J. Eights on a Crustacean from the Antarctic Seas. 393 



gated and sub-conic insculptation, forming a series, whose pointed 

 apices almost unite along the longitudinal dorsal ridge. These 

 segments are finely bordered along their posterior articulating 

 edges by an elevated and continuous marginal rim, extending to 

 the lateral extremities of the shell. The cephalic depression is 

 likewise margined by an obtusely elevated border. Each seg- 

 ment of the thorax gives origin, beneath, to a pair of ponderous 

 angulated legs, composed of the ordinary parts. The three an- 

 terior pairs project themselves forward, and are closely com- 

 pressed upon the inferior surfaces of the three foremost seg- 

 ments ; -they are nionodactyle, with the nails incurved upon the 

 anterior edges of the rather largely inflated penultimate joint. 

 Each joint is furnished at its articulating extremity with rigid 

 spines ; the inner edges of the penultimate joint, together with 

 those of the three adjoining, are provided with a double row of 

 tufted cilise, disposed diagonally, and much resembling in appear- 

 ance the arrangement of hairs in an ordinary brush. The four 

 posterior pairs of legs are directed backwards, strongly triangu- 

 late, stout and ponderous, terminating by a slightly curved nail ; 

 their length is nearly equal, but they gradually increase in thick- 

 ness as they recede toward the tail. The basal joints are large 

 and inflated ; the remainder regularly angulate. The extremi- 

 ties of the articulating joints, and edges of the two inferior an- 

 gles, are each provided with a series of tufted and rigid spines. 



The post-abdomen is composed of five segments. The four an- 

 terior ones are much smaller than those which constitute the 

 thorax, but greatly resemble them in form, being ornamented on 

 their superior surfaces with similar insculptations, though but 

 slightly defined. Each of these segments is provided beneath 

 with a pair of articulated pedicels, which furnish a support to 

 the bifoliated branchial leaflets. These leaflets are arranged 

 longitudinally one upon the other, and are entirely concealed by 

 the biarticulated plates of the caudal segment ; they are sub- 

 oviate and elongate : the outer ones smaller than those which 

 they cover, and are nearly surrounded by a fringed cilia, most 

 conspicuously developed along their inner margins. The second 

 pair are each supplied with an elongated style, extending almost 

 to the termination of the caudal segment. The terminating seg- 

 ment is large and triangular, giving attachment to the biarticu- 

 lated plates at a single point on its outer margins near the base, 

 which enables the animal to close them together in a line along 

 its centre beneath. These plates are about the length of the seg- 

 ment, and of a triangulate form, each one having near its ter- 

 mination a small oval articulation. The segment and marginal 

 plates are slightly inflated along their external edges, producing 

 an obtusely elevated border. 



SECOND SERIES, VOL. XXII, NO. 66. — NOV., 1856. 



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