156 A EE VISION OF THE ASTACID.E. 



groove, .0415 m. ; of rostrum, .0182 m. ; of abdomeii, .072 m. From near Hot Spring 

 Mountain. 



The second species is named Astacus chenoderma. " 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 cephalothorax of a third is asso- 

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

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

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

 preserved; its lower margin is unarmed, 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 the sides. As in A. stibgntndialis, there are two 

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

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

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



The third species, Astacus breviforce.ps, is " established primarily on 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 they 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 chelae is 

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

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

 sibly belong to it. It however differs in the finely vermiculate rugose character of its 

 surface. The rugae 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. subgrundialis 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. siibgrundialis. The succeeding pleura are 

 long, pointed, and slightly curved forward. "Some of the specimens indicate individuals 

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



According to Professor Cope, the beds in which these fossils were found 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 Otue 

 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. Gambclii. Cope himself 

 has pointed out the resemblance of the rostrum of A. subr/runduilis to that of A. Gam- 

 Idii, 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 Astacus. In the 

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

 fossil species more nearly resemble C. nigrescent. 



* Cope, ibid., p. 547. 



