jS. I. Siiiith on American Crustacea. 121 



compressed and very long, the inner surfaces are smooth, and the pre- 

 hensile edges are very tuberculose and each is armed with a stout 

 tooth near the middle, the tooth on the dactylus being a little nearer 

 the base than the other; within these teeth the prehensile edges gape 

 widely leaving an ovate space, while beyond the teeth, the edges meet 

 and are nearly straight almost to the tips, which, however, are strongly 

 curved. The outer surface of the digital portion of the propodus is 

 nearly smooth but has a submarginal, crenulated crest below, and the 

 inferior margin is denticulate. The outer surface of the dactylus is 

 somewhat verrucose and the superior edge is denticulate and slightly 

 margined toward the base. 



In the smaller cheliped, the merus is slender and somewhat trique- 

 tral and the superior and exterior angles are sharp and granulated. 

 The hand is very similar to that of G. heterophthalnms. 



"^riie ambulatory legs are stout and nearly naked and the meral seg- 

 ments are somewhat compressed and their edges shar]) and minutely 

 denticulate. 



The abdomen is broad, the basal segment is considerably shorter 

 til an the second and third, the edges approach each other somewhat 

 at the junction of fifth and sixth, and the terminal segment is nearly 

 twice as broad as long and its extremity is rounded. 



Five specimens give the following measurements : — 



I have examined a large number of specimens of this species col- 

 lected at Corinto, on the west coast of Nicaragua, by J. A. McNiel, 

 (Collection Peabody Academy of Science). 



There are three female specimens of Gelasimiis collected at the 

 same locality by Mr. McNiel, which probably belong to this species 

 although they differ quite remarkably from it. The carapax (Plate II, 

 figure 8) is not so much narrowed behind as in the males, the dorsal 

 surface is evenly convex and thickly covered with rounded granules, 

 which are quite coarse along the lateral borders, and the branchial 

 regions are not raised above the gastric and cordiac regions, and are 

 separated from them only by slight sulci. The sides of the carapax 

 are perfectly symmetrical, the anterior angles are prominent and sharp, 

 and the lateral margins are marked by sharp crests of bead-like 



