CRUSTACEA. 
155 
FIRST GENERAL DIVISION. 
MALACOSTRACA. 
The Malacostraca naturally divide themselves into those whose eyes 
are placed on a movable pedicle, and those in which they are sessile 
and fixed. 
a. Eijes placed on a movable and arlicxdaled pedicle. 
Eyes* placed on a movable pedicle composed of two articulations, 
and received into fossulae, distinguish the Decapoda and Stomapoda 
from all the others. Anatomically considered, they appear to be still 
further removed from them, — Lefons d’Anat. Compar., Cuv. ; Ann. 
dcs Sc. Nat., t. XI, — inasmuch as they are the only ones that present 
sinuses in which the venous blood is collected previous to its trans- 
mission to the branchiae on its return to the heart. 
The Decapoda and Stomapoda resemble each other in several cha- 
racters common to both. A large plate, called a shell, covers a 
greater or less extent of the anterior portion of their body. They all 
have four antennae f, the middle ones of which are terminated by two 
or three filaments; two mandibles, each of which, at its base, bears a 
j)atpus that is divided into three joints, and usually laid on it; a bilo- 
bate tongue; two pairs of jaws ; six foot-jaws, the four jjosterior of 
which, in some, arc transformed into claws; and ten feet, or fourteen, 
in those where the four foot-jaws have that form. 
In the greater number the branchiee, of which there are seven 
pairs, are concealed under the lateral margin of the shell ; the two 
anterior pairs are situated at the origin of the four last foot-jaws, and 
the others at that of the feet properly so called. In the other Crus- 
* Beliind the coi'iiea, according to Blainville, is a choroides perforated with nume- 
rous holes; then a true crystalline, resting on a nervous ganglion, and divided into 
a multitude of little fasciculi. 
t We must distinguish the peduncle — sHpes , — and the stern — caulis funievUs. Tire 
peduncle is thicker, cylindrical, and composed of three joints, a number which seems 
peculiar to these organs in their imperfect or rudimentary state. The stem is seta- 
ceous, and divided into a variable number of very small joints. That of the exter- 
nal antennfE is simple, but that of the interior ones, consists of at least two filaments, 
and in several of the Decapoda Macroura, of three. Passing gradually from these 
latter to the Brachyura, the antennae become shortened, so that, in several of the 
Quadrilatera, the lateral ones, at least, are very small. In this case the two termi- 
nal divisions of the intermediate ones form a sort of bifurcated forceps, or unequal 
and articulated fingers. 
