ASTACIDiE. 77 



I have seen more than four hmuh-od speciiuons, 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 most 

 strongly tuberculated ; the auteuna3 are shorter than the aljdomen, 

 though in one male (the largest seen by me) they arc 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 ^1. Baiion'd 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 (N. 

 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. affiuis M. Edwards seems 

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

 affinis. 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 Burtoidi, but he quotes the works above-mentioned. Girard cites 

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

 and this is po.ssibly true of very large specimens. 



Girard describes (1. c. p. 90, n. 13) A. piisillus 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. pitsilli(s does not differ from A. Bartonii, 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 

 C. ohcms it is entirely denticulated. Cilia evidently occur on the second 

 pair of leg,s, 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, with the 

 eyes well developed, and a female from Georgia. 



In the largest male from Ohio the antennae 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. Bartonii Er., and communicated by Professor Stimp.son. 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 Caintjanis montanus Girard, 1. c. p. 88, male type 

 from Greenbrier River, Virginia, commmiicated by Professor Stimp- 



