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. robustus. They differ slightly, 
it is true, from more northern specimens 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 (Proce. 
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 robustus, 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 Fredericksburg 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:— Ontarto: Toronto, Weston. Mu1cHt- 
IGAN: Wayne, Washtenaw, Oakland, Sanilac, Huron, Oscoda, Crawford, Alcona 
and Ionia Counties. On1o: Knox, Lorain, Cuyahoga, and Ashtabula Counties. 
New York: Chautauqua, Genesee, Allegany, Monroe, Wayne, Tompkins, 
Oswego, Madison, Jefferson, St. Lawrence, Herkimer and Hamilton Counties. 
PENNSYLVANIA: Erie, Crawford, Warren, McKean, and Allegheny Counties (St. 
Lawrence and Upper Ohio drainage). Wurst 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 
