the Species of the Geims Oavia. 153 



Cavi'a guianrt', Tlioa. 



C porcellus yidame, Thos. Ann. & Ma^. Nat. Hist. (7) viii. p. 152 

 (1901); 



and ill Venezuela 



" Cavia porcellus venezueics," All. Bull. Am. Mus. xxx. p."250X1911), 



whose distinction from r/viance appears most doubtful. 



As regards (jahuue, the original statements about its 

 characters were largely influenced by tlie fact that at that 

 date the few available Brazilian specimens (included both 

 aperea and what we now know to be the quite distinct 

 s\)ec\eii fulgida. As a matter of fact, guiatm has practically 

 the same colour as the real aperea, but is distinguished by 

 its smaller size, the largest of three full-grown siiells only 

 measuring 63 mm. in length*, with length of bulla f 

 J 1*8 mm. and upper tooth-row 14. The skull is pro- 

 portionately rather broadly built, with unusually developed 

 postorbital projecting ledges. 



Specimens are in the British Museum from the Kannku 

 Mountains, Berbice, and the Moon Mountains, all in Briiish 

 Guiana. 



Putting aside the Cavia porcellus of Linnaiu.«, based on 

 the Cavia cobnya of Marcgrave, the domesticated guinea- 

 pig, to which the name should be restricted, we next have 



Cavia aperea, Erxl. 



Cavia aperea, Erxl. Mamni. p. 348 (1777) (based on the " Anerea " of 



INlarcgrave, Bras. p. 228, 1048). 

 Ancema hilaria, Geoff. N. H. Mamm. (fol.) ii. text to pi. 282 (1820) 

 Cavia leucopxjya, Brandt, Mem. Ac. Petersb. 1835, p. 43(3, pi. ^\\. 



Size largest of the genus. General colour grizzled 

 l)rownish grey, not the clearer or more olivaceous grey of 

 the Argentine forms. Below dull whitish or drabby whi'tish 

 a clear white spot generally present on the middle line of the 

 chest just behind the brown collar. 



The largest of the available skulls measures no less tl an 

 73 mm. in total length, while the average of half a dozen 

 from Minas Geraes and Sao Paulo is 68-7 mm. in total length 

 bulla 11-9, tooth-row 15-5. The hiud foot in adults vanes 

 Irom 45 to 50 mm. 



* The skull-length is here always taljen from the tip of the nasals and 

 may sometimes be slightly exceeded by a slanting length from occipital 

 to gnathion. ^ 



t Measured from the notch in front of the paroccipital process directly 

 forwards parallel with the axis of the skull, not to the autero-interual 

 angle, which ends in an irregular poiut. 



