FRESIMYATKR AMPIi I PODS KKOM l'KKU. 



By Ada L. Weckel. 



Oak Park High School, Oak Park, Illinois. 



The single species of fresh-water Amphipod was taken in vast 

 abundance at Lake Titicaca, July 30, 1908, underneath small rocks 

 along - shore of Isla Blanca (near - Puno). 



HYALELLA KNICKERBOCKER! (Bate). 



Allorchestes knickerbockeri Bate, Cat. Amph. Crust. Brit. Mus., L862, p. 36, pi. 6. 

 Hyalrlln knickerbockeri Weckel, Proc; I . S. Nat. Mus., vol. 32, 1907, p. 54, text 

 fig. 15, and synonymy. 



Eyes round or nearly so; interspace slightly greater than their 

 diameter. First antennae shorter than second; first two segments of 

 peduncle about equal, slightly longer than third; flagellum about 

 twice as long as peduncle and composed of seven to nine segments; 

 second antenme about half as long as body; peduncle exceeding that 

 of first pair, the two distal segments elongated and nearly equal; Ila- 

 gellum usually but little longer than in first pair, composed of eight 

 to fifteen segments. 



First gnathopods in male more than half as broad as long; lateral 

 margins strongly curved and furnished with minute spinules; palm 

 transverse, concave at middle, provided with a few small teeth 

 and short hairs at posterior angle and a tuft of long stiff hairs at 

 anterior one; dactyl strongly curved, shorter than palm. First 

 gnathopods in female closely resemble those in male. 



Second gnathopods of male much longer than first ones; carpus not 

 longer than broad, a long, narrow lobe along posterior margin of 

 propodus; propodus stout, more than half as broad as long, much 

 broadened (list a 11 v, especially in mature specimens; anterior margin 

 convex; posterior one straight, oblique, and unarmed; palm oblique, 

 middle portion slightly arcuate, with a notch near middle and one or 

 two slight emarginations at posterior angle; provided with a sub- 

 marginal row of spines; palm in immature specimens transverse, 

 emarginations very slight, dactyl not so strongly curved as in adult. 



Proceedings U. S. National Museum, Vol. 38— No. 1768. 



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