AMPIIIPODA. 4l7 



1. The Uroptera, Latr., having the head generally large, the antennse often short, and only two 

 in number in some, and the liody soft ; all the legs except the fifth pair simple, the anterior short or 

 small, and the tail either furnished at the tip with lateral swimmerets, or terminated by appendages or 



dilated points, bidcntate or furked at the extremity. They reside in the bodies of various Acalephce 

 or Medusa, Linn., and some other zoopliytes. 



t^ome,formiivi^ the genus P/(;7j/;»«(7, Lat., have only two very short and 2-jointect antennae. The fifth pair of 

 let^^s is by far the larf;-est, and terminated by a strou;^ didactyle claw. There are six ion^ slender appenda^-us at 

 the extremity of the body, c-ach terndnated by two points. There are probably various species, but \^liicli liave 

 not been described with sulhcient care. Type, Cancer sedentarius, Forskal, JPauu. Arab., found in the Mediter- 

 ranean, lodged in a membranous, transparent, bell-like ba^, probably the body of a Beroe. 



Others have four antennfe ; all the leg-s are sin)j:le, and the tail is furnL-ihed at each side of its extremity with a 

 plate, like a foliaceous swimmeret. 



Hj/peria, Latr., having the body thickened in front, the head large and almost entirely occupied by two oblong 

 eyes, somewhat notched at the inner mar2;in, two of the antenna; at least half the lenf>;th of the body, with a ter- 

 minal multiarticu!ated filament. Type, Ca/iccr monoruloides, Montague, [found on the coa^t of Devonshii-e]. 



Phroshw, Risso, diftVr^; in having the antenna:; not longer than the head, and but few-jointeLl, the terminal Ula- 

 ment being conical. 



Dacffilocera, Latr., has the body not thickened in front, the head of moderate size. 



T/ifminfo, Guerin, has the third pair of foot-jaws terminated by a small didactyle claw ; the third pair of legs is 

 very much longer than the others. [Many additional subgenera have been recently proposed, belonging to the 

 Uroptera, especially by i\I. Edwards.] 



2. The second subsection, Gammarin.e, Latr., have always four antennae, the body covered ^vith 

 a coriaceous elastic tegument, generally compressed and arched ; the posterior extremity of the tail is 

 not furnished "with swimmerets, hut its ap])endages are in the form of cylinchical or conical styles. 

 Two at least of the four anterior legs are terminated by claws. 



The vesicular bags in those species in "which they have been observed (6'fl*»m(7/'H.5), are situated at 

 the external base of the legs, commencing with the second pair, and accompanied by a small plate. 

 Tbe pectoral scales enclosing the eggs are six in number. 



In the majority the four antennae, although occasionally varying inter se, are applied to the same purposes, and 

 have the same general structure : the inferior never being leg-like. 



lour, Latr., is an anomalous subgenus, founded upon a figure given by Montague, ( L/nn. Traits., vol. Lx. 3, 3, 4.) 

 The body is apparently 15-jointed, the joints being only indicated by lateral incisions ; the four antennae are very 

 short, the external longer than the two others ; the two anterior segments of the body are furnished in the female 

 "svith two elongated fleshy cirrhi, like oars; the legs are very short and hooked ; the six terminal segments are 

 ]irovided with lateral, fleshy, elongated, fasciculated appendages, simple in the male but branched in the female. 

 Type, Onucus (horaciciis, Montague, found beneath the carapax of CoUianassa subterranea, forming a tumour on 

 the sides of its body. Montague kept it alive for several days, having removed it from its native abode. The 

 females are always accompanied by the males, which retain themselves tirmly attached to the abdominal ap- 

 pendages of their partners by means of their strong hooks. In regard to its habits, therefore, this animal approaches 

 the parasitic Bopyrus. 



All the remaining Amphipods have the segments of the body distinct in their entire breadth, and are destitute 

 in both sexes of the long oar-like appendages found in lone. In some of these the moveable linger of the claw- 

 legs is formed of a single joint. 



Orrhrstia, Leach, and Tolitnis, Leach [comprising British species] have the upper antennje much shorter than 

 the inferior, whilst in the following they are not much shorter, [indeed often much longer. The tyi>e of the latter 

 f^enus is Tnlitni.s locuxia, which is very abundant on our shores, burrowing into the sand, and, unlike the majority 

 of the species, seldom entering the water.] In Aiylus, Leach, the upper antennse are nearly as long as the inferior, 

 the head is produced above into a snout, and none of the legs are cheliferous. Type, A. carinatua, Leach. The 

 typical genus Gammarus, Latr., is distinguished by the isolated character of the superior antennfe, having a short 

 bi-anch at the tip of the third joint, and the four fore-legs are in the form of small claws, with the moveable finger 

 folding on the under-side; Cancer pulcxisthe. type. [It is exceedingly abundant in fresh-water brooks, where 

 there is an accumulation of vegetable debris.] Various other genera, as MeUfn, Leach, M<j-ra, Leach, Amphitlwe, 

 Leach, Phcntsa, Leach, &c., have been established by Leach and M. Milne Edwards, founded upon variations in 

 their legs and claws. 



Leucothoe, Leach, has the moveable linger of the two fore-claws biarticulated. The same character also exists 

 in Cerapiis, Say, composed of a small species found on the sea-shore of the United States, near 'Z^s; harbour, 

 amongst the Seriulari^, and which receives its specific name, C. tubidaris, from residing in a small cylindrical 

 tube. [Dr. Templeton has described a small species of Crustacea from Mauritius in the Trans. Entom. ^Soc.,\o]. i. 

 rt. 189, under the WATne of Ccrapus abditus, which inhabits a little membranous tube, resembling in texture the 

 papyritious covering of wasps' nests. It is remarkable for wanting feet to the middle segment of its body. Its 

 movements are very singular.] 



