FRESH-WATER CRUSTACEA OF THE UNITED STATES. 653 



mon in most or all the tributaries of Lake Superior, and very likely of 

 many other of our nothern lakes and rivers.* The European species 

 alluded to below is said, by Dr. G. O. Sars, to be the food of a variety 

 of trout {Salino pmictatus) found among the higher mountains of Nor- 

 way, and our species probably serves a similar purpose in the waters 

 which it inhabits. 



This species is very closely allied to the Gammarus neglectus of G. O. 

 Sars,t which inhabits the lakes of Norway, and is apparently much 

 like it in habits. Our species differs from the European in some minor 

 details, and is undoubtedly entitled to be considered a distinct species. 



The name lacustris, which I first gave to this species, is pre-occupied as 

 a synonym of the European species just mentioned. 



Gammarus fasciatus Say. 



Journal Academy Nat. Sci. Philadelphia, vol. i, p. 374, 1817 ; (?)Bate, Catalogue 

 Aiuphipodous Crustacea British Museum, p. 210, pi. 37, fig. 6, 1862. 



Secondary flagellum of the antennulne as long as the second segment 

 of the peduncle, and composed of five or six segments. Antennte fur- 

 nished with many more, and much longer Tiairs than in the last species. 



First pair of legs in the male much as in the last species ; the palmary 

 margin of the propodus armed with the stout spine on the middle of 

 the inner side, and with two or three smaller spines near the tip of the 

 closed dactylus much as in that species, but there are no spines on pos- 

 terior margin proper. In the female, the propodus is only slightly nar- 

 rowed distally, and the palmary margin is not nearly so oblique as in 

 the male, or as in the same part of the female of the last species ; the 

 posterior margin furnished with several fascicles of hairs, but without 

 spines, except a cluster near the tip of the closed dactylus. Second 

 pair of legs in the male very much as in the last species, but there are 

 three or four spines on each side — usually four on the outside and three 

 on the inside — near the tip of the closed dactylus. In the female, the 

 second pair of legs are very much as in the female of the last species ; 

 but the carpus and propodus are not quite so elongated. 



Fourth and fifth segments of the abdomen slightly angulateddorsally 

 at the posterior margin, and each armed with three fascicles of spines 

 considerably larger than those in the last species, and the median fas- 

 cicle on each segment raised on a distinct protuberance. Sixth segment 

 with a median and lateral fascicles of spines. Outer rami of the poste- 

 rior caudal stylets with the terminal segment very narrow, styliform, 

 and without lateral hairs. Inner rami with usually one or two spines 



" Since the above was written, I have examined specimens of this species, collected 

 by Hayden's expedition in 1873, in Colorado, from a cool spring, Fire-Hole Basin ; and 

 very large specimens from an elevation of 9,000 feet, near Long's Peak. It was also 

 collected the same year by Dr. Cones, while on the Northern Boundary Commission. 



t Histoire Naturelle des Crustaces d'Eau Douce de Norvege, 1* livraison, p. 4G, pi. 

 4, 5 ; pi. 6, 6g. 1-20. 



