96 Mr. O. Thomas on small Mammals 
Royal Mail Steam Packet Company, who have assisted 
Mr. Kemp’s exploration in various very material ways. 
1. Holochilus vulpinus, Brants. 
3. 2789, 2813, 2824; 9. 2832, 2835. 
These and the specimens of Scapteromys tomentosus are 
practically topotypes of their respective species, as Sello was 
said to have collected both types on the Rio Uruguay, and 
the water of that river washes the lower (eastern) end of the 
islands of the Parana delta. 
2. Scapteromys tomentosus, Licht. 
&. 2815, 2817, 2818, 2819, 2826, 2829, 2842, 2843; 
9. 2804, 2814, 2828, 2831, 2834, 2839; and one ? in 
spirit. 
This series forms a very valuable addition to our collections, 
for although discovered on the R. Uruguay as long ago as 
1827, the species has never hitherto been sent home to us. 
Even the genus was only represented by the type of S. tu- 
midus, Waterh.,-from Maldonado (C. Darwin), and one skin, 
with imperfect skull, of the same species from Soriano, 
Uruguay (0. V. Aplin). 
Between the two species there does not seem to be any very 
important skull-character, and S. tomentosus would appear to 
be really a blackish delta representative of the greyer animal 
of Uruguay. 
3. Oryzomys delticola *, sp. n. 
3. 2845, 2846; 9. 2812. 
A middle-sized species, far larger than O. flavescens. 
Size and general characters very much as in O. longi- 
caudatus of Chili. Colour above lined buffy brown, the light 
rings on the hairs cinnamon-buff, but the general colour not 
quite like anything in Ridgway, though nearest to “ clay- 
colour’? or “ buckthorn-brown.” Sides, although a clearer 
tone than the back, not richly buffy. Under surface greyish 
white, tinged in one specimen with buffy ; the bases of the 
hairs slaty. Head greyer than back; ears, or at least the 
proectote, blackish. Hands and feet dull whitish. ‘Tail long, 
* This is not a hybrid word, as “delta,” although originally Greek, 
was incorporated into Latin as a declinable substantive. 
