THE SPECIES OF AEGLA — SCHJVUTT 515 



Remarks. — This species and A. ahtao are related. They are very 

 similar in appearance and in common have noticeably short antero- 

 lateral spines, relatively shorter than in other Aeglas, yet on 

 close examination there appear constant differences in the general 

 shape of the rostrum, its relative degree of flatness and excavation, 

 and distal attenuation. The anterolateral angle of the first hepatic 

 lobe of A. ahtao seems always to be acutely armed with a small 

 spinule or sharply pointed scale, larger than those generally arming 

 the lateral margin of the forepart of the carapace; in riolimayana 

 this angle is more or less rounded off, at most subacute, and scabrous 

 with scales no different from those generally arming the lateral 

 margins of the hepatic lobes. The anterior internal lobe of the carpus 

 of the chelipeds seems to be differently armed or spined in the two 

 species; there seems to be less nodulation of the inner ventral border 

 of the ischium of the chelipeds in A. riolimmjana than in A. ahtao. 

 The posterior more or less straight portion of the lateral grooves or 

 furrows of the areola are subparallel in A. ahtao; in A. riolimayana 

 they exhibit a decided convergence posteriorly; the straight sections 

 of the lateral boundaries of the areola are farther removed from the 

 lateral suture lines of the cardiac area at their posterior than at 

 their anterior ends (fig. 64) ; in A. ahtao the reverse is true (fig. 63). 



Distrihution. — All specimens of this species that I have seen are 

 from the Rio Limay in the vicinity of Lago Nahuel Huapi or from 

 the lake itself, or from their immediate tributaries. In addition to 

 the type lot of five males, Mr. Titcomb obtained some 20 specimens, 

 males and females nearly equally divided, from the outlet of the lake, 

 November 15, 1903. Of these the largest and smallest males are, 

 respectively, 24 and about 9 mm. in length of carapace and rostrum 

 taken together, the largest and smallest females 20.5 and 10.0 mm., 

 respectively; two small males (8.5 and 14 mm.) from Arroyo de 

 Jones, tributary to Lake Nahuel Huapi; and another small male 

 (21 mm.) from "Victoria Island, Nahuel Huapi," November 29, 1903. 

 On November 22, 1926, R. C. Shannon collected one small male 

 (16.0 mm.) at Correntoso, north end of Lago Nahuel Huapi, which 

 he presented to the United States National Museum. Otherwise, I 

 have examined three small specimens belonging to the Museo Argen- 

 tino, two small females (19.0 and 20.0 mm.) from Lago Nahuel 

 Huapi, which had been purchased from Emilio Budin (MA.C.N. 

 No. 9679), and one male (20.0 mm., M.A.C.N. No. 8388), which 

 appears to be this species and which carries merely the designation 

 "Neuquen" [Territory ? ] . 



