I LMBARUS. 75 



There elapsed some three or four minutes between each appearance; but 



every time it came, it brought a ball of clay and deposited it in the manner 

 1 have described. About two Qfths of the balls were not placed with suffi- 

 cient care, and rolled down the outside of the chimney." 



Dr. Abbott believes that the closing of the orifice of a chimney is merely 

 the result of the accidental falling in of pellets from the rim, loosened 

 perhaps by atmospheric moisture. In some localities where the burrowing 

 crayfish abounds, there is a weather proverb to the effect that, when the 

 crayfish closes the opening of his chimney in dry weather, there will be a 

 rainfall within twenty-four hours. 



It is difficult to imagine the object of this crayfish in building these 

 elaborate. subterranean abodes. Further observations on the method of tun- 

 nelling, on the winter habits of the animal, and on its mode of life during 

 the breeding season, are much needed. 



The mud chimneys built by C. Diogenes were observed and figured long 

 ago by Audubon (Birds of America, Plates ■I'l'l, 386 ; 8vo eel., Plates 360, 

 370), who describes the ingenious device whereby the White Ibis draws the 

 crayfish from its retreat (Vol. VI. p. 57). 



In life C. Diogenes is olive-colored, reddish on the margins of the rostrum, 

 the post-orbital ridges, and the margins of the abdominal somites ; chela? 

 cream-colored within, lingers reddish. 



The largest specimen which 1 have seen from the East measures 84 nun. 

 from the tip of the rostrum to the end of the telson. Specimens received 

 from Illinois measure 111 mm. in length. 



According to Forbes and Bundy, C Diogenes is one of the commonest 

 species in Illinois and Wisconsin. 



27. Cambarus Nebrascensis. 



r, Girard, Proc. Lead. Nat Sci. Pkila., VI. 91, 1852. 



Cambarus Nebrascensis, Bagen, 111 Cat. SIus. C p. Zool., No. Ill p. 83, 1870. (After Girard.) 



is, Faxon, Proc. A.mer. Acad. A.rts and Sci . \\. 1 15, l ss l. (After Girard, No de- 

 scription.) 



"Rostrum intermediate in form between that of C. robustus and C. Dio- 

 genes. Dorsal lines of suture of the carapace in close contiguity. Large 

 claw nearly conical, giving to the specie- a very peculiar aspect. 



"Locality. — Fort Pierre (Nebrasl i); collected in L850 by Thaddeus Cul- 

 bertson." Girard. 



