544 



E. W. SEXTON. 



A large female had twenty in the one and four in the other, the 

 liagella being shorter and more setose than in the male. 



Antenna 2 (Fig. 3) of the male forms one of the distinguishing 

 characters of this species, easily separating it from the other species of 

 Gammarus. The fourth and fifth joints of the peduncle and the 

 flagellum (excepting the four terminal joints) are clothed on the inner 

 surface as well as on the inferior margin with dense tufts of long 

 exceedingly fine sensory hairs. These hairs have very delicate coiled 



Fig. 3. — Antenna 2. 6 Gammarus chcvreuxi, w. &\^. Inner side. x 27. 



tips and are found only in the male, on the second antennae, the 

 iZnathopods, the first peraeoj)ods, the third uropods, and the telson. 

 The fiagellum in the male is sixteen-jointed. The female has only a 

 few clusters of long outstanding straight setae on the fourth and fifth 

 joints of the peduncle, and short setae on the flagellum. 



Gnafhojwds 1 and 2 rather small, not much difference in their size. 

 In the male, Gnath. 1 (Fig. 4) has the sixtli joint pyriform, palm 

 oblique, indented, witli one stout truncate spine midway on the palmar 



Fig. 4. — Gnathopod 1. S Gammarus chcvreujn, n. sp. Inner side, x 27. 



margin, angle defined by spines ; finger much curved, impinging against 

 the inner surface of the hand. In Gnath. 2 (Fig. 5) the hand is 

 broader, palm slightly oblique. In both gnathopods the hand, espe- 

 cially on the inner side, is provided with numbers of the coiled sensory 

 hairs, the fifth joint also carrying a few. 



In the female the fifth and sixth joints of Gnatli. 1 are practically 

 subequal in length, but the fifth is much wider distally than the sixth; 



