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



one above the other, with an elongate multiarticulated filament. 

 Mouth as in the ordinary Isopods ; mandibles not palpigerous ; 

 the two superior foot-jaws expanded into a well defined lower 

 lip, bearing palpi. 



Thorax separated into seven distinct segments, the three poste- 

 rior ones biarticulate near their lateral extremities ; each segment 

 giving origin to a pair of perfect legs, terminating with a strong 

 and slightly curved nail. 



Post-abdomen, or tail, divided into five segments, provided 

 with neither styles nor natatory appendages ; the under surfaces 

 each supporting a pair of branchial leaflets, longitudinally ar- 

 ranged, and covered by two biarticulated plates attached to the 

 outward edges of the last segment, closing over them much in the 

 manner of an ordinary bivalve shell. 



Species G. Antarctica. — Animal perfectly symmetrical, ovate, 

 elongate, and depressed. Teguments solid and calcareous. Color, 

 brown sepia. Length, from the insertion of the antennas, three 

 and a half inches ; width, one and three-quarters. 



Head traversely elliptical, terminating at its lateral and ante- 

 rior margin obtusely elevated, aud arched each way to its centre. 



Superior surface of the head ornamented with an imperfectly 

 sculptured "fleur-de-lis;" posterior portion obtusely elevated, 

 producing a marginal rim. Eyes small, reniform, indigo blue, 

 and placed near the lateral and anterior portion of the head, so 

 deeply impressed in the margin of the shell as to be easily dis- 

 tinguished from beneath. Inferior pair of antennce longer than 

 the superior, corresponding in length to the width of the head, 

 transversely, from spine to spine ; articulations four in number ; 

 last segment longest, the remaining three gradually diminishing 

 in length as they proceed to the place of insertion ; segments 

 triangulate, with angular projections on their surfaces ; edges of 

 the angles, and articulating extremities rigidly spined. Ter- 

 minating filament about the length of the basal articulations, 

 gradually attenuated until it diminishes to a finely pointed apex. 

 Superior antennce half the length of the inferior, three-jointed, 

 and terminating with an attenuated filament whose articulations 

 are indistinct ; segments angular, external one much the longest ; 

 extremities and angles likewise spined. Month with the labrurn 

 or upper lip hard and massive, resembling in form a reversed 

 heart. The mandibles are without palpi, stout and osseous, tip- 

 ped with a hard and black enamel. The maxillas are furnished 

 with the usual palpi. The lower lip, or superior foot-jaws when 

 united, sub-cordate; its palpi five-jointed, snugly embracing 

 the manducatory organs along their base, like a row of ciliated 

 leaflets. 



The thorax is composed of seven distinct segments, each one 

 being beautifully ornamented on its superior surface by an elon- 



