386 MEMOIRS OF THE CARNEGIE MUSEUM 
Nat. Se. Phil.); Town Creek, Alleghany County, (H. A. Pilsbry coll., Acad. Nat- 
Se. Phil.); Deer Park, Garrett County, (P. R. Uhler coll.). (See below under C. 
diogenes, footnote 26.) 
REMARKS: ; 
Cambarus bartoni is the crawfish of the small streams in Pennsylvania, and is 
exceedingly abundant all over the state. 
In spite of its wide distribution over parts considerably different in physical con- 
ditions, this species is in Pennsylvania very uniform with regard to its morpholog- 
ical characters (disregarding the variety robustus, to be discussed below). It is true 
that in the foregoing description many characters are pointed out which vary within 
certain limits; but these variations are not restricted to certain parts of the state, 
but occur everywhere. It is even hard to say of any character that it prevails in a 
certain region. In general there are indications that the species is more flourishing 
and also more variable in the western part of the state than in the eastern. ‘This 
observation, however, applies chiefly to characters which appear in very old speci- 
mens, as for instance, a stronger development of the tubercles on the inner margin 
of the hand and on the outer margin of the movable finger. Since the eastern form 
is much smaller, such characters, which are only occasionally present in very large 
specimens, are not found in specimens from the east, namely, strong sculpture of the 
hand and very thick margins on the rostrum. 
The most variable feature of this species is the rostrum. Generally it is narrower 
and more gradually tapering in very young specimens (Pl. XX XIX, Fig. 1d and le). 
In older individuals it becomes broader, and is more suddenly constricted into a 
longer or shorter acumen. Beyond this thereisno rule. The most frequent shapes 
are those figured on Pl. XX XIX, Fig. 1b and 1c. The one delineated in Fig. 1f is 
exceptional. The other extreme is shown in Fig. la, with margins practically par- 
allel, and a very sudden constriction into a comparatively short and broad acumen. 
Although this last shape is more frequent in the western part of the state, it is also 
found in the extreme eastern portions of the commonwealth. 
There is only one character in which regional variation may be observed, and 
this is the size of the body. As has been mentioned, in the eastern part of the state 
this species is considerably smaller than in the western, and the largest specimens 
are found west of the Chestnut Ridge. Individuals 80 mm. and more in length are 
not rare in Westmoreland, Allegheny, Elk, and Lawrence Counties. Specimens 
between 70 and 80 mm. long have been found, in addition to the counties just 
named, in Crawford, Venango, Potter, Jefferson, Butler, Armstrong, Washington, and 
