CAMBARUS. 55 



compressed from side to side, the carapace less granulate on the sides, more 

 sparsely punctate ; the branchial regions are more closely appressed, so that 

 they bulge upwards on each side of the areolar line, which thus comes to lie 

 in a depression in the median line of the back ; the metacarapace is longer 

 in proportion to the procarapace, the distance from the cervical groove to 

 the posterior margin of the carapace being equal to the distance from the 

 cervical groove forwards to the front end of the post-orbital ridge, whilst in 

 C. advena it falls considerably short of this ; the epistoma is truncate in front, 

 with a median spine ; in C. advena it is more rounded in front ; the antennal 

 scale is a little wider in front, with shorter apical spine ; the serrate crest 

 on the inner border of the hand is less prominent, and the lower face of the 

 hand is less clearly impressed at the base of this crest ; the carpus is less 

 spinulose within and below, and the line of teeth on the superior margin 

 of the meros is obsolescent, except the two distal ones ; the lateral margins of 

 the pleural of the abdominal somites are straighter ; the posterior segment of 

 the telson is shorter, and the spine at the end of the median rib of the inner 

 blade of the posterior pair of appendages is marginal, while in C. advena this 

 rib terminates in a spine some distance inside the margin. The first pair 

 of abdominal appendages are quite different, as will appear by comparison 

 of the figures on the first plate of Hagen's Monograph, bearing in mind that 

 the names of the two species are transposed on this plate. The distinctions 

 noted by Hagen, based on the presence or absence of spines on the lower side 

 of the first segment of the antennule and at the end of the cervical groove, 

 are not good, as the former is present in Le Conte's type of C. advena in this 

 Museum, and the latter is also apparent in most specimens of C. advena. The 

 statement of Hagen, that " in the larger specimens the hand is more sulcated 

 beneath at the inner margin, and the carpus moi-e spinulose," probably refers 

 to Le Conte's type of C. advena in the Philadelphia Academy. 



The female specimen in the same jar with the male just noticed differs 

 from the male in so many ways, that I doubt whether Hagen has properly 

 referred it to the same species. Its abdomen is not only very broad, but 

 longer than the cephalothorax, whilst in the male specimen it is consider- 

 ably shorter than the cephalothorax. The carapace is not strongly com- 

 pressed in the lateral direction, is more heavily punctate, the areola is 

 not impressed, the epistoma is sharply triangular, the antennal scale broader. 

 The tubercles of the internal border of the hand are less prominent, the 

 external border of the hand is marginate, instead of being rounded and 



