CRUSTACEA. 
210 
inferioiiy, and hence the denomination of Stomapoda affixed to this 
order. Judging by the Sqiiillse, the most remarkable genus of this 
order, and the only one hitherto studied, the heart is elongated, and 
similar to a large vessel. It extends along the whole length of the 
back, rests upon the liver and intestinal canal, and terminates poste- 
riorly and near the anus in a point. Its parieties are thin, transparent, 
and almost membranous. From its anterior extremity, placed imme- 
diately behind the stomach, arise three principal arteries, the mediate 
of which — the opthalmic — giving off several branches on each side, is 
more particularly directed to the eyes and intermediate antennae ; and 
the two lateral ones — the antennaries — pass over the sides of the 
stomach and are lost in the muscles of the mouth and of the externa l 
antennae. No artery arises from the superior surface of the heart* 
but a great many issue from its two sides, each pair of which, as it 
appears to us, corresponds to a particular segment of the body, com- 
mencing with the foot-jaws, whether these segments be external, or 
concealed by the shell, and even very small, as is the case with those 
that are anterior. On a level with the first five abdominal annuli, or 
those to which the natatory appendages and the branchiee are at- 
tached, this superior surface of the heart receives, near the median 
line, five pairs of vessels — a pair to each segment — proceeding from 
these latter organs, and which, according to Messrs. Audouin and 
Milne Edwards, are analagous to the branchio-cardiacs of the Deca- 
poda. A central canal * situated under the liver and intestine re- 
ceives the venous blood which is poured into it from all parts of the 
body. On the level of each segment to which the foot-jaws and 
branchise are attached, it gives off a branch on each side, running to 
that part of the branchiae which is situated at the base of the cori’e- 
sponding foot-jaw. The parieties of these vessels appear to the above- 
mentioned gentlemen to be smooth and continuous, but formed by a 
layer of lamellated cellular tissue glued to the neighbouring muscles, 
rather than by a membrane proper ; these vessels also a])peared to 
them to communicate with each other near the lateral margin of the 
annuli, but they could not possitively affirm it. The afferent or in- 
ternal vessels of the brancluBe, which in these SquillEe form tufted 
bunches, are continuous with the branchio-cardiac canals, are no 
longer lodged in cells, pass between muscles, turn obliquely over 
* See our general observations on the Macroui-a. Neither this vessel nor the 
venous sinuses have been observed in the subsequent orders ; but the heart preserves 
the same elongated form, and presents similar anterior arteries. From its sides also 
arise other arteries corresponding to the articulations of the body. In addition to 
the pre-cited Memoir, see the Le9ons d’ Anatomic Comparde of the Baron Cuvier. 
