374 CRUSTACEA. 



feet of male equal, hand hardly inflated, sulcate above. Abdomen 

 of male rather narrow, with the sides excavate. 



Plate 23, fig. 11 a, animal, enlarged one and a half diameters; 6, 

 outer maxilliped, ibid. ; c, male abdomen and sternum, ibid. 



Island of Tahiti, Society Group. 



Length and breadth of carapax of male, six lines. Colour, reddish 

 brown and grayish brown. The legs have much resemblance to those 

 of the planissimits, though shorter, and the carapax is not so regular 

 and distinct in its naked longitudinal lines, the tomentose coat being 

 more general. The width of the front is equal to the distance from 

 its base to the tip of its first spines (counting from base) . The second 

 apical spines are shorter than in the planissimus. The less inflated 

 hand, sulcate above, and the absence of naked lines, as well as the 

 shorter form, are good characteristics. The second tooth or spine of 

 the antero-lateral margin rises just anterior to the third, and is mostly 

 concealed by it, being also very small, the apex of the second not 

 reaching as far forward as the apex of the third. 



A. ablrematus, DANA, Proc. Acad. Nat. Sci. Pkilad., 1851, v. 252. 



FAMILY IV. GECARCINID^E. 



THE Gecarcinidse pertain naturally to two groups or subfamilies, 

 one having the termination of the outer maxillipeds exposed as usual, 

 and the other having this part concealed beneath the second and third 

 segments. The subfamilies and genera are as follows : 



SUBFAM. 1. UCAIN^. Articulus maxillipedis externi 4tus apertus. 



1. Maxillipedes externi non hiantes. 

 Gf. 1. UCA, Leach. Articulus maxillipedis externi 4tus angulo 3tii extcrno insitus. 



