1880.] MR. O. THOMAS ON MAMMALS FROM ECUADOR. 401 



review of the Neotropical Squirrels^ says, in reference to the dis- 

 tinctness of that species from >S. cestuans, " That connecting links 

 may yet be found seems very probable ; but I have not been able to 

 find sucli in the very large series I have examined, and am conse- 

 quently compelled to keep them provisionally distinct." Now these 

 two lutac specimens seem to me to be just such intermediate specimens 

 as Mr. Alston refers to. S. griseogenys is separated from S. cBstuans 

 by having its belly and the tips of the tail-hairs of a rich orange or 

 rufous, while the same parts in S. cestuans are white or pale yellow, 

 and also by its larger size. One of the Intac specimens is very like 

 typical S. cestuans, having the belly white and the tail-hairs tipped 

 with yellow ; but it is considerably larger than the average size of 

 that species, and on the sides of the chest and the middle of the tail 

 there is a tendency to a reddish coloration. The specimens col- 

 lected by Mr. Fraser at Gualaquiza and referred to by Mr. Tomes'", 

 seem to have been somewhat of this character ; those from Palla- 

 tanga, on the other hand, were typical S. griseogenys^. The other 

 specimen is far more hke this latter species, as all along the sides of 

 the belly the fur is a rich orange-rufous, and the tips of the tail-hairs 

 are of the same colour ; so that this specimen only differs from S. gri- 

 seogenys by having the throat and centre of the belly white, as in 

 5'. astuans. Tiie Balzar specimen is a typical -S. griseogenys. 



It was quite to be expected that the links between these two spe- 

 cies would be found in Ecuador, as iS. cestuans ranges over Bolivia, 

 Eastern Peru, Brazil, and Guiana, while S. griseogenys is found in 

 (yolombia, Venezuela, and Central America. 



jS. griseogenys may still be considered a very well marked variety, 

 and should stand as S. astuans, var. hojfmanni. Dr. Peters having 

 described it under this varietal name in 18(>3^ while Dr. Gray's 

 S. griseogenys dates only from 1867". 



28. CcELOGENYS PACA, Linn. 

 A single skull, Sarayacu. 



29. HOLOCHILUS, sp. 



An albino Rat from the Balzar Mountains is referable to this genus ; 

 but its size and proportions do not agree with those of any of the 

 hitherto described species of Holochilus. Without seeing normally 

 coloured individuals, however, I do not feel justified in describing it 

 as new, as there are numerous species of South-American so-called 

 Mus and Hesperomys which have been described merely on external 

 characters, without reference to the skull, by which alone the correct 

 genus of a murine animal can be determined. 



1 P. Z. S. 1878, p. 667. "" P. Z. S. 1858, p. 547. 



3 P. Z. S. 1860, p. 213. 



^ Moiiatsb. Ak. Berl. 1863, p. 654. Mr. J. A. Alien, provisionally accepting 

 the distinction of the form in his paper (Bull. U.S. Geol. & Geogr. Surv. iv. 

 p. 885), called it Sciurus Jwffmanni, Ptrs 



' Ann. & Mag, N. H. aeu. 3, xs. p, 419. 



