472 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 91 



smaller spines) in line on the inner margin of the palm a little 

 behind its anterior border; outer margin of hand somewhat small- 

 spinulose, occasionally with a larger spinule or spine. 



Anterior internal lobe or angle of carpus of cheliped forming a 

 stout, acute, conical spine. Upper margin of merus with a straight, 

 longitudinal row of sharp spines, no inward turn at anterior end 

 as in A. uruguayana; anterior margin of merus scabrous or small 

 denticulate. Ischium below on inner margin armed with a well- 

 developed sharp spine at anterior end, a prominent feature even 

 in quite small specimens; at posterior end a low conical tubercle or 

 nodule, often with acute corneous tip (in only one of well-developed 

 males was there a fairly sharp spine at the posterior end of the 

 ischial border in addition to the much stronger spine at the anterior 

 end). 



The first ambulatory merus has a spine of fair size developed on 

 the posterior ventral margin at about the level of the proximal margin 

 of the articulating membrane, besides the smaller spine at the distal 

 end of this same margin. With respect to this ventral meral spine, 

 A. prado reveals kinship to A. parana and A. sanlorenzo^ though quite 

 different from them in a number of other respects, particularly in its 

 smaller extraorbital sinuses, and therefore only moderately wide 

 front. 



Anterior dorsal angle of epimeron of second (in lateral view, ap- 

 parent first) abdominal somite spined, anteroventral border almost 

 straight to very slightly concave, ventral angle rounded off- 

 Sternal plate between chelipeds carries a median, corneous, spine- 

 tipped, conical tubercle; even in very small specimens this sternal 

 spine is of good size, well formed, and sharply acuminate. 



Eolotype. — One of the larger males of a sizeable lot of specimens, 

 U.S.N.M. No. 80017, collected in a small tributary of the Arroyo 

 Miguelete in the Prado, Montevideo, by the late Dr. Juan Tremoleras 

 and myself, December 1, 1925. This specimen, the second largest 

 male, is 25 mm. in length of carapace and rostrum taken together ; the 

 largest male, is 25.5 mm., the largest female 21 mm. long; included 

 in the material are a considerable number of juveniles between 10 

 and 15 mm. long. These Aeglas were plentiful under the grass and 

 vegetable debris that carpeted this very shallow stream, perhaps be- 

 cause of the numerous fragments of picnic lunch, bits of bread and 

 meat scraps, that had been thrown into the water. The water tem- 

 perature was between 28° and 29° C. 



Remarks. — This species and A. uruguayana are much alike in gen- 

 eral appearance, though very probably not in color in life. Most 

 specimens of the latter that I have seen are very light colored in 

 alcohol ; A. prado ^ on the other hand, is quite dark, even the specimens 

 that I collected 17 years ago. 



