164 Bulletin, Vanderhilt Marine Museum, Vol. II 



ridge, paralleled anteriorly by a deep sulcus, both of which curve from 

 the gastro-cardiac region out toward the base of the strong lateral 

 tooth. There are also two transverse tuberculated ridges on the gas- 

 tric region, the hinder one being much the shorter. The superior 

 orbital margin has two closed linear sinuses; there is one small 

 V-shaped sinus on the other half of the inferior orbital margin, which, 

 like the superior margin, is granulose and fringed with setae. The 

 infra-orbital angle is bluntly triangulate and is visible dorsally. The 

 outer distal angle of the peduncular joint of the antennae forms a 

 rounded, tooth-like node, situated in the orbital sinus. 



The chelipeds of the old males are much longer and stronger than 

 those of the female ; the merus has the upper surface pubescent, and 

 with a series of transverse, granulose rugae; the anterior margin is 

 armed with four, occasionally five, acute teeth; the carpus has three 

 longitudinal ridges on the upper surface, a very prominent acute tooth 

 at the inner angle, a minute tooth at the outer angle and another 

 tooth occurs at the outer propodal face, proximally and closely adja- 

 cent to the median carpal angle; the propodus has four longitudinal 

 ridges on the outer face and a fifth ridge on the upper margin which 

 terminates subdistally in an acute tooth ; the fingers are slender and 

 have the inner and outer faces grooved, the tips brown, curved, 

 crossing. 



The ambulatory legs are slender, with the meral, carpal and pro- 

 podal joints longitudinally ridges and with lines of pubescence be- 

 tween the ridges and fringing the anterior lateral margin. The dactyli 

 are long, grooved, acuminate. 



The natatory legs are stocky, the dactyl ovate-laminate. 



The external maxillipeds have the ischium subrectangular with a 

 slightly emarginate distal margin and an oblique longitudinal groove 

 on the outer face ; the merus is five-sixths as long as the ischium but 

 slenderer with the distal margin moderately rounded, the inner lat- 

 eral angle slightly excavate for the reception of the palp. 



Synonymy. — Achelous xantusi Stimpson, Ann. Lye. Nat. Hist. N. Y., 

 vol. 7, p. 222, 1860 (1862). 



Neptunus xantusii A. Milne Edwards, Arch. Mus. Nat. Hist., X, p. 

 429, 1860; Crust. Reg. Mex., p. 213, pi. 38, fig. 1, pi. 39, fig. 3, 

 1879. 



