NO. 1507. 



FRESH- WA TER AMPHIPODA— WECKEL. 



55 



First onathopods in the male more than half as broad as long; lateral 

 margins strongh^ curved and furnished with minute spinules; palm 

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

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

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

 gnathopods in the female closely resemble those in the male. 



Second gnathopods of the male much longer than the tirst ones; 

 carpus not longer than broad, with a long narrow lobe extending along 

 the posterior margin of the propodus; propodus stout, more than half 

 as broad as long, much broadened distally, especially in the mature 



ur. I 



Fig. 15.— Hyalella knickerbockeei. Ann Arbor, Michigan, (jn. 1$, gn. 2 9, first and second 



GNATHOPOD.S OF THE FEMALE; OTHER FIGURES OF THE MALE. gv. 2', SP;COND GNATHOPOD OF A 

 YOUNG male; gtl. 2, SECOND GNATHOPOD OF A MATURE MALE. 



specimens; anterior margin convex; posterior one straight, oblique, 

 and unarmed; palm oblique, the middle portion slightly arcuate, with 

 a notch near the middle and one or two slight emarginations at the 

 posterior angle; provided with a submarginal row of spines; palm in 

 immature specimens transverse, emarginations very slight, dactjd not 

 so strongly curved as in the adult. Second gnathopods of the female 

 slender and weak; carpus and propodus elongated and much narrower 

 than those of the male; carpus more than twice as long as broad, pos- 

 terior projection proportionally not so great as in the male; propodus 

 more than twice as long as broad; palm forming less than a right 



