62 ASTACIDJE. 



rard's description of C. affinis being made from specimens from Reading, 

 and of C. Pealei from those of the Potomac, he was perhaps induced by 

 this difference (though he does not say so) to refer the individuals to 

 two species. The other differences given by him, namely, the longer 

 antennae, the broader area, the much less developed lateral spine of the 

 rostrum, have no decisive value. 



The Astacus limosus Rafinesque, Amer. Monthl. Mag., T. 2, p. 42, from 

 the muddy banks of the Delaware, is apparently the same species, as 

 quoted before by Mr. Girard. Rafinesque describes " a thorn of each 

 flank " and gives the extreme dimensions " three to nine inches." I 

 have seen specimens three inches long with oidy one thorn upon a 

 side, and I have no doubt about their identity. The largest specimen 

 seen by me is about five inches long. Nearly all younger specimens 

 (three inches long) are bearded at their articulations, as quoted by 

 Rafinesque ; the larger specimens show much less hair. The descrip- 

 tion of A. limosus was published in November, 1817, of A. affinis in De- 

 cember, 1817, one month later. But the description of A. affinis is so 

 perfect, that of A. limosus so imperfect, that it would be more suitable 

 to retain the name given by Mr. Thomas Say, although the other has 

 the priority. 



The identity of A affinis Erichs., Wiegm. Archiv, T. 12, p. 96, n. 15, is 

 probable. His description contains no different indication, but gives no 

 security. A. Bartonii Milne Edw., Hist. Crust., T. 2, p. 331, n. 2, is appar- 

 ently C. affinis. The typographical error in the quotation of the figures 

 by Mr. Harlan has misled Mr. Milne Edwards, as Erichson remarks. 

 The types of A. Bartonii Gibbes, in the Philadelphia Academy, are C. 

 affinis. 



Cat. No. 164, Havre de Grace, Md., Mr. T. R. Williams. Male Form I 

 Fern. Spec. 4. 



Cat. No. 180, Havre de Grace, Md., Mr. T. R. Williams. Male Form I. 

 Spec. 2. 



Cat. No. 163, New Jersey, Mr. Abry. Male. Fern., young. Spec. 3. 



Cat. No. 162, Schuylkill River, Pa., Mr. J. H. R. Male. Fern., young. 

 Spec. 6. 



Cat. No. 179, Niagara, N. Y., L. Agassiz. Male. Fern., young. 

 Spec. 12 * 



Cat. No. 177, Carlisle, Pa. Male. Fern., young. Spec. 2. 



Cat. No. 270, New York, Mr. Pike. Fern. Spec. 1. 



