134 A EEVISION OF THE ASTACID.E. 



3. Astacus Trowbridgiio 



Astacus Trowbridgii, STIMPSOJJ, Proc. Bost. Soc. Nat. Hist., VI. 87, February, 1S57. Joura. Bost. Soc. 



Nat. Hist,, VI. 493, April, 1857. 



Astacus Trowbridgii, J. G. COOPER, Rep. U. S. Pacific R. R. Expl., XII. Pt. II. 388, 1860. 

 Astacus Trowbridgii, HA.GEN, 111. Cat. Mus. Comp. Zool, No. III. p. 93, PI. III. fig. 171, PI. 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. Trowbridgii in the collections of the U. S. 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 : Length of body, 4.80 in. ; breadth, 1.30 in. Length of rostrum, 

 0.50 in. ; acumen of rostrum, 0.18 in. ; hand, 2.GO 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 Acadenry, 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. Trowbridgu is closely related to A. Icniitsculiis. It differs from it in the 

 following particulars : the body is more obese ; the cephalothorax is broader 



