110 Rathbun Synopsis of the American Species of Ethusa. 



Ethusa tenuipes Rathbun, new species. 



Closely allied to E. microphthalma Smith, but a much smaller species. 

 The shape of the carapace and the outline of the front are similar to those 

 of microphthalma ; the cardiac region is more elevated and surrounded by 

 a deeper groove. The eye-stalks are shorter than in microphthalma, the 

 first segment of the antenna reaching the cornea. 



The abdomen of the male is narrow ; the penultimate segment is slightly 

 narrower at its distal than its proximal end, and is shorter than its distal 

 width. The appendages of the first segment have a lanceolate, foliaceous 

 extremity, and sheathe the appendages of the second segment, which ex 

 tend far beyond those of the first, and have slender, converging tips. 



Chelipeds of the male very unequal, the right the larger. Right manus 

 with upper and lower margins convex. Dactyli of first and second ambu 

 latory legs more slender than in microphthalma, not vertically compressed, 

 and having four carinse, one above, one below, one anterior, and one 

 posterior; dactyli a little wider in a dorsal than in a horizontal view. 



Dimensions. <^: length, 6 mm.; width, 5.5. 



Type locality. Off Key West, Florida, station 2316, steamer 'Albatross,' 

 50 fathoms (U. S. Nat. Mus., No. 19855). 



Distribution. Also dredged at station 2388 in the Gulf of Mexico, off 

 the Delta of the Mississippi, 35 fathoms. 



