50 A REVISION OF THE ASTACTD-E. 



the United States Exploring Expedition West of the Hundredth Meridian in 

 pools east of the Canadian River. This locality, I presume is within the 

 limits of the State of Texas. 



17. Cambarus Mexicanus. 



; i richson, Aifh. Naturgesch., XII. Jahrg., I. 99, 1S4G. 



': Cambarus Azteeus, Safssuee, Rev. et Mag. de Zool., 2 e Ser., IX. 503, 1857- — Mem. Soc. Pkys. Hist. Nat. 

 Geneve, XIV. 460, PI. III. fig. 23, 1858. 



Hagen, 111. Cat. Mus. Comp. Zool., No. III. p. 84, 1870. (After Erielisou.) 

 Cambarus Mexicanus, Faxox, Proc. Anier. Acad. Arts and Sci., XX. 141, 1S84. 



Male. — Rostrum sub-plane, margins raised into crests gradually con- 

 verging until within a short distance of the tip. where the crests become 

 obsolete and the margins of the rostrum suddenly converge, without lateral 

 spines, to form the short-jwinted acumen. Post-orbital ridges parallel, obtuse 

 in front. Carapace laterally compressed, of nearly equal width throughout, 

 thickly punctate, sub-orbital angle rounded, cervical groove sinuate, no 

 lateral spine, branehiostegian spine small, blunt ; areola narrow, punctate. 

 Abdomen as long and broad as the eephalothorax, telson with three or four 

 small spines on each side, posterior segment short. Antennal scale broad, 

 broadest in the middle. Chela long, subcylindrical, thickly beset with squa- 

 mous ciliated granules; fingers about the same length as the hand, ciliate, 

 granulate, costate. Carpus hardly silicate above, covered with granules like 

 the hand ; no teeth on the inner margin. Meros granulate, outer surface 

 smooth except on the margins and distal end ; a biserial row of spines below. 

 Third pair of legs hooked. Sternum setose. First pair of abdominal ap- 

 pendages short, straight, a rectangular shoulder on the anterior margin near 

 the tip, external and internal parts in close apposition to their tips ; external 

 part furnished with a small, slender, procurved. horny spine ; internal part 

 flattened within, apex straight, scarcely separated from external part. 



Length, 51 mm. Carapace, 25 mm. Length of areola, 8 mm. ; width of 

 areola, 0.6 mm. 



The above description is drawn up from a specimen in the Academy 

 of Natural Sciences of Philadelphia, received from Mirador, Mexico, through 



Dr. SartonUS. The hooks on the third pair of legs are well developed, the 



firs! pair of abdominal appendages not articulated. 1 think there is no doubt 

 that this specimen is Erichson's 0. Mexicanus, the types of which could not 

 lie found in the Berlin Museum either by Dr. Ilagcn or Von .Martens. 



