ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 389 
The shape of the carapace is similar to that of C. bartoni, but, in old specimens, 
appears slightly more depressed on account of the wider hepatic and branchial re- 
momes (alate 1s == ile ils) We eas Mod wo) Wet 
The rostrum (Plate XXXIX, Figs. 2a and 2b) is markedly different from the 
typical form, narrower, more tapering, and with a longer acumen; the upper sur- 
face is slightly concave. ‘The shape is rather variable. In young specimens of the 
typical C. bartoni the rostrum often approaches the form of C. bartoni robustus, but 
on the other hand young specimens of the latter have a narrower rostrum than the 
former. (Compare Plate XX XIX, Fig. leand 2b). In many cases the rostrum of the 
variety is not longer than in the typical form, but in others it surpasses it, reaching 
to the middle, or even almost to the end of the third joint of the peduncle of the 
antennula, or to the base or almost to the middle of the fifth joint of the peduncle 
of the antenna. 
Areola similar to that of the typical form, but with a larger number of rows of 
punctures (4-6), which is due to the punctures being more crowded, not only on 
the areola, but on the whole carapace. 
The carapace is often provided with small and sharp J/ateral spines; they are 
sometimes obsolete, or replaced by tubercles, or even entirely absent. 
Antennal scale generally slightly wider than in the typical form, and slightly 
longer. 
Antewnal flagellum not differing greatly from that of the typical form, and quite 
variable in length. There are a few cases where it reaches to the end of the telson, 
and even slightly beyond, thus surpassing any case known in C. barton. 
The first pereiopods (Plate XL, Fig. 3), display remarkable and important differ- 
ences from the typical form. The hand has nearly the same shape, but the fingers 
are less gaping, and meet all along their edges even in individuals of a considerable 
size (retention of juvenile character); it is only in very large specimens that they 
are distinctly gaping, but less so than in much smaller individuals of C. barton. 
The sculpture of the hand is much more strongly developed. The inner margin of 
the hand has a distinct and regular dowble row of tubercles. This double row is a 
very important character, and is noticeable in specimens from the size of about 30 
mm. upward. In very young individuals it is obsolete, and becomes more and 
more distinct with advancing age. Every specimen at hand, without excep- 
tion, possesses this character, when the chelee are normally developed ; but it must 
be mentioned that in regenerated chele, which are always recognizable by their 
shape, this double row is sometimes indistinct or irregular. Further, there is a tri- 
angular depression both on the upper and lower side of the hand at the base of the 
