94 



Caridka. 



Atya rivalis, sp. nov. Male. Carapax compressed, naked, and 

 entirely smooth, except the gastric region which is punctate with 

 shallow puncta. Rostrum short, median carina sharp, high, extending 

 to the acutely triangular tip and separated from the lateral carinas by 

 deep sulci ; lateral teeth right-angled, but not acute. Peduncle of the 

 antennula armed above with small spines ; inner flagellum shorter 

 than the carapax, but much longer than the outer. Antennal scale 

 considerably longer than the peduncle, narrow, ovate at the tip, the 

 outer margin straight and armed with a very slender spine ; flagellum 

 longer than the carapax. Legs of the first and second pairs equal 

 in size, smooth and naked, except the tips of the fingers ; meral 

 segments compressed and longitudinally sulcate. Legs of the third 

 pair much stouter than the others and the meral, carpal, and propodal 

 segments thickly beset with small squamiform tubercles ; propodus a 

 little longer than the carpus ; dactylus short, unguiform, the basal 

 portion slightly thickened and armed beneath with several minute 

 spines. Legs of the fourth pair much more slender and not so 

 strongly tuberculate, but the carpus armed with one, and the merus 

 with two or three spines beneath. Legs of the fifth pair still more 

 slender, the propodus proportionately longer, and the merus and carpus 

 spined beneath as in the fourth pair. Abdomen smooth and naked ; 

 lateral margins of the second, third, fourth, and fifth segments 

 truncate. Lamellae of the appendages of the sixth segment evenly 

 rounded at their extremities and projecting only slightly beyond the 

 terminal segment. Terminal segment narrow, the sides straight and 

 converging regularly to the truncate extremity, which is ciliated 

 and armed with minute spines; dorsal surface with a slight median 

 sulcus with lines of small aculei each side. Length from tip of rostrum 

 to extremity of abdomen, 40.6 mm - Length of carapax, from orbit to 

 middle of posterior margin, 13.2 ; from tip of rostrum to middle of 

 posterior margin, 15.6; breadth of carapax, 6.8; height of carapax, 

 8.4. Third thoracic legs, entire length, 27.5; merus 9.0; carpus, 

 3.6; propodus, 3.4; dactylus, 1.3. 



Fresh water streams, Polvon, Occidental Department, Nicaragua. 

 Six specimens. 



Atya tenella, sp. nov. Male. Carapax compressed, narrowed in 

 front, entirely naked, and smooth, or slightly punctate on the gastric 

 region. Rostrum longer than in the last species; terminal portion 

 acute, somewhat cleflexed, and with a sharp carina both above and 

 below; lateral teeth obtusely rounded. Peduncle of the antennula 

 unarmed, except a few weak, bristle-like spines at the articulation 



