182 
CLASS CRUSTACEA. 
number. The two middle antennas are never terminated but 
by two threads, and generally shorter than their peduncle, or 
scarcely longer. The external leaf of the natatory appen- 
dages of the last segment of the tail but one, is never divided 
by a transverse suture. 
Our second section, Locusta, thus designated from the 
word locusta , applied by the Latins to the most remarkable 
Crustacea of this division, from which comes the French word 
langouste , have al ways but four pair of false feet. The pos- 
terior extremity of the fin terminating the tail is always almost 
membranaceous, or less solid than the rest. The peduncle of 
the middle antennae is always longer than the two threads of 
the end, and more or less folded or bent ; the lateral ones are 
never accompanied with scales : sometimes they are reduced 
to a single pedicle, which is dilated, very much flatted, and in 
the form of a crest ; sometimes they are large, long, going into 
a point, and entirely bristling with prickles. All the feet are 
almost similar, and go into a point at the end ; the first two 
are simply a little stronger. Their penult articulation, and that 
of the two last, is at most unidenticulated, but without form- 
ing with the last a hand perfectly didactylous. The pectoral 
space comprised between the feet is triangular. The thorax 
is almost square or subcylindrical, without any frontal prolon- 
gation, in the manner of a pointed bill or lance. 
Scyllarus, Fab., 
Present, in the form of their lateral antennse, a character al- 
together unusual ; the stem is wanting, and the articulations 
of the peduncle, very much dilated transversely, form a large 
crest, flatted, horizontal, and more or less denticulated. 
The external branch of the subcaudal appendages is ter- 
minated by a leaf, but the internal, in some males, only shows 
itself in the form of a tooth. 
According to the proportions and form of the thorax, the 
