CAMBAEUS. 107 



A small species, with first aljilomiiial appendages of the male similar to 

 those of C. immuim. It is readily distinguished from all the other species 

 with similar male appendages by the lateral compression of the cephalo- 

 thorax, form of the chela, etc. 



46. Cambarus medius. 



Plate III. fis. 4, Plate IX. flgs. 4, 4'. 

 Cambarus medius, Faxox, Pruc. Amer. Ac;id. Arts and Sei., XX. 121, 1884. 



Male, form I. — Rostrum of moderate length, excavated, slightly cari- 

 nated at the tip ; margins thickened, converging, sinuated near the tip to 

 form the short triangular acumen; no lateral spines. Post-orbital ridges 

 depressed, snlcated on external face, subacute anteriorly. Carapace sub- 

 cylindrical, somewhat flattened above, punctate, granulated on the sides; 

 cervical groove sinuate, no lateral or branehiostegian spine; sub-orbital an- 

 gle rounded ; areola long (much more than half as long as the distance from 

 the cervical groove to the tip of the rostrum), of moderate width, punctate, 

 widening posteriorly. Abdomen as long as the cephalothorax ; telson 

 rounded behind, basal segment bisjiinous on each side of the posterior bor- 

 der. Basal segment of antennule with an interior median spine. Second 

 and third segments of antennoe not spiniferous (flagellum of antenna3 broken 

 off in the specimen examined, probably much shorter than the body). An- 

 tennal scale short, of moderate width, terminating in a short, acute spine. 

 Anterior process of epistoma triangular, apex pointed, sides convex. Third 

 maxillipeds bearded within. Chelipeds of moderate length, stout; chela 

 broad, inflated, coarsely punctate above and below, external margin rounded ; 

 internal margin of liand with a double row of obsolescent tubercles ; fingers 

 stout, gaping at base, costate, heavily dotted-lined, internal margins fur- 

 nished with rounded tubercles. Carpus sparsely punctate, armed with a 

 moderate median and a smaller basal internal spine; below, there are no 

 spines developed. Meros furnished with two nearly obsolete obliquely 

 placed tubercles near the distal extremity of superior border, and with a 

 double row of tubercles below. Second pair of legs provided with long cilia 

 towards their distal extremity. Third segment of third pair of legs hooked. 

 First pair of abdominal legs long (reaching to base of chelipeds), deeply bifid, 

 rami slender, straiglit. the outer one a little recurved at the tip, aciculate, 

 the inner one slightly dilated near the tip, blunt pointed ; a projecting augle 

 or shoulder at base of rami on anterior margin. 



