Procambarus, a New Subgenus. 439 



Description of New Species. 



Cambarus (Procambarus) williamsoni spe<:. nov. 



Diag>iflsis. — Male sexual organs with the outer part blunt, the 

 inner slightly longer than the outer, narrower, but blunt ; in the first 

 form with a horny, procurved spine at the anterior margin, which is 

 represented by a blunt tubercle in the male of the second form. The 

 inner face of inner part slightly dilated and flattened, with two rows 

 of bristles diverging from a low oblique rib. Rostrum with distinct 

 lateral spines, acumen short ; its upper surface s-ubplane, without keel. 

 Sides of carapace granulated, with two spines on each side behind the 

 cervical groove. Areola very narrow, about half as long as the anterior 

 section of the carapace. Chelae loiig) subcylindrical, thickly scjuamoso- 

 granulated, the granulations larger on inner side of the carpojjodite 

 and hand, only in young specimens with an indistinct spine. Finger 

 shorter than the palm. Third pair of pereiopods with hooks in the 

 male. 



Description of Male of First Form. — Rostrum subplane, without 

 median keel, margins slightly elevated, convergent, with a distinct 

 lateral spine on each side a short distance from the tip. Acumen 

 short, triangular, with a fringe of stiff hairs. Postorbital ridges 

 divergent posteriorly, ending in a small spine anteriorly. Carapace 

 laterally compressed, suborbital angle rounded. Branchiostegal spine 

 distinct. Sides of carapace finely, but distinctly granulated ; two 

 sharp lateral spines on each side behind the crevical groove. Areola 

 about half as long as the anterior section of carapace, including the 

 rostrum, very narrow in the middle, with a single irregular row of 

 punctations. Abdomen as broad as, and slightly longer than, carapace ; 

 epimera rounded ; anterior section of telson with two spines on each 

 side. Anterior end of epistoma broadly triangular. Antenna with the 

 flagellum longer than the carapace, but shorter than the w-hole body. 

 Antennal scale broad, broadest in the middle. Chelce subcylindrical, 

 long, thickly beset with S(iuamiform granulations, which are largest 

 on the inner side. Fingers not gaping, shorter than palm, granulated, 

 and indistinctly longitudinally costate on upper side ; slightly pubes- 

 cent at the cutting edges, and with a few longer hairs. Carpopodite 

 without sulcus above, granulated like hand, granules largest on inner 

 side, but not spiniform (with exception of young specimens, where 

 there is a small spine at the distal end of inner margin). Meropodite 



