astacid^:. 77 



I have seen more than four hundred specimens, both very young and 

 very old. The shape of the rostrum is variable, sometimes broader and 

 quadrangular ; the sculpture is different, the oldest individuals are must 

 strongly tuberculated ; the antenna? are shorter than the abdomen, 

 though in one male (the largest seen by me) they are a little longer 

 than the abdomen. The hands are variable in form, often very broad, 

 and the fingers much separated at the base ; the abdominal legs in the 

 second form are often not articulated. 



It is possible that A Bartomi Fabr. belongs to this species ; the de- 

 scription contains no contradictory characters. The description by 

 Bosc is too short, and his figure too imperfect to afford any help. The 

 species of Say. Harlan. Erichson, are apparently identical. DeKay's ( X. 

 Y. Fauna, T. 6, p. 20, T. 8, fig. 25) description is very brief and the fig- 

 ure poor, still I think the species the same. A. affirms M. Edwards seems 

 to be the same (Crust. II. p. 332, n. 3). A. Bartomi. M, Edwards is C 

 affims. I do not know whether M. Edwards has seen the type of Bosc. 



Girard gives (Proc. Acad. Philad., No. 8, T. 6, p. 88) no description 

 of his Bartoim, but he quotes the works above-mentioned. Girard cites 

 as identical A. ciliaris Rafinesque (Amer. Month. Mag. II. No. 3, p. 42), 

 and this is possibly true of very large specimens. 



Girard describes (1. c. p. 90, n. 13) A. pusillus Rafin. The description 

 by Rafinesque (1. c. No. 4, p. 42) is too short, '-the rostrum oval acute," 

 and - wrist smooth," being the only important characters given. The 

 comparative description by Girard is not sufficient, though the Cam- 

 bridge Museum possesses one female from Lake Champlain by Professor 

 Baird, possibly the A. pusillus Rafinesque. 



I suppose that C. pusillus does not differ from A. Bartomi, because 

 the examples from the North, Lake Superior, and other localities are 

 always very small. The external lamina of the postabdomen has the 

 inner third of the apical margin of the basal part not denticulated ; in 

 ('. obesus it is entirely denticulated. Cilia evidently occur on the second 

 pair of legs, and justify the name given by Rafinesque. The basal in- 

 ner angle of the hand is nearly rectangular. 



I have seen a female from the Mammoth Cave, Kentucky, Avith the 

 eyes well developed, and a female from Georgia. 



In the largest male from Ohio the antenna? are longer than the body. 

 — a character given for C. montanus Girard, — but the areola is not 

 broader. 



I have compared a female type from Berwick, Pennsylvania, labelled 

 C. Bartomi Er., and communicated by Professor Stimpson. The speci- 

 men is from the locality mentioned by Mr. Girard and identical with 

 the specimens described by me from Schuylkill River. 



I have also compared Gamharus montanus Girard, 1. c. p. 88, male type 

 from Greenbrier River, Virginia, communicated by Professor Stimp- 



