380 CRAYFISHES. 



form of C. immunis from Illinois, C. immunis spinirostris differs in ha^'ing a 

 distinct spine or tooth on each side of the rostrum near the tip, more prominent 

 post-orbital and branchiostegian spines and a shorter posterior section of the 

 carapace in relation to the section in front of the cervical groove (the proportion 

 being 1:2 or even less in C. i. spinirostris) ; the claw, too is narrower, with 

 proportionally longer and slenderer fingers. 



In full-grown living specimens from Pontoosuc Lake (Plate 2, fig. 2) the 

 dominant colour of the carapace is a rich Vandyke brown shading into tawny olive 

 on the sides ; the cardiac area is conspicuously marked off by being a much lighter 

 colour, — tawny olive ; the abdomen is beautifully mottled above with darker 

 and lighter shades of tawny olive; the legs are olive-coloured. 



In the young, 27 mm. long, from the same locality (Plate 2, fig. 1), the brown 

 of the adult is replaced by an olive-green which pervades the whole dorsal side 

 of the creature and is delicately varied by mottling of olive-buff; the cardiac 

 area is of the latter hue and is continued backward, through the whole length of 

 the abdomen, as a broad median band; the appendages are delicate olive-green, 

 changing to a pinkish tint at the tips of the claws. 



C. i. spinirostris was first described from Obion County, Tennessee; it has 

 also been recorded from Omaha, Nebraska (Pearse), Shawnee County, Kansas 

 (Faxon), Douglas County, Kansas (Harris), Vigo County, Indiana (W. P. Hay), 

 Ottawa Co., Ohio (Pearse), and Long Point Creek, Canada (Pearse). As a mat- 

 ter of fact, specimens of C. immunis agreeing more or less closely with the form 

 which I described as var. spinirostris are to be found pretty much throughout 

 the range of the species. I have seen such among material collected in Ne- 

 braska, Kansas, Missouri, Michigan, Illinois, Indiana, Ohio, and New York. I 

 am therefore disposed to regard it as a variety rather than a true geographical 

 race or subspecies, although it is true that all of the Massachusetts specimens 

 . possess the characters of spinirostris. 



When Cambarus immunis was first discovered in Berkshire County, Mass., 

 it had been recorded from only one place (Oneida Lake, N. Y.) east of Lorain 

 County, Ohio, and in the State of Ohio it had been recorded from but three locali- 

 ties — Huron River at Huron, Erie County (Osburn and Williamson, 6th Ann. 

 Rept. Ohio State Acad., 1898, p. 11), Sandusky, Erie County (Faxon, Proc. U. S. 

 Nat. Mus., 1898, 20, p. 654), and Lake Erie, Lorain Co. (Osburn and Williamson, 

 I. c). I was therefore formerly inclined to think that its presence in Berkshire 

 County, Mass., was due to artificial introduction, like the Camharus affinis 

 in the ponds of Essex County, Mass. ; but I have now before me specimens from 



