1876.] Mil. E. R. ALSTON ON THE GENUS DASYPUOCTA. 347 



sportsmen who have had ample opportunities of studying the habits 

 of the Hazel Grouse, it is always monogamous, and that when 

 paired tlie pair remain strictly faithful to each other. Therefore I 

 have never heard of a Hazel cock having been seen at a " lek " of 

 the Black Grouse, though the male Willow Grouse has been known 

 to attend there, and to take ample advantage of his opportunities. 

 1 can only surmise that the present hybrid has been the result of a 

 Hazel cock which had failed in finding a mate, having paired with 

 some Grey Hen met with during his solitary wanderings. 



8. On the Genus Dasyprocta; with Description of a New- 

 Species. By Edward R. Alston, F.L.S., E.G.S., F.Z.S. 



[Eeceived March 11, 1876.] 

 (Plate XXIX.) 



My attention has been lately turned to the Mammals of Central 

 America ; and I have hence been led to review all the known species 

 oith^ ^ex\m Dusijprocta, concerning the characters and distribution 

 of which a good deal of confusion has existed. Through the kind- 

 ness of Mr. Sclater and Dr. Gunther I have been enabled to com- 

 pare the skins of a number of Agoutis which have died from time to 

 time in the Society's Gardens with the specimens in the British 

 Museum, and believe that I am now able to arrange the various 

 forms with some approach to general correctness. 



The range of the genus Dasyprocta extends throughout a coa- 

 siderable part of the Neotropical Region, from the Antilles and 

 Mexico in the north to Brazil and Paraguay in the south. Within 

 these limits there exist a number of weil-nlarked but nearly allied 

 geographical races, of which eight or nine appear to deserve specific 

 distinction. As might be expected in such closely related forms I 

 have been unable to find any constant cranial distinctions, and have 

 been compelled to depend on outward characters, of which I have 

 found the coloration of the long hairs of the rump to be the most 

 trustworthy. Owing (o the confusion which has existed as to some 

 ot these species, and to the carelessness of collectors and museum- 

 curators as to locality, it is very difficult to make out the exact dis- 

 tribution of the various races of Agouti ; but I have endeavoured to 

 note what little information we possess. 



The following, then, is the principal synonymy, with brief 

 diagnoses and habitats, of the various Agoutis, beginning with a well- 

 marked species, which appears never to have been described, and 

 which I propose to call : — 



1. Dasyprocta isthmica, sp. n. 



Fur ringed with black and yellow; rump black, more or less 

 washed with orange or yellow, the long hairs being black at the 

 base, scarcely annulatcd except close to the tips, wliich are broadly 



