Order 1. 



DECAPODA. 



417 



Tribe A \_Aschizopoda, Westw.]. — Those which, in the proportions, forms, and uses of the feet, the 

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

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

 fish, Prawns, and Shrimps. Divisible into four sections: — 1. Anomala; 2. Locustae; 3. Astacini; 4. 

 Carides. 



Tribe B {^Schizopoda, 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 cheliferous, the eggs being carried beneath them, and not under the tail. [Opossum 

 Shrimps.]* 



The first section [of the tribe Aschizopoda], 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 Symnista, Linn.) 

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

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

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



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

 ments longer than the external ; the two fore-legs terminated by a very compressed claw, 

 without fingers ; the caraptax ovoid. Type, Cancer Emeritus, Linn. Indian Seas. 



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

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

 tettudinarius, 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 ; th3 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. 



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. 



Kg. 6. 



— Remipei testn- 

 dinanus. 



• ^,It is here proper to observe, that in the recent arrangements of 

 Milue F.dwards and M'Leay, the seventh and last section, Xotupoda, 

 of LatreiUe's arranttement of the Brachyura, and his first section of 

 the Macroura, Anomala, constitute one of the three primary divisions 

 of ihe Derapoda, forming, as may be readily perceived, the passage 

 between the Brachyura and the Macroura ; and, as constantly occurs 

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

 these animals some of the most striking anomalies n'liirh occur in the 

 cljufc — hence the name Anomoura, or anomalous-tailed Crabs — 

 which are divided by M. Edwards into two primary sections or fami- 

 lies- — 1. The Apterura, or those destitute of a terminal swimmeret, 

 including the Dromiens, Homoliens, Kaniiiiens, and Pactoliens; and, j 



2. The Ptery^ra, or those which have a pair of moveable appendages 

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

 and PagTirieiis. 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 

 either rudimental or obsolete in the males,— a peculiarity which oc- 

 curs also in the Galathsese, Scyllari, and P^Iiiiuri. We mav also oh 

 serve, that in these three genera, the swimnierets at the extremity ol 

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

 tnargin. In this section, as in Galathsea, the portion of the thorax 

 which supports the hind pair of legs forms a sort of peduncle, whenco 

 this pair of legs appears to be attached to the taiL 



2d 



