418 



CRUSTACEA. 



The best known species (Cancer latro, Linn.) inhabits the Isle of France; and, according to a native tradition, 

 it feeds upon the fruit of the cocoa-nut, making its excursions during the night. [It is of large size, and is called 

 the Purse Crab. Mr. Cuming found it in abundance in Lord Hood's Island in the Pacific, living at the roots of 

 trees. Messrs. Quoy and Gaimard fed this species for many months on cocoa-nuts ; and Mr. Cuming discovered 

 that it climbs the Platanus odoratissima, to feed upon the small nuts of that tree.] 



In the Hermit Crabs (Pagurus, Fabr.), the four hind-legs are much smaller than the preceding, with the claws 

 covered with small tubercles. The tail is soft, long, cylindrical, narrowed at the tip, and only furnished with one 

 row of filiform, oviferous appendages. The thorax is ovoid or oblong. 



With the exception of some superficially-known species which live in sponges, serpulae, alcyons, &c, all the 

 others live in univalve shells, of which they close the mouth with their fore-legs and one of their claws, which is 

 larger than the others. It is stated that the females deposit their eggs two or three times in a year. 



[The manoeuvres of the native species, when they have outgrown their habitations, are quite ludicrous. Crawling 

 slowly along the line of empty shells, &c, left by the last wave, and unwilling to part with their now incom- 

 modious domicile until another is obtained, they carefully examine, one by one, the shells which lie in their way, 

 slipping their tails out of the old house into the new one, and again betaking themselves to the old one, if this 

 should not suit. In this manner they proceed until they have found a habitation to their liking. They feed upon 

 dead fish, and all kinds of garbage thrown on the shore ; and, when alarmed, they draw themselves closely into 

 the shell, closing the aperture so firmly, by placing their claws over the entrance, that it is next to impossible to 

 extract them without breaking the shell to pieces.] 



Some species, forming the subgenus Caenobita, Latr., are distinguished by the antennae stretched forward, the 

 intermediate pair being nearly as long as the lateral ones ; the thorax ovoid, conical, narrow, elongated, and very 

 much compressed at the sides. These lodge in land-shells on the rocks of the coasts, rolling down, with their 

 houses, in moments of danger. The other species, forming the most numerous subgenus, Pagurus, have the inter- 

 mediate antennae short and bent, with two short filaments. The front division of the thorax is square, or reversed 

 triangular. 



Cancer Bernhardus, Linn. (Pagurus strcblonyx. Leach), is very common on the coasts throughout Europe. It is 

 of a moderate size. Its two fore-legs are armed with points, with the claws nearly heart-shaped, that on the right- 

 hand side being the largest. Pag. Faujasii, Desmarest, a fossil species, approaches it very closely. 



Another species from the Mediterranean ditfers from the rest in many characters, and forms the subgenus 

 Prophylax, Latr. The tail is coriaceous, linear, and only curved at the tip ; and it has two rows of subabdominal 

 appendages. Probably the species which live in serpulae, alcyons, &c, such as Pagurus tubularis, Fabr., belong' 

 to this subgenus.* 



In all the subsequent Macroura, the two posterior legs alone are smaller than the preceding. The 

 subabdominal appendages are generally five pairs. The teguments are crustaceous. The lateral appen- 

 dages of the penultimate segments form a fan-like swimmeret in conjunction with the terminal one. 



The two following sections have a character in common, which separates them from the fourth, or 

 that of the Carides. The antennae are inserted [in a line] at the same height, the peduncle of the 

 lateral pair being never entirely covered by the scale when present. Often there are only four pairs of 

 the false subabdominal feet. The intermediate antennae are never terminated by two threads : they 

 are ordinarily shorter, or scarcely as long as their peduncle. The external plate of the swimmeret is 

 never transversely divided by a suture. 



The second section, Locust^e (so named from the Latin name Locusta, given to the most remark- 

 able species of this section by the Romans), have only four pairs of false legs. The extremity of the 

 swimmeret at the end of the tail is always nearly membranous, or less solid than the rest. The pe- 

 duncle of the intermediate antennae is always longer than the two terminal filaments, and moie or less 

 elbowed. The lateral pair have no basal scale, and sometimes they are even widened to a short but 

 greatly-dilated plate : sometimes they are very large, long, and much spined. The legs are all nearly 

 alike, and terminate in a point, — the anterior pair being but slightly larger than the following; their 

 penultimate joint, as well as that of the two posterior, is at most unidentate, but not so much so as to 

 form a perfectly didactyle hand. The carapax has no frontal elongation, like a pointed beak or lance. 



Scyllarus, Fabr., exhibits, in its lateral antennae, a perfectly isolated character, the terminal filament being 

 obsolete, and the basal joints greatly dilated transversely, forming a broad, flat, horizontal, and more, or less 

 toothed crest. The outer branch of the subabdominal appendages is terminated by a leaflet, but the inner one, in 

 some males only, appears in the form of a tooth. Leach separated them into the genera Scyllarus, Thenus, and 

 Ibacus, founded upon the proportions and forms of the thorax, the position of the eyes, and other parts. They 

 form burrows in argillaceous ground near the shores, in which they reside. Type, Scyllarus arctus, Linn. Scyl- 

 larus oequinoxialis, Fabr., is another species, the flesh of which is greatly esteemed [in the Mediterranean]. 



Palinurus, Fabr., have the lateral antennae large, setaceous, and set with sharp points. These Crustacea, called 

 by the Greeks Carabos, and by the Romans Locusta, are amongst the largest animals of the class. The [common] 



• I M. Milne Kdwards has published a valuable monograph upon the | Ntttnretta, which has been abstracted in vol. ii. of his Hist. Nat. 

 Pa^uridiE in vol. vi. of the new series of the Annates dea Sciences \ des Criistucta.] 



