3gQ CRUSTACEA. 



Nassau Bay, Tierra del Fuego, abundant. 



Length of carapax, four to five lines. Colour, mostly dark reddish 

 brown, somewhat clouded. Carapax transversely orbiculato-elliptical. 

 Upper surface of carapax smooth. Feet slender and very nearly 

 naked. Tarsus of eight posterior legs but little shorter than pre- 

 ceding joint and nearly straight, short hirsute within. Second and 

 third joints of outer maxillipeds nearly equal, surface pubescent. 

 Buccal area nearly square. 



Leucosia planata, Fabr., Bnt. Syst., Suppl., 350. 



Halicarcinus planatus, White, Ann. Mag. Nat. Hist., xviii. 178, 1846, pi. 2, f. 1. 



Hymenosoma Leachii, GrUERiN, Icon., pi. 10, f. 2, and Voy. de la Coquille, ii. 22. 



Hymenosoma tridentatum? Hombron and Jacquinot, Voy. au Pole Sud, pi. 5, 

 f. 27. This figure is referred to t\\e planatus by "White; but the form as represented, is 

 more transverse ; and as no description has yet been published, we feel still uncertain as 

 to its identity with the above. 



Halicarcinus pubescens. 



Carapax ovato-orbicularis, pone medium latior. Pedes longitudine 

 rnediocres, 8 postici laxe pubescentes. Abdomen maris angustum, fere 

 lineare, apice triangidatum. 



Carapax ovato-orbicular, broadest posterior to middle. Feet of me- 

 dium length, eight posterior lax pubescent. Abdomen of male 

 narrow, nearly linear, triangulate at apex. 



Plate 24, fig. 8, male, enlarged. 



From a depth of fifty fathoms, off Cape Blanco, the east coast of 

 Patagonia, where it was dredged up by Lieut. Case. It was found in 

 holes, or upon the surface of coral or stones. 



Length, one-tenth of an inch. The back is slightly concave, and 

 either side there are two small teeth (the anterior nearly obsolete), 

 situated, as usual in the genus, on the lateral surface, below the 

 margin. The sides of the male abdomen are for the most part parallel, 

 the last joint a nearly equilateral triangle. 



H. pubescens, Dana, Proc. Acad. Nat. Sci. Philad., 1851, v. 253. 



