ZOOLOGICAL SOCIETY BULLETIN. 



925 



«S3 



■V 



NORMAL AND PALE PHASES OF Cambarus limosus 

 The pale form is really much lighter than it appears in the cut, being nearly white. Photograph by R. C. Osburn. 



lower Hudson would gain considerable support. 

 There is a possibility that they may have been 

 distributed accidentally among water plants, 

 or that they have been purposely carried by 

 some one. At any rate there is no question but 

 that they have permanently adapted themselves 

 to the local waters. 



Our two local species of crayfishes may be 

 readily distinguished as follows: Cambarus limo- 

 sus has a strong spine on either side of the ros- 

 trum, or pointed projection between the eyes, 

 while C. bartoni lias no marginal spine on the 

 rostrum. In C. limosus there is a patch of spines 

 on either side of the carapace in the region of 

 the cervical, or neck, groove, while in C. bartoni 

 this region is only slightly granulated. There 

 are various other well-marked differences in 

 structure, form and color of the body, and espe- 

 cially in the appendages. 



A distinct color variation not hitherto 

 noticed in the species has appeared in C. limosus 

 from this vicinity. Faxon* and Ortmann (1. c, 

 pp. 355-6) have carefully described the colors 

 as usually found, which briefly stated are: Chief 

 color olivaceous with large blotches of dark 

 green ; under parts pale. Each segment of the 

 abdomen is marked above by paired brown 

 (burnt sienna) spots and there is a brown spot 

 on each side below the eye. The tips of the big 

 pincers are ferruginous and behind this is a ring 

 of dark green or nearly black. 



The color variety is not a case of albinism, for 

 the eyes appear to be as fully pigmented as in 

 the typical form, but there is an almost total 

 suppression of the normal bod}' coloration. The 

 ground color is almost white, but it is tinged 



* Revision of the Astacidae, Memoirs of the Museum 

 of Harvard College, vol. X, p. 88. 



