DECAPODA. 



421 



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

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

 in the form of a very slenrler thread : the intermediate antennae, in the majority, are terminated by 

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

 resemble palpi or antenna?. 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 in 

 t«.*o 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.* 



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

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

 composed of numerous species, one of which, the Caramote (P. sulcafus, 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. trisulcatus, Leach) is considered by Latreille to be a local variety),— and Stenoput, 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 

 terminate! by three filaments. 



Ali/a, Leach, formed of a single North American species, A. seabra, 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 beinsj crescent-shaped. 



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

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

 nor very much elongated. 



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

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

 second leys are folded, 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. 



Pontophilits, Leach (Egeon, Risso), does not generically differ from Crangon. 



Processa, Leach (Xika, 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. edtdi.s, Kisso, found at the mouth of the Rhone. 



Hymenocera, I.atr., differs 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 antenna; have only two terminal filaments, including the irenus lli/i/mli/tc. 



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. annulieornit, Leach i, 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 daw annulated. 



The Prawn is the type of the genus Paltcmon, which differs from the last group 

 of genera in having the upper antenna; 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 \ ery long [and spined]. Some of the exotic species acquire a very large size, w ith the second pair of 

 i gs very lotiir. The flesh of the common species is more esteemed than that of the Shrimp. According to M. 

 de Brebisson [Cat. Mi Ifi. ("rust. Depart, du Calvadot), they are caught in the same manner as Shrimps, but only 

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

 lithographic stone of Pappenheim and Sohlnofen often contains the remains of a fossil species, which Desmarest 

 names PaUnum ipinipe*. Another fossil species, but of a much larger size, has been found in England. The 

 species ordinarily sold in the fish-shops is the Pal.rmn,, s<-rr<itiis. It is general!] three or four inches long, and of 



r pale red colour, which is brightest in the antennae, and especially in the Bwin srel 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 t\ 

 above, and Ave beneath. One of the sides of the body is often distended, which is caused b) ■ parasite of the 

 genus Bopyrus beneath the carapax, affixed to the branchiae. Pabemon iquilla, Linn., is another but smaller 



• [The grednjel developament ol several ipedee of Cvldei 

 monldm] bet been rei enUj deeerlbed by Dr. J. v. Thompson »» Jetne- 

 son's Bdlnb. Phil. ./,■»,».. Oct. I8M, end by Captain Dncue in ilic 

 MnnaltoJ St. lint . Mot. 1838. Oi trel bantlof) from the egg, Oic 

 i.il ii terminated by a tpntulntcd platr, deedrule <>t Inert] .»> well a» 

 idomlnel eppendeguei the roecruui i» produced Into a tlmple 



Iteral entennSs exhibit uuly Ilic Urjfe scale ; ami only tWO 



vi the legs in ol the ordlnnry length, end tln-.r are bifid, a. In the 

 8 ]>inis ; the other lees ere ecrj minute, end Incurved. In tl><- 

 course »»f set erel nioultlnge, the eutennei wc Lengthened ; the roetram 



Fig. 7 — Illppolyte varlane. 



end rul^e of the ciri\|ia\ ipl I; the Ire i 



their full else, but itUI bifid ; end the lubebdomluel sppeudeges end 

 the nrlmmercts gradually developed. These observations ere »«- 

 terted, by MM. cay end others, lu afford » complete eonfirauaUon ol 

 the correctness ol Tl ipson's *■.«■ rtlons Ihm Zoea Is the l»r\» ol the 



in Crab, and thai all the Crustacea undergo tranafbrmatloaa,— 

 these genUemen overlooking ibe !•■ t thel . if „i animal, 



not furnished with blfld legs, bnt herlng the !»•• | i foot. 



iimeueerj develop! d, bu - 

 tluuj u are the Intcrusl psrts ol 



