CLASS CRUSTACEA. 
139 
MALACOSTRACA WITH EYES SUPPORTED ON A MOVE- 
ABLE AND ARTICULATED PEDICLE, OR DECAPODA 
AND STOMAPODA IN GENERAL. 
Eyes supported on a mobile pedicle, of two articulations, 
lodged in fossets, distinguish these Crustacea from all others. 
Considered anatomically, they appear to be still more remote 
from them, inasmuch as they are the only ones which present 
sinuses where the venous blood collects, before repairing to 
the gills to return to the heart. 
The decapoda and stomapoda resemble each other in many 
common characters : a large shell, sometimes divided in two, 
called testa or carapace, covers in front a more or less ex- 
tended portion of the body. They all have four antennas, of 
which the middle are terminated by two or three threads ; two 
mandibles, with a palpus near the base of each, divided into 
three articulations, and usually inclined upon the mandibles ; 
a bilobate tongue ; two pair of jaws ; six jaw-feet, but the four 
posterior of which are in some transformed into claws; tenor 
fourteen feet, in those in w r hich the four jaw-feet have this 
form. 
In the greater majority, the gills, seven pair in number, are 
concealed under the lateral edges of the testa ; the two ante- 
rior pair are situated at the origin of the last four jaw-feet, and 
the others at that of the feet properly so called. In the other 
Crustacea, they are annexed, under the form of tufts, to five 
pairs of feet like fins, situated under the post-abdomen ; the 
under part of this posterior portion of the body is equally 
furnished in the others with four or five pairs of bifid 
appendages. 
