ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 409 
of the western form is generally shorter. While in the eastern form it is at least one 
and one-half times as long as the palm, in the western form this relation is the 
maximum, and is due to a proportionally heavier and stronger development of the 
palm as compared with the fingers. (This does not hold good for regenerated 
chelz, in which the dactylopodite always is considerably longer in proportion to 
the palm.) 
The tubercles of the cutting edge of the dactylopodite are slightly different in 
both forms. In the eastern the third or fourth js generally much larger, and, just 
before it, there is a gap, as if one tubercle were suppressed. This produces a distinct 
excision at the base of the finger, which is always more or less marked, even in 
rather young individuals, so that the fingers always appear gaping at the base (PI. 
XL, Fig. 6). In the western form the fourth or fifth tubercle is larger than the 
rest, but there is no distinct gap anterior to it, the three or four proximal tubercles 
being rather equidistant. They decrease slightly in size from the first to the fourth, 
so that a slight emargination is indicated. But this emargination and the large 
tubercle following it are well distinguishable only in larger individuals ; in younger 
specimens they are rather indistinct, or entirely wanting, so that the basal gap is 
absent, and the fingers are in contact all along their edges. 
The differences in the relation of dactylopodite to palm, and in the tubercles of 
the dactylopodite, give to the whole chela of the western form a different aspect, 
the hand appearing rather more massive with shorter fingers. (See Pl. XL, Figs. 
6 and 7.) 
8. The colors in western specimens are more vivid, and with more contrast. 
Eastern specimens are more uniformly russet or olive-green, with no oil-green at the 
base of the fingers, while the latter tint is very characteristic of thé western form, at 
least in specimens of a certain size. Old western specimens, when fresh, are rather 
brilliantly colored. 
I think Iam able to recognize and to distinguish eastern and western speci- 
mens, chiefly by the help of the characters of the chele, if the latter are normally 
developed ; but I do not know whether it would be advisable to distinguish both 
forms by varietal names. The latter may be necessary in future, when the forms of 
C. diogenes from the regions west of Pennsylvania have been more closely studied. 
I think I am able to see certain differences in the western specimens in our collec- 
tions, but the material is too poor to be sure of it. 
No remarkable freaks or malformations have been observed in this species, with 
the exception of a few color variations. They are the following : 
1. In Fern Hollow, Pittsburgh, a specimen was found in astagnant pool, 6 to 
