154 A- REVISION OF THE ASTACIDA. 
3. Astacus Trowbridgii.. 
Astacus Trowbridgii, Stimpson, Proc. Bost. Soc. Nat.. Hist., VI. 87, February, 1857.— Journ. Bost. Soc. 
Nat. Hist., VI. 493, April, 1857. 
Astacus Trowbridgii, J. G. Coover, Rep. U. 8. Pacific R. R. Expl., XII. Pt. IT. 388, 1860. 
Astacus Trowbridgii, Hacen, Ul. Cat. Mus. Comp. Zodl., No. I. p. 93, Pl. TIT. fig. 171, Pl. X., 1870. 
Astacus Trowbridgii, Faxon, Proc. Amer. Acad. Arts and Sci., XX. 152, 1884. 
Known Localities, — Oregon: Columbia River, near Astoria. Washington 
Territory: streams running into Shoalwater Bay (J. G. Cooper). 
There are types of A. Zrowbridgi in the collections of the U. 8. National 
Museum, the Peabody Museum of Yale College, the Boston Society of Natu- 
ral History, and the Museum of Comparative Zoology. There are also two 
specimens in the Academy of Natural Sciences of Philadelphia. One of the 
two female types in the collection of the Boston Society of Natural His- 
tory is figured by Hagen. The spine on the third segment of the antenna 
is commonly longer than represented by Hagen. 
In the larger specimens the posterior pair of spines on the carapace 
may be obsolete, while in other specimens these spines, although smaller 
than the anterior pair, are well developed, with acute, brown, horny tips. 
The dimensions of a large specimen as given by Stimpson are as fol- 
lows: — Leneth of body, 4.80 in.; breadth, 1.50 in. Length of rostrum, 
0.50 in.; acumen of rostrum, 0.18 in.; hand, 2.60 in.; breadth of hand, 1.15 in. 
The areola is two and one half times as long as it is broad. The dis- 
tance from the tip of the rostrum to the cervical groove is but a trifle more 
than twice the distance from the cervical groove to the posterior margin of 
the carapace. ‘The length of the acumen of the rostrum is equal to the dis- 
tance between the lateral spines of the rostrum. The tips of the first pair of 
abdominal appendages of the male are delicately membranous. 
Of the eleven specimens (six males, five females) which I have seen, 
nine are types collected by Lieut. Trowbridge in the Columbia River above 
Astoria, Oregon. Of the other two, in the Philadelphia Academy, one is 
labelled Columbia River, the other is without locality. According to Cooper, 
it is also found in the streams running into Shoalwater Bay, Washington Ter- 
ritory, to the north of Columbia River, and even in the brackish water of 
the bay. According to the same authority, its color, when fresh, is olive 
above; pale, tinted with red, below. 
A. Trowbridgi is closely related to A. deninsculus. Jt differs from it in the 
following particulars: the body is more obese; the cephalothorax is broader 
