DECArODA. 



417 



Tribe A ^Aschizojjoda, Westw.]. — Those -vvbich, in the proportiuiis, furrns, and uios of tiie feet, ilie 

 anterior, or at least the second, pair being cheliferoits, and which carrving tlieir eggs beneath tlieir 

 tails, approach the Brachyura, and whicli are ordinarily known under the names of Lobsters, Cray- 

 fish, Prawns, and Shrimps. Divisible into four sections: — l.Anomala; 2. LocnstEC ; 3. Astacini; 4. 

 Cariiles. 



Tribe B \_Schizopo(.la, Latr.]. — Those which have the legs slender and filamentous, accompanied by 

 an external articulated branch as long as the limbs, which thus appear doubled in number; fitted for 

 swimming, and not cheliferons, the eggs being carried beneath them, and not under the tail. [Opossum 

 Shrimps.]* 



Tlie first section [of the tribe Aschizopoda'], or the Anomala. — T!ie two or four hind legs are always 

 much smaller than the preceding. The under side of the tail never presents more than four pairs of 

 appendages, or false Icgs.f The lateral swimming-pieces at the extremity of the tail, or the paits whicli 

 represent them, are thrown liack at its sides, so as not to form with the terminal segment a fan-like 

 swimmeret. The ocular peduncles are generally longer than those of the Alacroura of the following 

 sections. [Two subsections, Uippides and Paguriens.] 



The subsection Hippides (Latr.) has all the upper teguments of the body solid. Tlie two fore-legs 

 cither terminate in a monodactyle or fingerless hand, like a plate, or they terminate in a point. The 

 six or foirr following legs terminate in a swiniming-platc. The two terminal legs are filiform, folded 

 back, and situated at the lower base of the tail, which is suddenly narrowed after the first segment, 

 which is short and broad, and of which the last is in the form of a long triangle. The lateral appen- 

 dages of tlie penultimate segment are in the form of bent swimming-plates. The sub-abdominal 

 appendages are four pairs, and formed of a very slender filiform stem. The antenna are A'ery pilose 

 and ciliated, the lateral at first approaching the intermediate, and then being l)cnt outwards. 



Alhunca, Fiibr., comprises a single species from tlie Indian Seas {Cancer Si/miusfa, Linn.) 

 [a sing-ularly formed animal], with loiip;, setaceous, intermediate antenna; the carapax tlat, 

 nearly square, rounded at the posterior anf,des ; a pair of very compressed, triangular, 

 monodactyle fore-legs,— the three following pairs terminated by a flat, sickle-shaped joint. 



H'lppa, Fabr., Emerita, Gronovius, has the antennae sbort, the intermediate with two fila- 

 [■ -yi' y ments longer than the external; the two fore-legs terminated by a very compressed claw, 



V^j^' \j^J without lingers ; the carapax ovoid. Type, Cancer Emeritus, Linn. Indian Seas. 



Remipes, Latr., differs from the last in the four antennae being very short, and nearly of 

 equal length ; the ocular peduncles very short, and in sonie other particulars. Type, R. 

 (fstudinarius, Latr, From the seas of New Holland. 



The subsection Paguriens has the teguments but slightly crustaceous ; and 

 the tail is generally soft, bag-like, and bent. The two fore-legs terminate in a 

 didactyle claw ; the four following terminate in a point ; and the four posterior 

 much shorter, in a small didactyle claw. The first joint of the peduncle of the 

 Tig. 5.— nemipf^s tfstii- lateral antennae presents an appendage ending in a point, or in form of a spine. 

 These Crustacea (which the Greeks named Carcinion, and the Romans Cancclli) 

 live, for the most part, in empty univalve shells. The tail, except in Birgus, only presents (and that 

 in the female alone) three false legs placed on one of the sides, each divided into two liliforni villose 

 branches. The three terminal segments are suddenly narrowed. 



Birgus, Leach, has the tail solid, snborbicular, with two rows of plate-blie appendages on the under side. The 



fourth pair of legs is but little smaller than the preceding ; the two posterior pair are [very small, and] hidden in 



1 groove in the extremity of the carapax. The carapax is in the shape of a reversed heart, being pointed in front. 



On account of their large size, the solid consistence of their teguments, and the form of the tail, these Crabs are 



not able to lodge in shells, but must retire to crevices in the rocks, or hide themselves in burrows in the earth. 



* 'Ilislierc [iroper tn observe, (Iiat in the recent Hrr.inge ments of 

 Miluc R(l\i'arfls ami M'Lesiy, tlic seventh (inti hisi section, Notopoda, 

 of J./itreille's arriiiErcuient of tlie Br;tchyiir.i, and liis first seetioii of 

 the Ulricroura, Anomala, conslitule one of ibe three primary divisinns 

 of ihe Dectipoda, forming, aa mn.y be readily per-jeived, ihe passage 

 I.etween tlie Brachyura and the Macroura ; and, as constantly occurs 

 where nature passes from one type of lurm to another, we find amongst 

 (1 ese animals some of ihe most strikini; anunialies which occur in the 



^l^gj hence the name Aiionioura, or anomalous-tailed Crabs — 



\-liiili arc divided by M. Edwariis into two primary seciions or frtmi- 

 I et — 1. The Aptcrura, or those destitute of a terminal 8«-immeret, 

 iLicludinff the Dromicns, Homolieiis, Raiiiniens, and Pactulieust and. 



■f moveahle nppenflai;es 



2, The Pterye-ura, or those which have a pa 

 at the extremity of the tail, iiiciudiii(,' the Pnreellanicns, Hi|)pic 

 and Pai^uriejis. Tlius il will appear that the former section is uk 

 analojious lo the Brachyura, and the latter to the Rlaeroora.] 



t With the exception of the anterior pair, these Appendages i 

 either rudimental nr obsolete in the males,— a peculiarity which i 

 curs also in the Galathoea;, Scyllari, and Piilinuri. We may also ( 

 serve, that in these three genera, the swimmerets at (he extremity 

 the body are more slender, or nearly membrano'is, nt the poster, 

 mor^'in. In this section, as in Galatheca, the portion of the ihor 

 which supports the hind pair of leys forms a sort of peduncle, whvn 

 this pair of legs appearB to be attached to the taiL 



E E 



