430 



CRUSTACEyV. 



Leptomera, Latr. (Prafo, Leach), lias fourteen complete le^s (mcludms; tbe pair attached to the head), forniini.' 

 a regular series. In some of them {as in Gommanis pedattis, Miiller, formiijt,^ tlie type of the restricic(i reiius 

 Leptomera) all the l<;^s {except tbe two anterior) are furnished with a basal vesiric, wJiilist in the others (Cmct') 

 pedatifs, Montague, beiii- the type of Leach's I'roto) these appendages exist only at the base of the second and 

 four following; Ie;^^s. 



Nmipredia, Latr., has ten lej^s in a continuous series, the second and two following' pairs havino- a vesicular 

 body at the base. The typical species found on the French coast appears to me to be undescribed. 



CaprcUa. Lamarrk, have also only ten leirs, but the series is interrupted; the second and follouini,' 

 seg:uients being- destil iiti; of h^gs, Ijnt each i^ 

 furnished with two vesicular bodies. 'I'\ pe, •'^'juiUa 

 lohaia, Miiller. 



[Dr. Johnston has i>ublishcd a monograph of 

 the British species of this section in the eightli 

 volume of i\\eMaga:u}e of Ntitttral Histori/, and 

 Dr. Templeton aiid M. Guerin have respectively 

 described various additional species of this curi- 

 ous gruup.] 



The other LaMnndipoila, forming a second section (Ovalia, Latr.), have tlic body oval, with tlie seg- 

 ments transverse ; the terminal filament of the aiitei)n;e appears to 1)6 inarticiilateil. The legs are sliort, 

 or of only inoilrrate lengtli ; those of the second and third segments are imperfect, and terminated by a 

 long eyhndrical jdint without terminal hooks; they have at the l.)ase an elongated vesicular hddy. 

 These La-modipuda form tiie subgenus — 



(.''lamiis, Latr. {Lannuln. Leach), of which 1 have seen three species, all of which live 

 upon Cefacea, and of which the commonest {Oniscus Ceil, Linn.) is also found upon the 

 Mackerel. The lishermen call it the whale-louse. Another species, closely allied, was 

 broinrht home by Delalande, in his voyage to the Cape of Good Ilope. The tliird, which is 

 much smaller, is found upon the Cetacea of the Indian seas. 



[M. Roussel de VauzJ^me has published a very complete and interesting memoir upon 

 this singular genus in the Ainmli-s ihw Sciences Nafurellen for May, 1834, describing three 

 S])ecies living upon Whales nf the Southern Ocean, and also observed their resp(?etive 

 habits. Sometimes these creatures are so abundant on the Whales that the imli\iduals 

 they infest may be easily recognized at a considerable distance by the white colour these 

 Iiara:^ites impart to them. When removed, the surface of the body of the AVhale is found 

 to be d'^privedof its epidermis. C. orafis and prnrilis are stationary, being found in great 

 numbers agglomerated upon the corneous prominences of Bahcna mijsticetns. C. cn-oticux is, however, organ- 

 ized for its wandering habits, being of a slender form, and with larger legs, serving for prehension. The young 

 ones appear with fill the characters of their kind, only th^ head is rather large, and the suppo-ed branchial appen- 

 dages, instead of being long and slender, arc short and somewhat globose.] 



THE FIFTH ORDER OF CRUSTACEA, 

 iw)ponA,— 



Or the Polvgonata of Fabriciiis, (after the removal of the genus Monocuhis') is alUed to the 

 Loemodipoda in tlie absence of palpi to the mandibles, hut is se])iiratcd from them in other 

 respects. The t\Mi I'lU'c-lrgs are not attached to the head, but to a distinct segment, as are the 

 I'oUowmir feet. Tliese limljs are ahvajs fourteen in nund)er, luioked at the tip, ivithout any 

 vcsicidar apiieinhige at the base. The \nnk'r-side of the tail is furnislicd M'ith very distinct 

 ai)])endages, in the form of jilates or vesicular bags, of which the two anterior and exterior 

 ordinarily cover, either entirely or for the most part, the others. The body is generally 

 Hattened, or broader than deep. The mouth is composed of the same pieces as in the ju'c- 

 ceding; (see the general remarks on the Malacostraca) ; but here, those which correspond with 

 the two superior foot-jaws of the I)eea|iods present, even more strongly than ni those 

 Crustacea, the appearance of a lower lip, terminated I)}' t\\o palpi. The intermediate ]):iir of 

 antenna; is obsolete in the terminal species in t!ie order, which are terrestrial in their habits, 

 and Aviiich [coiise(pieiitly] differ from the rest in res])ect to their respiratory apparatus. 



'M. V. Audouin and M. Edwards have given (Arm. des Sciences Nat., 182/) some interesting 



