192 
CLASS CRUSTACEA. 
ceding articulation annulated; tliis character is proper to the 
other foot only at the first of these articulations ; the feet of the 
fourth pair are longer than the preceding and the two following; 
the upper antenna} have but two threads. ( Nika edulis, Risso.) 
Hymenocera, Lair., 
Have the two anterior feet terminated by a long hook, bifid 
at the end, and with very short divisions ; the two following- 
are very large : the hands, the fixed finger, and the upper 
thread of the middle antennae are dilated, membranaceous, 
and, as it were, foliaceous ; the external j aw-feet are likewise 
foliaceous, and cover the mouth. 
We shall now pass to some subgenera in which the claws 
present no remarkable or unusual particularity. 
Sometimes the upper or middle antennae are terminated but 
by two threads ; the bill is generally short. 
Gnathophyllum, Lair., 
The only ones, which, in the relation of the form and amplitude 
of the lower jaw-feet, approach liymenocera ; the four anterior 
feet are in the form of didactylous claws ; the second pair is 
longer and thicker than the first ; none of the articulations of 
the four are annulated. ( Alpheus elegans, Risso.) 
Pontonia, Latr., 
Have, like the two following subgenera, the four anterior feet 
in the form of claws, and didactylous, but the carpus is not an- 
nulated. ( Alpheus thyrenus, Risso.) 
Alpheus, Fab ., 
Which have also the four anterior feet terminated by a 
didactylous forceps, but the carpus of the second is articu- 
lated ; these last are shorter than the first. ( Alpheus mala- 
baricus, Fab.) 
