156 A REVISION OF THE ASTACID. 
groove, .0415 m.; of rostrum, .0182 m.; of abdomen, .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 chele are long and slender, without spinous armature, but cov- 
ered with thickly set granular tubercles. In the second spécimen 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 JA. subgrundialis, 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 breviforceps, is “established primarily on three cheles or 
last segments of the fore limbs; with these I 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 chelee are short, thick, 
the lower edge thin, the index rather short and conical; the surface of the chele is 
eranular 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 rue 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. subgrundialis. The succeeding pleura are 
long, pointed, and slightly curved forward. “Some of the specimens indicate individuals 
larger than those referred to A. subgrundiulis.” 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 true 
Astaci, on account of certain superficial characters, such as the denticulate rostrum, the 
post-orbital tubercles, the prominent acuminate abdominal pleura, ete. The only Astacus 
known to inhabit the Territory of Idaho at the present day is A. Gambelvi. Cope himself 
has pointed out the resemblance of the rostrum of A. subgrundialis to that of A. Gam- 
belt, 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. nigrescens. 
* Cope, ibid., p. 547. 
