I905-] 



ORTMANN — AFFINITIES OF CAMBARUS. 107 



C. chapalanus and montezumce still remain in the original home of 

 the genus, although they have changed a good deal, C. shufeldti 

 seems to be an early emigrant, which, however, has not much 

 changed. Further investigations in this subgenus are much needed. 



Subgenus: Faxonius (Type: C. limosus)} 



This subgenus corresponds to Faxon's fourth group, with the 

 addition of C. pellucidus. As regards the latter species, which 

 Faxon places with his first group, apparently chiefly on account of 

 the presence of hooks on the third and fourth pereiopods in the 

 male, it is easy to see that the sexual organs do not agree with the 

 blandingi-type. Faxon himself says (1885, p. 42), that they are 

 very simple, and generally admits that this species unites characters 

 of different groups. Looking at the figures of the sexual organs 

 given by Hagen (111. Cat. Mus. Harvard, 3, 1870, pi. 1, f. 68-71), 

 and Hay {P. U. S. Mus., 16, 1893, pi. 45, f. 11-14), I fail to 

 see any similarity to any of the species of the subgenus Cambarus, 

 but their shape approaches rather closely that of some species of 

 Faxon's fourth group, namely : C. limosus, indianansis and sloanei. 

 Indeed, in C. pellucidus this organ is different from any one of 

 these, but it agrees with them in the more or less straight and 

 simple form, with the outer and inner parts separated at the tips 

 for a short distance ; there is also no trace of a terminal truncation. 

 The rostrum and the chelae are rather primitive in C. pellucidus, 

 while carapace and areola are peculiar, which is possibly a char- 

 acter due to the subterranean life (see Faxon). 



If we place C. pellucidus with the species of the fourth group 

 named above, it loses its isolated position also with reference to 

 the geographical distribution: it is found in a region (Kentucky 

 and southern Indiana), where at least two of the above species are 

 also found : C. indianansis and sloanei. 



I think, that C. pellucidus is a rather primitive form, connecting 

 the subgenus Faxonius with the more primitive forms of Cambarus 



1 Astacus limosus of Rafinesque has been considered by all authors (Girard, 

 Hagen, Faxon) as very probably identical with A. ajfinis of Say. Although 

 Rafinesque' s description is very poor, the locality given (" muddy banks of the 

 Delaware near Philadelphia") renders it absolutely certain that C. affinis was 

 intended. There is no other species on the banks of the Delaware but this, and it 

 is so abundant there, that it even attracts the attention of the casual observer. 

 Thus I do not see why the older name of Rafinesque should not be restored. 



PROC. AMER. PHII.OS. SOC. XLIV. iSo. H. PRINTED JULY 28, I905. 



