Order 1. DECAPODA. 421 



is always prolonged into a point, often forming a sharp-pointed plate, very much compressed, and 

 toothed on hoth edges. The antennae are always advanced ; the lateral ones generally very long, and 

 in the form of a very slender thread : the intermediate antenna, in the majority, are terminated by 

 three filaments. The eyes closely approach each other. The outer foot-jaws, longer than ordinary, 

 resemble palpi or antenns. One of the two fore pair of legs is often folded back, or doubled. The seg- 

 ments of the tail are dilated laterally. The outer plate of the terminal swimmeret is always divided ia 

 two by a suture, as in the terminal species of the preceding section. The middle piece, or the seventh 

 and last segment of the tail, is long, narrowed towards the tip, and is armed above with rows of small 

 spines. The false legs, of which there are five pairs, are long and foliaceous. These Crustacea are much 

 eaten in different parts of the world, and some species are salted for keeping.* 



Tliose which have the three anterior pairs of legs didactyle, the length gradually increasing, so that the third 

 pair is the largest, compose the genera Peiiceiis, Fabr., (having no annular divisions in the joints of the legs, and 

 composed of numerous species, one of which, the Caramote (P. siilealt/s, Oliv.), is very common in the Mediter- 

 ranean, and is a great object of commerce, being salted for exportation to the Levant, and of which the English 

 species {P. trimlcatus, Leach) is considered by Latreille to be a local variety),— and Stenopus, Fabr., having the two 

 penultimate joints of the four posterior legs with annular divisions. 



The remaining species have not more than the two anterior pairs of legs didactyle, and the intermediate antennae 

 terminated by three iilaments. 



Ati/a, Leach, formed of a single North American species, A. scabra, is anomalous in the form of its four claws, 

 which are small, and split to the base with long terminal pencils of hair, the preceding joint being crescent-shaped. 



The others have the claws of the ordinary didactyle form. These, with the exception of the terminal genus, have 

 the legs more or less robust, but not filiform, without any appendage at the base. The body is neither very soft, 

 nor very much elongated. 



Crangon, Fabr., has the fixed finger or index of the two anterior and largest claws reduced to a small tooth, the 

 moveable finger being hook-shaped. The superior or intermediate antennae have only two terminal filaments ; the 

 second legs are foldetl, and more or less distinctly didactyle at the tips ; none of the joints are annulated ; the 

 rostrum is very short. Crangon vulgaris, Fabr., the Common Shrimp, is the type of this genus. It does not 

 exceed two inches in length, and is of a pale glaucous green colour, dotted with grey. It is caught throughout 

 the year with the assistance of circular nets. Its flesh is delicate. 



PontopMlus, Leach (Egeon, Risso), does not generically dift'er from Crangon. 



Processa, Leach {Nika, Risso), has one of the fore-legs terminated in a point, and the other didactyle. The 

 second pair of legs are of unequal length, one being very long, with the two joints preceding the claw annulated. 

 N. edidis, Risso, found at the mouth of the Rhone. 



Hymenocera, Latr., diflfers in the proportions and form of the legs. 



To these succeed a number of genera in which the legs and claws do not present any anomalous structure, and 

 in which the superior or intermediate antennae have only two terminal filaments, including the genus Hippolyte, 



Leach, comprising several British species of shrimps, and in which the four fore-legs 

 are terminated by a didactyle claw, the second pair being longer than the first ; and 

 Pandalus, Leach, comprising another British species (P. annulicornis. Leach), in 

 which the fore-legs are [very small and] simple, or scarcely bifid ; the two following 

 long, of unequal length, with the two joints preceding the claw annulated. 

 ^. , „. , The Prawn is the type of the genus Palamon, which difters from the last group 



Fig;. 7 —Hippolyte vanans. / 1- o 



of genera in having the upper antennae terminated by three filaments. It has 

 the two anterior pairs of legs didactyle, the smaller pair being folded ; and the carpus is not articulated. The 

 rostrum is very long [and spined]. Some of the exotic species acquire a very large size, with the second pair of 

 legs very long. The flesh of the common species is more esteemed than that of the Shrimp. According to M. 

 de Brebisson {Cat. Meth. Crust. Depart, du Calvados), they are caught in the same manner as Shrimps, but only 

 in summer. They swim well, especially when alarmed, and in different directions. They frequent the coast. The 

 lithographic stone of Pappenheim and Sohlnofeii often contains the remains of a fossil species, which Desraarest 

 names Palamon spinipes. Another fossil species, but of a much larger size, has been found in England. The 

 species ordinarily sold in the fish-shops is the Palamon serratus. It is generally three or four inches long, and of 

 a pale red colour, which is brightest in the antennae, and especially in the swimmeret of the tail. Its frontal spine 

 extends beyond the peduncle of the middle antennae : it is curved upwards at the tip, with seven or eight spines 

 above, and five beneath. One of the sides of the body is often distended, which is caused by a parasite of the 

 genus Bopyrus beneath the carapax, affixed to the branchiae. Palcemon squilla, Linn., is another but smaller 



• [The jjradual developenient of several species of Carides (Palw- 

 n»oiud») has been recently riesoribed by I)r, J. V. Thompson in Jauie. 

 son's Ednib. Phil. Juiirii., Oct. 1836, and by Captiiin Ducane in the 

 .iuiinh u/ Nut. Hist., Xov. 1838. On Brst bursting from the egg, the 

 trtil is teruiinated by a spatulated plate, destitute of lateral as well as 

 lubalxloniinal appendages; the rostrum is produced into a simple 



and ridge of the carapax spined ; the five pairs of legs extended to 

 their lull size, hut still bifid ; and the suhabdominal appendages and 

 the swinimcrels gradually developed. These observations are as- 

 serted, by l^I'Leay and others, to afford a complete confirniation of 

 the correctness of Thompson's assertions that Zoea is the larva of the 

 conirjion Crab, and that all the Crustacea under^ro transformations, — 



point ; the lateral antennae exhibit only the large scale ; and only t-.vo these geiitlemen overlooking the fact that Zoea is a Decapod animal. 



of the legs are of the ordinary length, and these are bifid, us in the 

 Schizopods : the other legs are very minute, and incurved. In the 

 *ourse of several moultin({s, the anteiins are lengthened ; the rostrum 



not furnished with bifid legs, but having the two pairs of outer foo 

 jaws immensely uevelooed, but of the ordinary Macrourous construe 

 tion, as arc the interaal parts of its mouth.] 



