350 PROCEEDINGS OF THE NATIONAL MUSEUM vol. ii4 



and Kentucky material, this organ is fairly robust and somewhat 

 longer than tlie bursa, while in specimens from Arkansas it is reduced 

 in overall size and is shorter than the bursal length. The prostate 

 remains unaffected over this range, so that in the southwest it becomes 

 porportionately longer and broader with respect to the spermiducal 

 gland. Presumably this variation is of at least potential systematic 

 interest, but whether it is evenly clinal in nature, or broken at some 

 intermediate area (such as tlie Mississippi Kiver) cannot be ascer- 

 tained on the basis of available material. Specimens from Illinois 

 are presently not at hand for study, and for tlie tmie being the matter 

 must rest at this point. 



There appears to be a similar east to west cline in jaw structure, 

 with the disparity in size becoming most distinct westward into 

 Kansas and Oklahoma. Kentucky material tentatively referred to 

 chirocephala can scarcely be distinguished from 'philadel/phica on the 

 basis of size of the jaws. 



Distribution. — Cambarincola chirocephala appears to be basically 

 autochthonous to the Ozark highlands, now reaching its greatest 

 abundance in northern Arkansas and Missouri. It extends, however, 

 eastward into Indiana and Kentucky where its range meets that of 

 philadelphica, with which it perhaps intergrades. Most of the 

 Indiana localities are in the Wabash River system; one, interestingly 

 enough, is in the Maumee River system which now drains northeast 

 into Lake Erie. The presence of chirocejihala in this drainage reflects 

 either fairly recent stream piracy in the region or transgression of the 

 low divides by crayfish — either possibility seeming equally likely. 

 It will be a matter of interest to establish additional records for the 

 species in northwestern Ohio and eastern Indiana. Goodnight 

 (1940, p. 38) has reported this species from a number of midwestern 

 localities as well as from some very unlikely stations in New York 

 and Virginia, and such extralimital records must be presumed to 

 have been based upon misidentifications. 



Material examined: 22 slides, from the following localities: 



Arkansas: benton county: Sugar Creek at crossing of U.S. Hy. 62, July 6, 

 1958, Holt (PCH 768). carroll county: South Fork of Dry Creek, 2.8 miles 

 east of Green Forest on U.S. Hy. 62, July 6, 1958, Holt (PCH 766). Critten- 

 den county: 14.6 miles south of Marked Tree on U.S. Hy. 63, July 5, 1958, 

 Holt (PCH 758). FULTON county: Salem, July 29, 1941, Horton H. Hobbs 

 (PCH 310). LOGAN county: West fork of Mill Creek, 4.4 miles west of Dela- 

 ware on Ark. Hy. 22, July 30, 1941, Hobbs (PCH 189). newton county: 

 Buffalo River, 14 miles south of Harrison on Ark. Hy. 7, July 29, 1941, Hobbs 

 (PCH 175). SHARP county: 3.2 miles southeast of Hardy, July 29, 1941, 

 Hobbs (PCH 176); about 9 miles west of Hardy, July 6, 1958, Holt (PCH 760). 



Indiana: allen county: St. Mary's River at Fort Wayne, Max M. Ellis 

 (USNM 17706). MONROE county: Bloomington, May 1915, Will Scott (USNM 



