386 MEMOIRS OF THE CARNEGIE MUSEUM 



Nat. Sc. Phil.); Town (Veek, Alleghany County, (H. A. Pilsbry coll., Acad. Nat- 

 8c. Phil.); Deer Park, Garrett County, (P. R. Uhler coll.). (See below under (\ 

 (Jioi/eihci^, footnote 2G.) 



PvEMAPvKS : 



Camharus Ixtrfnni 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 Penn.sylvania very uniform with regard to its morpholog- 

 ical characters (disregarding the variety robusias, 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 moi'e fioui-ishing 

 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 graduall}-- tapering in very young specimens (PI. XXXIX, Fig. }d and \e). 

 In older individuals it becomes broader, and is more suddenly constricted into a 

 longer or shorter acumen. Beyond this there is no rule. The most frequent shapes 

 are those figured on PI. XXXIX. Fig. l/> and Ir. Tiie one delineated in Fig. 1/is 

 exceptional. The other extreme is shown in Fig. \o, 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 nnn. and more in length are 

 not rare in Westmoreland, Allegheny, Elk, and Lawrence Counties. Specimens 

 between 70 and 80 nun. long have been found, in addition to the counties just 

 named, in Crawford, Venango, Potter, Jefferson, Butler, Armstrong, Washington, and 



