Species 0/ Kcitiirotlon do. from Anicntlna. ill 



I say fourth species, because there is no doubt that Water- 

 liouse's ^4. cuvieri is the same as A. benneltii — so that with 

 A. murrai/i, WoUl.s., there are two in Chili, while !Sr. Budin 

 had previously discovered A. einerea at Casabindo, Jiijuy. 



I have pleasure in recognizing tSr. Budin's keenness in his 

 search for new animals by naming this most interesting 

 sprcies in his honour. 



B. The Scaptseomys of the Parana Delta. 



When giving an account oi: the mammals obtained on the 

 islands of the Parana delta by Mr. R. Kemp in 1917 *, I 

 assumed without very close enquiry that the interesting black 

 and white water-rat of the genus Scapteromys was referable 

 to S. tomentosns, based on Lichtensiein's Mus tO'inentosus'\ 

 from the Rio Uruguay, collected by Sellovv. 



But further consideration indicates that this is not the case. 



In tlie first place, the localities would appear to be by no 

 means so adjacent as 1 had supposed, for although the Rio 

 Uruguay runs out close to the Parana delta, Mus tomentosns 

 was said to have come from the " waldi":en Geofenden " of 

 that river — in other words, from the Upper Uruguay, where 

 alone the country is really forested, and where the fauna 

 would be appreciably different from that of the water-logged 

 Parana delta |. 



Then the delta animal, as suits its locality, is by colour, the 

 texture of its fur, and its known habits (.listinctly a water- 

 animal, while there is no indication of water-characteristics 

 in the coloration of tomentosns, nor has its tail got the 

 swimming fringe below that occurs in the delta species. 



In size tomentosns would appear to exceed considerably 

 both tumidus and tlie delta form, as its hind foot, including 

 claws, is said to be 2 inches in length. 



In consequence, I jjropose to describe the delta Scap- 

 teroniT/s as 



Scapteromi/s aqnaticus, sp. n. 

 Size less than in S. tomentosns. Upper surface slaty 



* Ann. & Mag. Nat. IlUt. (8) xx. p. 96 (1917). 



t Darst. Siiuf,'. pi. xxx. fig. 1 (18.30). 



\ liutjii.it as this paper is in tlio pre.«8 Prof. Matschie informs me tliat 

 Sellow's collections were made near Malilonado, wliere <S. tmnidiia was 

 obtained by Darwin — a region laiinally very ditlbrent from the Parana 

 delta. He also gives mo some mea-suremeuts of tho type which are 

 confirmatory of the marked inferiority in size of 6'. uqnatwuB. 



