ORTMANN : THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 361 



Ischiopodife of tliird pereiopod hooked in the male, the hook in the male of the 

 first form being strong, subconical. 



Coxopodltes of posterior pereiopods without prominent crests or tubercles in the 

 male. 



First pleopods of male of the First fjrin (Plate XXXIX. 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 tlie two parts are completely 

 separated at the tips for a rather considerable distance (al)out one third of the 

 length from the inner Ijasal tubercle to the tip). Both parts are almost parallel, 

 only slightly convergent at the tips, which is due to a 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. Hoth 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 XXXIX, P^ig. Gh) are 

 articulated at the base when young, (only young specimens are at hand); both parts 

 are separated only foi- 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. 



Amiulus ventralis of female transversely rhombiform or ovate, rather Hat, 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 Hat. 



iSize. — Hagen gives 2.6 in. = 66 mm. as the maximum length for this species. The 

 largest individuals from the state of Pennsylvania observed by the writer, arc a 

 male (first form) from Albion, Erie County, 61.5 mm. long, and a female from the 

 same locality 69 nmi. long. I have seen, however, two larger males (first form) 

 from Lake Erie, off the shore of Lorain ( 'ounty, < )hio (Mus. Oberlin), one measuring 

 77 mm., tlic other 81 www. in Ici.gth. Nevertheless, this seems to be one of the 

 smaller species, for in the streams running to Lake Erie in IVnnsylvniiia a consider- 

 able number of intlividuals have been taken, none of whicii was longer than the 

 above mentioned specimens. 



Colors. — The colois of this species agree closely with tho.se of C ohscurus (which 

 see for further particulars). The following notes were taken from an adult female, 

 collected on the shore of Lake P]rie at Miles ( h-ove. 



