156 A KEVISION OF THE ASTACID^. 



groove, .0415 ra. ; of rostrum, .0182 m. ; of abdomen, .072 iii. From near Hot Spring 

 Mountain. 



The second species is named Astacus chcnodcrma. " This species is represented by 

 the cheles of opposite sides of one individual, with which I associate with great proba- 

 bility one from the right side of a second. Part of a ceplialothorax of a third is asso- 

 ciated, but without conclusive evidence of identity, chiefly because of a near resemblance 

 in the sculpture." Tiie cheliB are long and slender, without spinous armature, but cov- 

 ered with thickly set granular tubercles. In the second specimen part of tlie carpus is 

 preserved ; its lower margin is uuarmed, while the outer face presents a series of short, 

 distantly placed spines. The surface of the carapace, as seen in the third specimen, is 

 delicately wrinkled by the confluent bases of fine pointed granules, which are directed for- 

 ward ; these become more scattered on tlie sides. As in A. suhjritiulUdis, there are two 

 pairs of post-orbital spines. Tlie areola is of moderate width. Length from rostrum to 

 cervical groove, .0235 m. Width of areola .25 incli from front, .007 m. Length of chela, 

 .045 m. Width of base of chela, .0173 m. From Catharine's Creek. 



The third s^qc\qs, Astacus brcviforccps, is "established primarily ou three cheles or 

 last segments of the fore limbs ; with these 1 have associated a cephalothorax of one, 

 and abdominal and postabdominal regions of three individuals. The only reason for such 

 reference of the latter is their superficial texture, in which tliey resemble the cheles, and 

 differ from the corresponding parts in the two other species." The chelse are short, thick, 

 the lower edge thin, the index rather short and conical ; the surface of the chel;e is 

 granular tuberculate, except on the convex faces, where it is finely vermiculate rugose. 

 " The cephalothorax associated is quite similar to that of A. suhgrundialis, and may pos- 

 sibly belong to it. Tt however differs in the finely vermiculate I'ugose character of its 

 surface. The rug;e are generally transverse on the back and sides." The upper surface 

 of the abbominal segments is marked with a delicate vermiculate rugosity, like that of 

 the cephalothorax. In A. suhgrundialis it is marked with impressed dots. The pleura 

 of the second abdominal somite are less than twice the width of the succeeding ones, 

 instead of being four times as wide, as in A. suhgrundialis. The succeeding pleura are 

 long, pointed, and slightly curved forward. " So:ue of the specimens indicate individuals 

 larger than those referred to A. suhgrundialis." From Catharine's Creek. 



According to Professor Cope, the beds in which these fossils were fouiul are of fresh- 

 water lacustrine origin, as determined by the fishes and mollusks found therein. As to 

 their age, there is "great probability of their being later than the Miocene, and nothing 

 to conflict with their determination as of Pliocene age." * 



Although nothing is known concerning the gills, or the presence or absence of hooks 

 on the legs, I am disposed to regard the fragments described by Cope as remains of true 

 Astaci, on account of certain superficial characters, such as the denticulate rostrum, the 

 post-orbital tubercles, the prominent acuminate abdominal pleura, etc. The only Astacus 

 known to inhabit the Territory of Idaho at the present day is A. Gamhelii. Cope himself 

 has pointed out the resemblance of the rostrum of A. suhgrundialis to that of A. Gativ- 

 hclii, and I have already shown (p. 131) that in the structure of the gills the last-named 

 .species approaches the primitive type more nearly than any other living Astacu.s. In the 

 elongated, acuminate alidominal pleura, and in the two pairs of post-orbital tubercles, the 

 fossil species more nearly resemble C. nigrcscens. 



* Cope, ibi<l., p. 547. 



