1870.] ^^^ [Cope. 



ON THREE EXTINCT ASTACI FROM THE FRESH-WATER TER- 

 RITORY OF IDAHO. By Peop. E. D. Cope. 



{Bead before the American riiilosojjJdcal Society, Dec. IGtb, 1870.) 



ASTACUS SUBGRTJNDIALIS, Cope. 



This craw-fish is represented by four specimens, which include the ce- 

 phalothorax and region of the front, one of them including, also, the 

 post-abdomen to the end, with limbs ; three specimens with cheles, 

 one including a pair ; and one other specimen representing the post- 

 abdomen. 



The prominent characters of the species may be stated diagnostically 

 thus: Two tubercles on each side the front, the anterior si)iniform and 

 external to the basis of the lateral ridge of the ensiform process. The 

 latter narrow, medially grooved, acute, with five spinous points on each 

 side, and a terminal recurved spinelet. Surface of the cephalothorax 

 smooth or obsoletely wrinkled. Cheles nearly smooth, not granulate, 

 the superior edge sjiiniferous. Margins of the segments of postabdomen 

 produced into acuminate plates. 



I cannot determine the presence or absence of hooks on any of the 

 legs. The cheles are badly preserved in specimens of this species. 



The last segment of the cheles is furnished with a .longitudinal series 

 of strong reverted spines along the superior margin. They dimin- 

 ish in length proximally ; four or five are most prominent. In a speci- 

 men much smaller than the type, where the surface is preserved, it is 

 nearly smooth, and minutely striate. The longitudinal groove of the 

 penultimate joint is well marked ; this segment is not spiniferous. 



The antennal plates are large, and extend to nearly opposite the end 

 of the ensiform process at the front. The free abdominal segment is 

 punctate on its anterior half. The outer lamina of the postabdominal 

 segment is four times as wide as that of the others, with convex outline 

 to a point directed outwards and backwards. The laminse of the other 

 segments are acuminate triangular and transverse. 



The transverse siitnre of the external lamina of the flipper, marks the 

 posterior fourth of the whole length of the lamina. 



The lateral suture of the cephalothorax is deeply impressed. 



Four of the speciiuens represent individuals of large size : two are 

 smaller. The measurements are as follows : 



M 



Length to dorsal suture. No. 1 0.0415 



" of ensiform process only 0183 



Width " " at base 005 



Length postabdominal and flipper 072 



■' (width) free lamina 1st segment 013 



" outer lamina flipper 02 



" terminal segment flipper 005 



" femur, second pair abdominal legs 024 



" dorsum No. 2 from basal spine to suture 021 



