of the head. In no other known form in the famil}^ is 

 heterognathy carried to such an extreme. 



Additionally, the spermatheca offers very good specific characters, 

 particularh^ its length and pronounced median constriction which 

 are evident in every specimen examined. 



Presumably heterognatha is a highly modified member of the general 

 philadelphica-chirocephala stock, which began to evolve its characters 

 at a very remote time, or has been able to develop them more rapidly 

 than other species of the genus. 



DEMISSA SECTION 



A separate section seems necessary to reflect the status of 

 Cambarincola demissa, a very disjunct species which has little relation- 

 ship with other members of the genus. 



Judged from body shape, small head and jaws, and general appear- 

 ance, this species is perhaps one modified as a gill-inhabiting form, and 

 therefore especially liable to various structural concomittances of a 

 specialized habitat. Unfortunatel.y, we know nothing definite about 

 the preferred microhabitat of the species. 



Perhaps the most unusual feature of this animal is the marked 

 reduction in the size of the reproductive systems, indicated in outline 

 in the habit sketch of an entire worm (fig. 72). All of the normal 

 organs are present, with the fine structure characteristic of the genus, 

 but both spermiducal and prostate glands are very small proportion- 

 ately, and the latter — although histologically not differentiated — 

 terminates in a small clear bulb. The penial sheath of the bursa 

 is much smaller, in relation to the atrium, than in any other member 

 of the genus. 



DEMISSA GROUP 



A monotypic group with the characters of the section. The only 

 species is a moderately small, corpulent-looking worm, probably 

 branchiophilus, known only from extreme southwestern Virginia. 



Cambarincola demissa, new species 



Figures 72, 73 



Type specimens. — Holotype and four paratj^es, USNM 29948, from 

 Orconectes erichsonianus and 0. juvenilis collected in a tributary to the 

 Powell River at Big Stone Gap, Wise County, Virginia, by Horton H. 

 Hobbs, Jr., and C. W. Hart on June 17, 1950. 



Diagnosis. — A moderate-sized (2.8-3.2 mm. long) cuneate species 

 of Cambarincola, differing from all other members of the genus in the 

 exceptionally small sex organs, the prostate gland likewise differing 



