272 Mr. 0. Thomas on 



Hab. Waikthlatingmayalwa, Northern Chaco of Paraguay, 

 May 10, 1897. 



Type B.M. no. 98. 5. 14. 4. Collected and presented by 

 Mr. J. Grali am Kerr. 



Lengua native name " Pom65." 



Another specimen of this species, collected on the 31st of 

 May, 1897, at Puerto 14 de Mayo, in the Department of 

 Bahia Negra, Northern Chaco, by Dr. Boggiani, has been 

 submitted to me for determination by Dr. Gestro, of the 

 Genoa Museum. 



For comparison with A. lenguarum I have had a small 

 series of modern skins of A. obscurus, collected by myself in 

 May 1896 at Colon, near Montevideo, where I found it very 

 common, living in company with A. arenicola in the long 

 grass. 



Dasyprocta aguti and the Species allied to it. 



All the red- and yellow-rumped Agutis have hitherto been 

 lumped together under the above name, apparently without 

 much examination, for the most superficial comparison shows 

 that those at least of Guiana and Brazil are different from 

 each other, not to mention that other forms may prove to 

 exist. 



But the fixing of Linnaeus's " Mus aguti" on to one or 

 other of these animals has proved a matter of much difficulty. 

 In his original description * he refers to Brisson, Ray, 

 Marcgrave, Pison, and Johnston. Tracing these notices 

 back, they prove all to depend on the account of an animal 

 given at about the same time by Marcgrave and Pison, but 

 actually published first by the former f. In these accounts 

 the animal is distinctly stated to be Brazilian, and in Marc- 

 grave's geographical work + Brazil is strictly limited to a 

 country corresponding very nearly to modern Brazil, and does 

 not therefore include Guiana. In spite, therefore, of Linnaeus's 

 mention of " Surinam, Guiana," after Brazil, I would propose 

 to assign u Mus aguti" to the true Brazilian species. More- 

 over, the " abdomine favescente " mentioned in all the descrip- 

 tions, including Linnseus's, is alone applicable to the latter 

 animal, and might be thought by itself to settle the question, 

 even if the body-colour is rather yellow than " rufo- 

 fuscescentibus." 



* Syst. Nat. (12) p. 80 (1766). 



t Hist. Nat. Brasil. p. 224 (1648). 



X 'Tractatus Topographicus Brasilia),' p. 5 (1658). 



