PCECILOPODA. 



445 



joint of the leo^ being terminated on tlie inner edge by five small, corneous, narrow, elongated, pointed, and move- 

 able plates, and the two fingers are moveable, or articulated at the base. The two pieces situated between these 

 feet, considered by Savigny as a tongue, appear to me to be the two maxillary lobes of these organs, detached and 

 free. The males are distinguished by the form of the claws of the two or four fore-legs, which are swollen, and 

 destitute of a moveable finger. The two terminal legs of the anterior shield are united into a large, membranous 

 leaflet, nearly semicircular, bearing the se.xual organs on its posterior face ; the joints are indicated by sutures. 

 The second piece of the shell is nearly triangular, and notched at its posterior extremity. Its sides are alternately 

 notched and toothed, and with six spines on each side. In its concave under-side are situated, arranged in pairs, 

 and in two longitudinal series, ten fin feet *, nearly resembling the posterior pair of legs, but united merely at the 

 base, applied upon each other, and bearing on their posterior face the branchiae, which appear to consist of very 

 numerous fibres. 



These Crustacea sometimes attain the length of two feet. They chiefly inhabit tropical seas, and are found near 

 the shore. They appear to be peculiar to the East Indies and coast of America. In the latter part of the world 

 they are called Casserole Fish, — their shells serving, when the legs are removed, to lade water with. 



According to M. Leconte, a learned naturalist, they are used for feeding pigs. The natives use the horny style 

 at the extremity of the body in making their arrows, the point being dangerous. Their eggs are eaten in China. 

 In walking, their legs are not seen. Fossil species have been found in strata of moderate age. — Knorr, Mon. De- 

 luge, i. pi. 14 ; Desmarest, Crust. Fossiles, xi. 6, 7. 



One species, forming Leach's genus Trachyplceus, has the fdur fore-legs, at least in one sex, terminated by a 

 single finger, — L. heterodactylus, which I have observed figured in Chinese drawings, and which is probably the 

 Kabutogani or Unkia of the Japanese, by whom it is figured in their primitive Zodiac as the representative of the 

 constellation Cancer. In the others, the two fore-claws, at most, are only monodactyle. AH the ambulatory legs 

 are didactyle, at least in the females. This division is composed of numerous species ; but which, in consequence 

 of the slight attention which has been bestowed upon the details of them, from the differences of sex and of age, 

 together with their peculiar localities, have not been yet characterized with sufficient nicety. Thus, for example, 

 the young of the common American Lhnulus is whitish, with six strong teeth on the central ridge of the base, and 

 two on each of the lateral ridges ; but in others of greater age, and which are a foot and a half long, the colour is 

 much darker, and the teeth have nearly disappeared. We may refer the Limulus Cyclops, Fabr., L. Sowerbii, 

 Leach, L. iridentatus. Leach, and L. alius, Bosc, to the former ; and to the latter the Monoculus polyphemus, 

 Linn., which I had named L. moluccamis, considering it peculiar to the Moluccas. In all its states its tail is 

 shorter than the body, and denticulated above, which distinguishes it from other species described by myself and 

 Dr. Leach. — See Nouv. Did. d^Hist. Nat., second edition, and Desmarest. 



[Van der Hoeven has recently published two memoirs on this genus, in his Magazine of Natural History, pub- 

 lished at Amsterdam.] 



THE SECOND FAMILY OF P(ECILOPODA,— 



SiPHONOSTOMA, 



Does not exliibit any kind of jaws. A sucker, or siphon — sometimes external, and in the form 

 of an acute inarticulated beakf, — sometimes concealed, or nearly indistinct — occupies the place 

 of the mouth. The number of feet never exceeds fourteen. The shell is very slender, and of 

 a single piece. All these Entomostraca are parasites. 



We divide this family into two tribes, [Caligides and Lern^iformes]. 



The first of these tribes — that of the Caligides, Latr. — is characterized by the presence of a shell, 

 in the form of an oval or semi-lunar shield; by the number of visible legs, which is always twelve (or 

 fourteen, if, with Dr. Leach, we regard the limbs, which I consider as inferior antennae, as legs) ; by the 

 form and size of those of the ten posterior J, which are either slit into many parts, pinnated, or termi- 

 nated in a swimmeret, and well fitted, in all their stages of existence, for swimming : sometimes they 

 are leaf-like, broad, and membranous. The sides of the thorax never exhibit any wing-bke expansions 

 directed backwards, and posteriorly inclosing the body. [The tribe is divisible into two subtribes.] 



In the first subtribe, the body — exhibiting, on the upper side, several segments — is elongated, and 

 narrowed posteriorly, terminating in a tail with two filaments, or two other exserted appendages, at the 

 tip. This extremity of the body is not covered by a division of the superior integuments, in the shape 

 of a large rounded scale, deeply notched at its posterior extremity. The shell occupies at least the 

 moiety of the length of the body. This subtribe comprises two genera of Miiller [^Argulus and Califfusi . 



* The two fore-legs may represent the mandibles of the Decapods ; 

 the four following feet, their maxillte, and the sis hind-legs, their 

 foot-jaws : so that the fin-feet of the second part of the shell would 

 thence be the representatives of the thoracic legs of the higher 

 Crustacea. 



t The composition of this beak is not well understood. It is evi- 

 dent, from Jurine's figure of Argului foliineiit, that it incloses a 



sucker ; but is it the same with the others ? and what is the number 

 of the pieces of which it is composed ? This we are ignorant of, 

 although I presume that it consists of a labrum, mandibles, and a 

 tongue, which forms the sheath of the sucker. 



J [Latreille says, '* dix dcrni^res paires ;'* but he evidently intended 

 only x\\cfive posterior pairs, or ten posterior legs.] 



