ASTACID^E. 7 



ioiiii, B/«ii(I/ii(/n (after Ilarliui's doscriplion and figure), Wicgniaiiiu, 

 Mcvicanits, Cubotsk, Chikiisis (after M. Edwards's description), and 

 Om/mms (after Eandall's description and fignre). His materials were 

 few ; of A. pfUncidiis and ((ffinis he saw but one specimen, l)ut his de- 

 scriptions are largely comparative. The observation first made by Do 

 Haan, that the American species possess no gills at the base of the fifth 

 pair of legs, is repeated and verified in the other species described by 

 Erichson, and taken for the formation of a jiarticular subgenus, Ctoiikt- 

 rits. Erichson's monograph is still unrivalled, comprising all the species 

 of the whole world. Still, there is no certainty in the determination of 

 the species which he described, since so many similar species have been 

 more recently found. But it is jDOSsible to arrange them in my groups, 

 as Erichson has noted the number of hooked legs of the males. His 

 types are preserved in the Berlin Museum, and an examination of them 

 will prove, perhaps, that in the case of some species my determinations 

 are erroneous. 



1850. Mr. LcAvis R. Gibbes, in his work "On the Carcinol. Collect, in 

 the U. S.," 31, quoted Astacus Bartvmi, affinis, Blumlincjii, and pdlucidm. 

 But the localities given by him are doubtful, as I have seen very differ- 

 ent species presented by him, under the same name, to the Philadelphia 

 and the Cambridge Museums. 



18-54. The richness of the materials preserved at the Smithsonian 

 Institution in Washington, and chiefly collected by Professor S. F. Baird, 

 led Mr. Cli. Girard to examine them critically in "A Revision of the 

 North American A^faci, with 01)servations on their Habits and Geo- 

 graphical Distribution," Proc. Acad. Phil., VI. 87, and to characterize 

 them briefly, deferring to another opportunity more full descriptions, 

 accompanied by the necessary illustrations. Mr. Girard enumerates 

 twenty species, eleven of which are new. Two, C. Orc(/anus and 

 fossor, he had not seen. Professor Stimpson has kindly' communicated 

 to me the types of five of the eleven new species, namely, C. Clurkii, 

 propiiiqmis, mnntanus, rusticus, lonyiilus, and the types of two species 

 described before, namely, A. Bartonii and affinis. The Museum of the 

 Philadelphia Academy possesses also some species labelled with Mr. 

 Girard's names, which were kindly communicated to me by Professor 

 Leidy. I do not know whether these specimens are types, since some 

 are marked with a ? ; but as they are mostly from the localities quoted 

 by M. Girard, their identity is probable. These species are : C. Pmlci? 

 from the Potomac, C. rusiicus ?, C. vwnfmms ?, C. Dm/om ? from the Dis- 

 trict of Columlna, C. (icutissinms from Kemper County, Missouri, C. Blan- 

 dlngii from South Carolina, C. robustm from the Humber River at To- 

 ronto, C. propiwpnis? from Garrison Creek, Sackett's Harbor, C. moii- 

 iamts ? from the James River, Virginia. Also, of the twenty species 

 enumerated ]jy Mr. Ch. Girard I have certainly not seen his types of 



