obtained on the Rio Jordao. 533 
compels me to differ from Dr. Winge’s conclusions about the 
Cavia of Brazil, and to agree with those of Lund, quoted 
above. Mr. Robert’s Rio Jord&o specimens clearly belong 
to a species larger and greyer than the ordinary ‘ Prea”’ of 
the coast regions, of which Mr. Robert sent home examples 
in his Cruzeiro and Piqueté collections. In the one case the 
basilar length is about 54-56 millim., and in the other about 
48-50, fully adult individuals only being considered. That 
the latter never reaches the size of the former is also con- 
firmed by Hensel’s statement that the largest skull obtained 
by him was only 50°6 millim. in basilar length. 
Lund observed this difference, and rightly basing his 
conclusions on Marcgrave’s measurement and description, 
allocated the name aperea to the larger form and renamed 
the smaller rufescens. As that of the first distinguisher of 
the two forms, this allocation must necessarily be followed. 
Now, however, that by the recognition of two wild forms 
the origin of the domestic guinea-pig (Cavia porcellus, Linn. 
S. N. (10) 1. p. 59, 1758, based on the Cavia cobaya of 
Marcgrave*) becomes doubtful, it would be better to restrict 
the name porcellus to the domesticated form only, using for 
each of the wild forms the names respectively based on them. 
Dr. Winget considered ‘ C. rufescens”’ to be merely the 
young of C. aperea, but he has not noticed the discrepancy 
in size between his specimens and those of Hensel and others. 
He has been good enough to give me some measurements of 
Lund’s specimens, which show that the latter undoubtedly 
obtained the large form now first collected for us by 
Mr. Robert. 
Brandt’s Cavia leucopyga is nearly certainly this species, 
presuming that he took “ C. aperea” in the usual and not in 
the revised sense. On the other hand, C. fulgida, Wagl. ft, | 
is no doubt very closely allied to C. rufescens. Indeed, had 
it not been expressly stated that it was from the Amazonian 
journey of Spix, I should have synonymized the two, tor its 
collector was also in the region inhabited by C. rufescens. 
The Paraguayan guinea-pig (the Aperea of Azara and 
* Bras. p. 224 (1648). This affords another instance of what I venture 
to think is the best way of getting at the primary reference in Linnzeus’s 
synonymies. Here Linneus first quotes his own ‘ Westgita Resa,’ 
p. 244 (misprinted 224), and there we find Ray alone quoted. In Ray 
the primary reference is to Marcgrave, and we thus vet at the origin of 
the name without confusing the discussion with Linnzeus’s subsidiary 
references to Aldrovandi, Johnston, Piso, Xe, 
+ E Mus. Lundii, Gnavere, p. 187 (1887). 
{ Isis, 1831, p. 512. 
