iS. I. Smit/) on American Crustacea. 149 



Opisthocera Gilmanii, sp. nov. 



Plate V, figure 1, 



Male. The dorsal surface of the carapax is evenly convex in two 

 directions and nearly smooth, but very minutely granulated and con- 

 spicuously punctate with widely scattered punctures. There is no 

 indication of areolation except two minute lunate impressions in the 

 middle. The front has a smooth, revolute margin, which is continu- 

 ous with the upper margin of the orbits, and a distinct, submarginal 

 groove, which extends slightly along the inner portion of the supe- 

 rior orbital border. The orbits are large, open and shallow, only par- 

 tially filled by the ocular peduncles, and the inferior margin is sharp 

 and minutely denticulate. The antero-lateral margin is evenly con- 

 vex in outline, is broken by a small, oblique groove near the angle of 

 the orbit, and its edge is sharp and very slightly and obtusely dentic- 

 ulated anteriorly, but smooth posteriorly. The postero lateral mar- 

 gin is concave in outline and rounded. The inferior lateral regions 

 are naked and smooth. The labial border of the epistome is deeply 

 divided ; the lobes are very prominent, and neai'ly horizontally, the 

 median lobe being longest and its extremity triangular. 



The external maxillipeds are nearly smooth externally, but are 

 marked with a few scattei'ed punctations. 



The chelipeds are very unequal ; in both, the merus is triquetral, the 

 inferior angle rounded, but armed with a few small tubercles toward 

 the carpus, and the superior angles are obtuse and armed with numer- 

 ous tubercles, which are somewhat spiniform on the anterior angle ; 

 the carpus is smooth and rounded externally and has a prominent 

 spine on the inner margin. The basal portion of the propodus in the 

 larger hand, is very stout, the superior margin is quite high, but 

 rounded, and the inferior margin is armed with a few small tubercles 

 near the base, the fingers are long, rather slender, and irregularly 

 toothed within, and the dactylus is strongly curved so that the fingers 

 gape very widely. The smaller hand is quite slender, the fingers are 

 nearly cylindrical, very long, nearly straight, and but slightly gaping. 



The ambulatory legs are slender, naked and nearly smooth, the 

 meral segments are nai-row, and the dactyli are armed with three rows 

 of spines above and two below. 



The abdomen is widest at the third segment, and the first and sec- 

 ond segments are only slightly narrower; from the third segment, the 

 margins converge quite rapidly to the sixth, which is nearly twice as 

 broad as long and its lateral margins only slightly converging ; the 

 terminal segment is much broader than long and its extremity som 



