ORDER DECAPODA. 193 



HiPPOLYTE, Leach, 



Are removed from Alpheus only by the respective proportions 

 of the claws ; the second are longer than the first. {Palaemon 

 diver simana, Oliv.) 



The last two subgenera following, have this peculiarity, 

 that one pair only of their feet is terminated in a didactylous 

 forceps. In 



Antonomea, Risso, 



It is the two anterior, which are distinguished from the 

 others, by their size, thickness, and disproportion. {Antonomea 

 Olivii, Risso.) 



Pandalus, Leach. 



The two anterior feet are simple, or scarcely bifid ; the two 

 following are longer, of an unequal length, didactylous, with 

 the carpus and the preceding articulation annulated. 



The external jaw-feet are slender and very long, at least in 

 some; the anterior projection of the testa is very long and 

 much denticulated. {Pandalus amiulicornis, Leach.) 



Sometimes the upper antennae have three threads ; these 

 Crustacea have four didactylous claws, the smallest of which 

 are folded and the bill elongated. 



Pal^mon, Fah., 



Are distinguished from the two following subgenera, by their 

 inarticulated carpus ; the second feet are larger than the first ; 

 these last are folded. (P. serratus, Leach.) 



The carpus is articulated, or presents some annular divi- 

 sions in the two following subgenera : 



Lysmata, Risso, 



Which have the second pair of claws larger than the first. 

 [Lysmata seticcmda, Risso.) 



• VOL. XIII. O 



