70 ASTACIDiE. 



ing compared many full-grown individuals, I find the following dif- 

 ferences : — 



Rostro non carinato, antice piano, vix angustiori; cretis basalibus 

 brevioribus ; lamina apice acutiori, margine externo non sinuato ; episto- 

 mate antice magis truncato ; chela latiori, planiori, margine interno in- 

 curvo, distincte biseriatim tuberculato, linea tuberculosa alia paululum 

 distante versus basin mediam digiti mobilis ; digitis brevioribus, latio- 

 ribus, externo incurvo, basi magis distantibus ; carpo subtus spinis anticis 

 distinctis ; pedibus abdominalibus margine postico medio dentato ; parte 

 interna lata recta, fere carinata, apice obtusa; postabdomine laminee 

 mediae parte apicali breviori. 



Forma II., pedibus abdominalibus basi articulatis, margine postico 

 non dentato ; partibus magis inflatis, externa cylindrica obtusa. 



Femina differt annulo apertura transversali antice bituberculata ; 

 tuberculo ventrali inter pedes secundos. 



Long. corp. 3.5 ; antenn. 2.5 ; ped. antic. 2.5. 



Patria : Genesee River, Rochester, N. Y. 



Vidi 30 specimina. 



This species is perhaps A. fossor Rafinesque, Amer. Monthl. Magaz., 

 T. II. p. 42. The description is very short, and contains nothing con- 

 tradictory, while the granular " gaping " toothed hand seems to desig- 

 nate this species rather than C. propinquus. 



" A. fossor. Antenna? as long as the body, rostrum short, one-toothed 

 on each side, a thorn behind the eyes ; three pairs of spiniferous feet, 

 hands of the first pair very large, granular-gaping-toothed, with a fur- 

 rowed and bispinous wrist. Obs. Vulgar name, burrowing lobster, — 

 communicated to me by Dr. Samuel L. Mitchell, — native of Virginia, 

 Pennsylvania, and New York ; size from four to six inches ; it burrows 

 in meadows and milldams, which it perforates and damages." 



The dimensions are greater than in the specimens before me. Among 

 the seven species known from New York, this species and C propinquus 

 are the only ones answering to Mr. Rafinesque's description. From 

 Pennsylvania I know only C. affinis and Bartonii, from Virginia only C. 

 Bartonii and C. obesus. 



I do not know whether C. obscurns burrows in dams ; should this pecu- 

 liarity be made out, the name proposed by Mr. Rafinesque must be 

 restored. 



Cat. No. 181, Genesee River, Rochester, N. Y., Mr. H. A. Ward. 

 Male. Fern. Spec. 12* 



Cat. No. 1840, Genesee River, Rochester, N. Y., Mr. H. A. Ward. 

 Male Form I. Fern. Spec. 12* 



Cat. No. 1841, Genesee River, Rochester, N. Y., Mr. H. A. Ward. 

 Male Form II. Spec. 3. 



