CAMBAKUS. 105 



of the outer row are developed. Third pair of legs hooked at base. First 

 pair of abdominal appendages long, deeply bifid, rami .slender, recurved, 

 parallel, inner ramus spoon-shaped at tip, outer ramus a little longer than 

 the inner, compressed laterally, tapering to a fine point at tip. 



Male, form II. — Lateral rostral spines a little more prominent, hand 

 smaller, hooks on third legs less strongly developed, first abdominal ap- 

 pendages thicker, bifid for only a short distance from the tip, rami laterally 

 compressed, blunt-pointed. 



Female — Rostrum as in the second form of the male, hand shorter and 

 wider. Annulus ventralis with well-marked transverse fossa. 



Measurements of a male, form I. — Length, 55 mm. Carapace, 25 mm. 

 Abdomen, 30 mm. Length of antenna?, 50 mm. Length of areola, 7 mm. 

 Breadth of areola, 2.5 mm. Length of chela, 21 mm. Breadth of chela, 

 9 nun. Length of movable linger, 12.5 mm. 



A female of the same size has the areola 3 mm. in width, 7 mm. in 

 length. 



Forty specimens, including both forms of the male and the female, were 

 collected by C. L. Herriek in Second Creek, Waterloo, Lauderdale Co., Ala.. 

 for the U. S. National Museum. The male appendages are very like those 

 of C. Mississippieims, the rami being longer and less strongly recurved than 

 in C. immunis. It is at once distinguished by its broad and short areola from 

 the other species in which the first abdominal appendages are formed after 

 the pattern of those of 0. immunis. The section of the carapace behind the 

 cervical groove is very short in this species, and the dense beard at base of 

 the external finger is very characteristic. In C compressus the areola, al- 

 though broad, is long, and the strong lateral compression of the body, differ- 

 ent form of the chela, etc., distinguish it from this species at a glance. 



45. Cambarus compressus. 



Plate V, fig. 6, Plate X. figs. 2, 2', 2 a. '! a/. 



Cambarui compressus, Faxon, Proc \mrr icad Aris and, Sci., \\ L27> 1884. 



Male, form I. — Rostrum narrow, excavated, curved downwards, with a 

 longitudinal median carina ; margins thickened, converging, with a line of 

 ciliated dots; acumen long, triangular, with acute Literal spines at base 

 which are obsolescent in the largest specimens. Cephalothorax strongly 

 compressed laterally. Post-orbital ridges armed with acute anterior spines. 



