362 PROCEEDINGS OF THE NATIONAL MUSEUM vol. lu 



below. In many of its structural features, such as the disparate jaw 

 size and shape, small body, reduced size of the male reproductive 

 system, and particularly the shortened prostate gland, this species 

 shows a combination of evolutionary specialities which occm- only 

 singly in various other forms of the genus. 



Cambarincola heterognatha, new species 



Figures 69-71, 74 



Type specimens. — Holotj^pe and paratype, USNM 29947, from 

 Camharus sp. collected m a tributary to Big Wilson Creek, 4 miles 

 south of Mouth of Wilson on Va. Hy. 16, Grayson County, Virginia, 

 by Horton H. Hobbs, Jr., and C. W. Hart, June 14, 1950. Additional 

 para types indicated in the list of specimens examined. 



Diagnosis. — Immediately recognizable by the remarkably dis- 

 similar jaws alone. In addition, the male reproductive system is re- 

 duced in size and the prostate gland is less than half the length of the 

 spermiducal gland. 



Description. — A moderate-sized species, body length up to about 

 3.0 mm., somewhat fusiform m body outline, the greatest diameter at 

 segments vi and vii, the least at x. 



Head of normal size and proportions, about as broad as long, its 

 diameter less than that of segment i; peristomimn only a little flared, 

 without marginal lobes; head indistinctl}^ subdivided into two halves 

 by a slightly median constriction. Jaws very dissimilar in size, the 

 upper triangular with a large median projection and about eight times 

 the bulk of the lower (!) which is about equally quadrate in shape with 

 two small paramedian cusps. 



Body outline fusiform, segments vi and vii largest, each somite 

 divided by a distinct complete constriction, the prosomites the larger 

 of the two subsegments and not, or only slightly, elevated over the 

 level of the metasomites. 



Male reproductive system rather small, extendmg only halfwa}^ 

 up the side of segment vi. Bursa fusiform, widest near the middle, 

 about 1.5 times as long as broad, somewhat constricted at entry of 

 ejaculatory duct. Latter of moderate length and rather slender, less 

 than a third the bursa diameter. Spermiducal gland subreniform, 

 slightly broader entally, its diameter equal to or slightly greater than 

 that of biu-sa, the length a little greater. Prostate small and slender, 

 less than half as long as spermiducal gland, generally about a third as 

 long, the terminal bulb distinct. 



Spermatheca elongate and slender, abruptly constricted at the mid- 

 length, the ental half with a rounded tip or a slight ental process, the 

 organ extending dorsad nearly to the dorsal side of the coelomic cavity. 



