42 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxii. 



not quite so long as the first segment of the outer ramus, armed with a 

 few spines on the inner margin and numerous long plumose hairs on 

 both margins. 



Telson cleft to the base, the lobes furnished distally with two or 

 three spines and a few hairs. 



Length, 10-15 mm. 



Distrihution. — Hudson River and Niagara Falls, New York; Ann 

 Arbor, Michigan; Lake Superior; Delavan and Lake Geneva, Wis- 

 consin; Havana, Illinois; Burlington, Iowa; Redf oot Lake, Tennessee; 

 Brookside, West Virginia; Washington, District of Columbia; St. 

 Johns River, Florida. 



GAMMARUS LIMNiEUS Smith. 



Gammarus lacustris Smith, Aiiier. Jour. Sci., 3<l ser., II, 1871, p. 453; Prel. 



Eept. on Dredgings in Lake Superior, 1871, p. 1023. 

 Gammarus limna'us Smith, 7th Kept. U. S. Geol. Survey, 1874, p. 609; Kept. U. S. 



Fish Com., 1872-73, p. 651, 1874. 

 Gammarus robustus Smith, 7th Kept. U. S. Geol. Survey, 1875, p. 610. 



Eyes small, slightly elongated. First antennae about as long as the 

 thorax; first and second segments of the peduncle nearly equal, twice 

 as long as the third; flagellum composed of about thirty elongated 

 segments, which are furnished with few hairs; secondary flagellum 

 composed of two to four segments, of which the terminal one is short. 

 Second antennae slightly shorter than the first; peduncle exceeding 

 that of the first pair with the two distal segments nearly equal in 

 length; flagellum shorter than or nearly equal to the peduncle, con- 

 sisting of about twelve segments. 



First gnathopods of the male with the carpus broadl}^ triangular, as 

 broad as the propodus; propodus a little less than twice as long as 

 broad^ much narrowed distall}"; palm very oblique, continuous with 

 the posterior margin, and having a lamellar edge furnished with a few 

 long hairs, and two long obtuse spines near the middle, and three or 

 four smaller spines on each side near the posterior angle; dactyl 

 strongly curved and about one-half as long as the propodus; lateral 

 margins convex, the posterior one furnished with a few long hairs 

 and several short, obtuse spines. In the female the propodus is con- 

 siderably smaller and proportionally shorter than in the male; palm 

 oblique, with a narrow lamellar edge continuous with the posterior 

 margin, furnished with a few long hairs, and sev^eral spines on each 

 side of the tip of the closed dactyl; posterior margin furnished with 

 several short spines, and numerous long hairs arranged in several 

 fascicles. 



Carpus of the second gnathopods in the male slightly longer than in 

 the first pair; propodus as long as in the first pair, slightl}^ broadest 

 distally; lateral margins nearl}^ parallel, posterior one furnished with 

 five or six fascicles of long hairs; palm slightly oblique, concave at the 



