470 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 91 



small specimen, determination doubtful), St. Lucia, River San Jose, 

 Rosario, from near Carmelo, Nueva Palmira, and Frey Bentos, Uru- 

 guay; and Arroyo El Gato, Guateguaychii, Entre Rios, Argentina. 

 One small lot examined (M. C. Z. No. 10478) was labeled Maldonado, 

 Brazil (I believe that this should be Maldonado, Uruguay). 



AEG LA PR ADO, new species 

 Figures 48, 49 ; Plate 26, A, B 



Description. — A small to moderate-sized species. One of the larg- 

 est specimens I have seen measures about 25.5 mm. in length of 

 carapace and rostrum taken together. 



Carapace usually very convex, more so than in any nearly related 

 species; front fairly wide, narrower than in A. platensis. Rostrum 

 sharp, spinelike, ridge-roofed, exceeding eyes by at least twice the 

 length of the cornea ; the rostral carina is furnished with several lon- 

 gitudinal rows of irregularly placed, tiny corneous scales ; the carina 

 is continued backward past the anterior margins of the protogastric 

 lobes, at the level of which it widens out to form a low, blunt ridge 

 that may be more or less readily traced to the posterior margin of the 

 carapace; it is interrupted only by the cervical groove; this ridging 

 or transverse angling of the median line is not so prominently devel- 

 oped in all the specimens at hand, yet it is a conspicuous feature in 

 a very considerable number of the larger representatives of the species. 

 Though otherwise quite distinct this was the first species I personally 

 encountered in South America that had any real resemblance to 

 Nicolet's prominently keeled Chilean A. denticulata. 



Epigastric prominences are low to obsolescent swellings; anterior 

 margins of protogastric lobes sharply acute-angled, apex raised up and 

 almost small-tuberculiform, more prominently so in the smaller than 

 in the larger specimens. 



Orbits of good size, much larger than extra-orbital sinuses, which 

 are relatively moderate to small in size; orbital spine small, standing 

 fairly close to anterolateral spine. 



Anterolateral spines well-developed, reaching not quite to middle 

 of cornea. All three hepatic lobes well marked and corneous spined, 

 and each well set off from the others, so that the lateral margin of 

 the anterior portion of the carapace narrows stepwise from the cervi- 

 cal groove to the anterolateral spine. 



Hands very swollen looking, more or less broadly ovate. Movable 

 finger with a plainly marked, generally small-spined lobe on outer 

 margin near base. No particular crest developed on inner margin of 

 palm, and no such posterior angle or "heel" as in A. platensis; how- 

 ever, there is a noticeable spine or two (sometimes more, and then 



