350 MEMOIRS OF THE CARNEGIE MUSEUM 



These eight different forms are treated in the following pages, witli the addition 

 of one extralimital form, a variety of C. propinquas (C. prropnnqnu^i sdiiborni). The 

 recent and past ohservations made hy the writer, together with those collated frcjni 

 other sources, are presented as completely as possible in the succeeding pages, thus 

 giving a natural history of this group of animals, so far as found in the state of Penn- 

 sylvania. It has always been the aim of the writer to support his conclusions by 

 evidence secured within tlie state, but observations made oiitside of the state ai-e 

 sometimes introduced, where a gap was to be filled, or whei-e they were of special 



interest. 



III. MoRI'HOLOfiY AND ClIOROLOOY OF THE Pf.NNSYLVANIAN 8i'F,CTES. 



^■1. General Remarks. 



The crawfishes (as to the use of " ei'awfish " in preference to "crayfish" see infra, 

 VI) of the state of Pennsylvania belong to the genus (J(nnhara.'<- of Erichson (1846), 

 of the family Pufaiiiobiiehe Huxley, including the freshwater crawfishes of the north- 

 ern hemisphere. Faxon (1.S98) regards this as a subfamily, Amfaciurr, of the family 

 Astaciche, which also includes the subfomily, Pareisiaciiix of the soutlierii hemisphere, 

 now regarded as a family, rarastacidiv Huxley. There is some discussion as to the 

 proper name of the family, depending on the use of tlie generic name Astacvs Fab- 

 ricius, or of P(it(inu)I>i)(s Sainouelle, for the European crawfisbes. Tlie j)Osition ot 

 the writer was defined in 19(J2, {Proc. Amer. Philets. ibc. XLl, {). 276, footnote). 

 The question, however, has recently been finally settled by a discovery made by 

 Miss M. J. Rathbun {I'mc. Buil Si>r. Washington, XVII, HJOt, p. 170), but not in the 

 manner suggested by Miss Rathbun. The fact tliat the name Humarus was used 

 first by Weber [Nomenclatur EnUytnoloijicus, 1795), in ])lace of Astucus Fabricius, 1775, 

 makes Uom.anis a pure and simple synonym of Asfacus, and accoi'ding to the rule 

 " once a synonym, always a synonym," it remains a synonym. There is no reason 

 to make it " desirable," as Miss Rathbun expresses it, to set aside the rule in this case, 



The genus Caniharns, containing now about 70 species, has been variously sub- 

 divided : by Girard (1852) into three groups; by Hagen (1870) likewise into three 

 group.s, which, however, do not exactly correspond to those of Girard ; and Ijy Faxon 

 (1885'() into five groups. Recently tlie present writer has <livided the genus into 

 six subgenera, namely : Paracarnharns, Procarabarus, Cambarus, Cambnrellu-^, Fa.ro- 

 nius, BarUinuis. (See Prac. Atn. Phil. Soc. XLIV, 1905, p. 91. ef .'^cq. ; .l/(7(. Cam. 

 Mils. Ill, 1905. p. 437; and Pmr. Wn.shingfui, Ac<tiL Sricin'e, VI II, p. 1, 1906.) 



■^ Ericlison made this provisionally a subgenus, but e.xpre.sseil the opinion that it perhaps uould better rank as a 

 genus. Girard (1852) was the first to use Chmhiirus as a generic name. 



