SlO CRUSTACEA. 



inferiorly, and hence the denomination of Stomapoda affixed to this 

 order. Judging by the Squillte, 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 tlie mouth and of the extei'nal 

 antennae. No artery arises from the superior surface of the hearts 

 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 branchiae 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 

 branchiae 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 corre- 

 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 mviscles, 

 rather than by a membrane proper ; these vessels also appeared 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 branchiae, which in these Squillae 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 Macroura. 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'Anatomie Compar^e of the Baron Cuvier. 



