Order 2. 



STOaiAPODA. 



423 



penda.re at the base, the fourth pair bein^r the long'est. I only know one species (M. Lcsueiiiii), collected in the 

 seas of North America. Olivier found, in the Penna marina, a crustaceous animal very similar at the first 

 sight ; but the specimens were so much injured that 1 was not able to study its characters. 



The Nebalia, which I had at first placed in this section, not having any natatory appendages under 

 the terminal segments of the hody, and their legs being very similar to those of Cyclops, I have intro- 

 duced, together with Cnndylura, at the head of the order Branchiopoda. Nehalia, in its exposed eyes, 

 which appear to be pedunculated, and in some other characters, seems, in conjunction with Zoea, to 

 unite the Schizopoda with the Branchiopoda. 



THE SECOND ORDER OF CRUSTACEA,— 



STOMAPODA (commonly called Sea-Mantes),— 



Have the branchiae naked, and adhering to the five pairs of appendages attached beneath the 

 abdomen or tail, which this part of the body also presents to us in the Decapods, which 

 appendages here, as in the majority of the Macroura, are used in swimming, or are fin-feet. 

 The carapax is divided into two parts, of which the anterior bears the eyes and intermediate 

 antennae, or more properly composes the head without supporting the foot-jaws. The latter 

 organs, as well as the four fore-legs, often closely approach the mouth in two lines, converging 

 inferiorly : whence arises the name Stomapoda, given to this order. 



The heart — to judge at least from the Squillce, the most remarkable genus in the order, 

 and the only one in which it has been studied — is elongated, and resembles a large vessel ex- 

 tending the whole length of the back, and terminating posteriorly near the anus, in a point. 

 The teguments of the Stomapoda are slender ; and, in some species, almost membranous 

 and diaphanous. The carapax, or shell, is sometimes formed of two shields, of which the 

 anterior represents the head, and the other the thorax, sometimes of a single piece, but free 

 behind, leaving generally uncovered the thoracic segments, which bear the three hind pairs of 

 legs, and having in front an articulation serving as a base for the eyes and intermediate an- 

 tennae : the latter organs are always terminated by two or three filaments. The eyes are 

 always close together. The composition of the mouth is essentially the same as in the 

 Decapods ; but the palpi of the mandibles, instead of being adpressed to them, are always 

 raised. The foot-jaws are not furnished with the whip-like appendage {fouet) which exists in 

 the Decapods. They have the form of claw-legs, or small feet; and, in many at least {Squilla), 

 the base externally exhibits, as well as that of the two fore-legs, properly so called, a vesicular 

 body. The second pair of foot-jaws, in the same Stomapods, is much larger than the others, 

 and even than the legs themselves : hence they have been generally considered legs, and the 

 number of these organs has been stated to be fourteen.* The four anterior [true] legs have 

 also the form of claw-feet ; but are terminated, like the foot-jaws, by a hook which folds 

 upon the inferior and anterior edge of the preceding joint. But in some others, such as the 

 Phyllosomcef, all these organs are filiform, and without any didactyle claw. Some of these, 

 however, as well as the six hind-legs of the Squillce, are fm'nished with a lateral appendage or 

 branch. The seven terminal segments of the body — inclosing a considerable portion of the 

 heart, and to which the respiratory organs are attached — cannot, moreover, in this respect, 

 be considered analogous {assimiles) to that portion of the body which is called the tail in the 

 Decapods, being an abdomen, properly so called. Its penultimate segment has, on each side, 

 a swimmeret formed in the same manner as that of the tail of the Macroura, but often armed, 

 as well as the terminal segment or intermediate piece, with spines or teeth. 



All the Stomapoda are marine, preferring tropical chmates, and not going beyond the tem- 



• The second pair of true maxillie of, the Stjuiilts has not the sanie 

 form as in the Decapods, being of an elontjated, trian^lar form, di- 

 Tided into four joints by transverse lines. The mandibles are bifur- 



cate, and verv much notched. 



t In aU those which Iiave the four anterior feet claw-lilie, the six 

 posterior arc formed for swimming. 



