388 CRAYFISHES. 



pression running along the upper and lower faces of the immobile finger. In the 

 United States National Museum there are many specimens from West Fork 

 of Greenbrier River, W. Va. (No. 23,977, 23,978) and from Crane Creek, W. Va., 

 which are very nearly typical examples of C. b. rohuslus. They differ slightly, 

 it is true, from more northern sj^ecimens in having a little broader areola and less 

 pronounced impressions upon the immobile finger. In these regards they show 

 an approach to C. b. montanus, from which the form robustus is probably derived. 



Specimens collected at Wytheville, Wythe Co., Va. (U. S. N. M., No. 13,966, 

 M. C. Z., No. 3,838) which were referred to C. b. robustus by me in 1890 (Proc. 

 U. S. Nat. Mus., 12, 622) are in reality C. b. montanus. 



Examples from Fredericksburg, Spotsylvania Co., Va., were formerly referred 

 to C. robustus by Hagen in his Monograph, p. 80, and by myself in my Revision, 

 p. 61, 67, but they are not typical examples of C. robustus. These specimens 

 (M. C. Z., Nos. 3,615, 3,797) are in many ways like to C. acuminatus in the ros- 

 trum which is longer and more tapering than in i-obustus, in the relatively short 

 posterior section of the carapace, greater width of the areola, and the highly 

 developed spines at the base of the antennal scales, on the carpus, and on the 

 merus. The lateral spine of the carapace is distinctly developed on almost all 

 of the Fredericksbvu'g specimens. A similar form is found at Raleigh, N. C. 

 (U. S.N. M. No. 22,355). 



After eliminating the specimens which have been wrongly identified with 

 C. robustus, the distribution of the latter race, in its true form, is restricted, as 

 far as known, to the following regions: — Ontario: Toronto, Weston. Michi- 

 igan: Wayne, Washtenaw, Oakland, Sanilac, Huron, Oscoda, Crawford, Alcona 

 and Ionia Counties. Ohio: Knox, Lorain, Cuyahoga, and Ashtabula Counties. 

 New York: Chautauqua, Genesee, Allegany, Monroe, Wayne, Tomi^kins, 

 Oswego, Madison, Jefferson, St. Lawrence, Herldmer and Hamilton Counties. 

 Pennsylvania: Erie, Crawford, Warren, McKean, and Allegheny Counties (St. 

 Lawrence and Upper Ohio drainage). West Virginia: West Fork of Green- 

 brier River and Crane Creek. 



Cambarus bartonii robustus is a sombre-coloured crayfish in life (Plate 3), the 

 dominant color of the upper surface being a dusky olive tone, nearly uniform 

 and little relieved by the inconspicuously red-tipped fingers of the large claw. 

 The ambulatory appendages have a somewhat bluish cast, and the ventral 

 surface of the creature tends to a dull whitish tint. After the animal is placed 

 in alcohol, a large, bright red, quadrangular patch presently appears on the 

 branchiostegites behind the cervical groove, denoting that part of the shell which 



