220 CRUSTACEA. 



of the species do we find those long oar-like cirri observed in the first 

 of the lones. 



In the latter, when it exists, the moveable toe of the foot, termi- 

 nated by a forceps, is formed of a single joint. 



Of these last, there are some whose superior antennee are much 

 shorter than the inferior, and even than tlieir iieduncle; the stem of 

 the latter is composed of numerous joints. 



Orchestia, Leach. 



The second feet of the male terminated by a large forceps, the 

 moveable toe long and somewhat curved ; those of the female by two 

 toes. The third joint of the inferior antennae is at most twice the 

 length of that of the j)receding ones *. 



Taliprus, Lai. 



Neither of the feet forming a forceps. Tlie third joint of tlie in- 

 ferior antennae more than twice the length of that of the preceding 

 ones ; the antennae large and spinous f . 



In tlie following, the superior antennae are never much shorter 

 than the inferior. 



Some of them, furnished with elongated setaceous antennae ter- 

 minated by a pluri-articulated stem, and without any remarkable 

 forceps, approach the preceding in tlieir superior antcnnrc, which 

 are somewhat shorter than the inferior, and are removed from those 

 that follow by the form of their head which is narrowed before into a 

 kind of snout. Such is 



Atylus, Leach \. 



All those which succeed have the superior antennae as long as the 

 inferior, or longer; their head is not elongated into a snout. 



Here, as in the five following genera of Leach, the peduncle of the 

 antennae is formed of three joints §. 



Some, in their superior antennae, present a character which is 

 unique in this order— the internal extremity of the third joint of the 

 peduncle is provided with a little articulated thread. It distinguishes 

 the 



Gammarus, Lai., 



AVhere the four anterior feet have the form of small forceps, the 

 moveable toe folding beneath. 



■» Oniscus gammardlus, Pall., Spic. Zool., Fascic, IX, iv, 8: Cancer gammarus 

 Ullnreus, Montag. ; Desmar., ConsicL, p. 26 1, XLV, 3. 



T Onisciis locusfa, Pall., Spie. Zool., Fascic. IX, iv, 7 ; Cancer gammarus saltator, 

 Montag. ; Desmar., Consid., XLV, 11. 



+ ^/(/?KS ra>-in«^MS, Leach, Zool. Misc., LXIX ; Desmar., Consid., p. 262, XLV, 

 4; Gammarus carinafus, Fab.; — G. migux ' ejusd. ; Phipps, Voy. to the North 

 Pole, XII, 2 ; 



§ The third joint of the peduncle may be very small and thus become assi- 

 milated to the following, or those of the stem; this peduncle, as in the Dexamiues, 

 then appears to consist of but two joints. According to the system of Leach the 

 stem is understood to form another but compound joint. 



