190 
CLASS CRUSTACEA. 
Pen^eus, Fab ., 
In which no articulation of the feet presents any annular 
division ; their mandible-palpi are raised and foliaceous. 
We see a small appendage, in the form of an elliptical plate, 
at the base of the feet, a character which seems to approach 
these Crustacea to pasiphae, the last subgenus of this section, 
and to those of the following, (. Palcemon sulcatus , Oliv.) 
Other penaei have the intermediate antennae terminated by 
long threads; these are those of our second division. ( Pen mis 
monodon , Fab.) 
Stenopus, Latr ., 
Are distinguished from the last by the transverse and annular 
divisions of the two articulations before the last, of the four 
posterior feet; all the body is soft: the antenna? and feet are 
long and slender; those of the third pair are the broadest. 
( Cancer seti ferns, Linn.) 
The other Carides, many of which have the intermediate 
antennae terminated by three threads, present at most but 
two pair of didactylous claws, formed by the four anterior 
feet. 
A subgenuc established on a single species proper to North 
America, that of 
Atya, Leach , 
Is removed from all the analogous Crustacea, by an anomalous 
character; the forceps terminating the four claws is cleft as 
far as its base, or appears to be composed of two lingers in 
the form of lashes, united at their origin; the articulation 
which precedes, is in the form of a crescent ; the second pair is 
the largest ; the middle antennae have but two threads. ( Atya 
scabra , Leach.) 
In all the following subgenera, the fingers of the forceps 
arise only at a certain distance from the origin of the last 
