DECAPODA. 



417 



Trilie A [Jschhopoda, Westw.]. — Those which, in the proportions, forms, and uses of the feet, the 

 anterior, or at least tlie second, pair being cheliferous, and which carrying their eggs beneath tlicir 

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

 fisli, r»;awns, and Shrimps. Divisible into fom- sections: — 1. Anomala; 2. Locustcc; 3. Astacini; 4. 

 Carides. 



Tribe B ISchizopoda, Latr.]. — Those which have the legs slender and filamentous, accopapanied by 

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

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

 Shrimps.]* 



The first section [of the tribe Aschizopodii], or the Anomala. — The 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 legs.f The lateral swimming-pieces at the extremity of the tail, or the parts which 

 represent them, are thrown back 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 Macroura of the following 

 sections. [Two subsections, Hippides and Paguriens.] 



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

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

 six or four following legs terminate in a swimming-plate. 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 the 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 antennae are very pilose 

 and ciliated, the lateral at first approaching the intermediate, and then being bent outwards. 



Albunea, Fabr., comprises a single species from the Indian Seas {Cancer Spniiista, Linn.) 

 [a singularly formed animal], with long, setaceous, intermediate antennae; the carapax flat, 

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

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

 Hippa, Fabr., Emerita, Gronovius, has the antennae short, the intermediate with two fila- 

 A, v'l Y ments longer than the external ; the two fore-legs terminated by a very compressed claw, 



^^t kC^ without fingers ; 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 some other particulars. Type, R. 

 testudinarius, 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 



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 Cancelli) 



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 filiform villose 



branches. The three terminal segments are suddenly narrowed. 



Birgus, Leach, has the tail solid, suborbicular, with two rows of plate-like 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 



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



( )n 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. 



Fi-tf. 5. — Remipes testu- 



♦ 'It is lierc proper to observe, that in the recent arrangements of 

 IVIUue Kdwards and M'Leay, the seventh and last section, Notopoda, 

 of l.atreille*s arrangement of the Brachynra, and liis first section of 



the Ma 



of tlie thri 



Aitomala, constitute on 

 of the Dccapoda, forming, as may be readily pei 

 between the Brachyura and the Macroura; and, 

 where nature passes from one type of form to anot 

 these animals some of the most striking anomalie 

 class — hence the name Anomoura, or anomal 

 which are divided by M. Kdwards into iwo prim 

 lies-—!. The Apterura, or those destitute of a t 

 including the Dromicns, Hoinoliens, RaniiiieiiN, i 



primary divisions 

 ■ived, the passage 



constantly occurs 

 r, we find amongst 



vhich oc( 

 iS'tailed 



ur in the 

 Crabs — 

 or fanii- 



2. The Pterygura, or those which have a pair of moveable appendages 

 at the extremity of the tail, including the Porcellanicns, Hippiens, 

 and Paguriens. Thus it will appear that the former section is more 

 analogous to the Brachyura, and the latter to the Macroura.] 



t With the exception of the anterior pair, these appendages are 

 cither rudimental or obsolete in the males,— a peculiarity whicli oc- 

 curs also in the (ialatha-ic, Scyllari, and Palinuri. We mav also ob 

 serve, that in these three genera, the swimmercts at the extremity of 

 the body are more slender, or nearly membranous, at the posterior 

 margin. In this section, as in Galatha;a, the portion of the thorax 



t, I which supports the hind pair of legs forms a sort of peduncle, whence 



I, I this pair of tegs appears to bo attached to the tail. 



K E 



