ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 361 
Ischiopodite of third pereiopod hooked in the male, the hook in the male of the 
first form being strong, subconical. 
Coxopodites of posterior pereiopods without prominent crests or tubercles in the 
male. 
First pleopods of male of the first form (Plate XX XIX, Fig. 6a) slender, but 
rather short, hardly reaching beyond the middle of the coxopodites of the third 
pereiopods. They are not articulated at the base, and the two parts are completely 
separated at the tips for a rather considerable distance (about one third of the 
length from the inner basal tubercle to the tip). Both parts are almost parallel, 
only slightly convergent at the tips, which is due toa very slight curve of the outer 
part. Outer part gradually tapering from base to tip, horny. Inner part soft, of 
about the same shape as the outer, and of the same length, gradually tapering to 
an acute tip. Both parts are slightly twisted, so that the tip of the outer is directly 
anterior to that of the inner. Anterior margin of this organ without shoulder 
shortly below the point of separation of the two parts; sometimes, indeed, there is 
a slight notch, but never a sharp shoulder. 
In the male of the second form, the first pleopods (Plate XX XIX, Fig. 65) are 
articulated at the base when young, (only young specimens are at hand); both parts 
are separated only for a short distance, and are soft; the outer one is rather 
blunt, while the inner one tapers to a point. No notch or shoulder on anterior 
margin. 
Annulus ventralis of female transversely rhombiform or ovate, rather flat, very 
slightly depressed in the middle, with an S-shaped longitudinal fissure. No tuber- 
cles on anterior part. In young females, the median depression is very indistinct, 
and the annulus is almost completely flat. 
Size. — Hagen gives 2.6 in. = 65 mm. as the maximum length for this species. The 
largest individuals from the state of Pennsylvania observed by the writer, are a 
male (first form) from Albion, Erie County, 61.5 mm. long, and a female from the 
same locality 69 mm. long. I have seen, however, two larger males (first form) 
from Lake Erie, off the shore of Lorain County, Ohio (Mus. Oberlin), one measuring 
77 mm., the other 81 mm. in length. Nevertheless, this seems to be one of the 
smaller species, for in the streams running to Lake Erie in Pennsylvania a consider- 
able number of individuals have been taken, none of which was longer than the 
above mentioned specimens. 
Colors. —'The colors of this species agree closely with those of C. obsewrus (which 
see for further particulars). The following notes were taken from an adult female, 
collected on the shore of Lake Erie at Miles Grove. 
