324 PROCEEDINGS OF THE NATIONAL MUSEUM vol. ii4 



The outstanding characteristics of the Vitrea group he in (1) the 

 anisomorphic, essentiaUy homodontous smah jaws, and (2) the 

 strongly sigmoid shape assumed by the thick prostate and the long, 

 reflexed spermiducal gland. 



Whether actually two different species, or only subspecies, the two 

 forms of this group are interesting in exhibiting a certain amount of 

 geographic variation in the jaw size and proportions. As discussed 

 at length under the treatment of C. osceola, the size of the jaws relative 

 to head length varies in a general gradient from northwest to south 

 and thence northeast again. Furthermore, over most of the combined 

 range, the ventral jaw is subequal to the dorsal or slightly longer, 

 while in the northern segment of osceola the dorsal jaw becomes 

 distinctly longer than the ventral. 



The ranges of both forms coincide generally with lowland habitats, 

 a cu'cumstance which in many cases appears to enhance wide distribu- 

 tion by affording a sort of ecological continuity. 



The following key ^vill separate 100 percent of the specimens which 

 have been examined. The future student of this group is cautioned 

 that well-preserved specimens are essential for making accurate meas- 

 urements, and that material from the Gulf Coast States may be 

 expected to show some degree of intermediacj". 



Key to Species of the Vitrea Group 



1. Prostate gland larger in diameter, from 70-90 percent of the diameter of the 

 spermiducal gland et the base, averaging 82 percent; length of longest jaw 

 5-7 percent the length of the head (interior United States in the Mississippi 



River drainage Canibarincola vitrea Ellis 



Prostate gland smaller in diameter, from 50-70 percent of the diameter of the 

 spermiducal gland at the base, averaging 56 percent; length of longest jaw 

 7-9 percent of the head length (Atlantic and Gulf Coastal Plain region). 



Canibarincola osceola, new species 



Cambarincola vitrea Ellis 



Figures 25, 28, 29, 31 



Cambarincola vitrea Ellis, 1918, Pap. Michigan Acad. Arts Sci., vol. 37, p. 51; 

 1919, Proc. U.S. Nat. Mus., vol. 55, p. 249.— Goodnight, 1940, Illinois Biol. 

 Monogr., vol. 17, No. 3, p. 33; 1943, Journ. Parasitology, vol. 48, p. 188.— 

 Holt and Hoffman, 1959, Journ. Tennessee Acad. Sci., vol. 34, p. 103. 



Type specimen. — Holotype. USNM 17667, from Orconectes immunis 

 collected at Douglas Lake, Cheboygan County, Michigan, by Max M. 

 Ellis in July 1915. This specimen is mounted flattened dorsoventrally, 

 showing the jaws clearly; the reproductive systems are obscured, 

 however. 



Diagnosis. — A moderate-sized member of the genus, easily recog- 

 nized by the characters of the body form, jaws, and especially the 



