96 Mr. O. Thomas on small Mammals 



R.03'al Mail Steam Packet Compau}'', who have assisted 

 Mr. Kemp's exploration in various very material ways. 



1. Holocliilns vuljnnu^, Brants. 



rT. 2789, 2813, 2824 ; ? . 2832, 2835. 



These and the specimens of Scapteromi/<i tonientosus are 

 practically topotvpes of their respective species, as Sello was 

 said to have collected both types on the Rio Uiuguay, and 

 the water of that river waslies the lower (eastern) end of the 

 islands of the Parana delta. 



2. Scapteromys tomentosus, Licht. 



S. 2815, 2817, 2818, 2819, 2826, 2829, 2842, 2843; 

 ?. 2804, 2814, 2^2^, 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, Waterb., from Maldonado [C. Dartciii), 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 dellicola *, sp. n. 



(?. 2845,2846; ?. 2812. 



A middle-sized species, far larger than 0. flavescens. 



Size and general characters very much as in 0. longi- 

 caudatus of Chili. Colour above lined buffy brown, the light 

 rings on the hairs ciunamon-buflf, 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 slat3% 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. 



