238 MR. OLDFIELD THOMAS ON THE MAMMALS [NoV, 3, 



its skull is very markedly larger, and its teetli even more so. 

 That is, however, the species with which it seems most nearly 

 allied. 



The presence of Rhipidomys roberti, like that of Neacvmys, 

 o-ives evidence of the affinity of the Cuyabd region of Matto Grosso 

 with the eastern slopes of the Andes, from which all the previous 

 members of this group have hitherto come. 



In naming this distinct species after Mr. Robert I wish to make 

 very special acknowledgment of the admirable work he has been 

 doing in South America during the last three years. His collec- 

 tions, perfectly prepared in spite of all the difficulties incidental 

 to a damp tropical climate and uncivilised surroundings, have 

 revolutionised the material available in the British Museum for 

 the study of the Mammals of Southern Brazil, Numbers of 

 species, previously kno-\vn to us only by the original descriptions 

 or by a few unmeasured, discoloured, or otherwise imperfect 

 specimens, are now represented by series of perfect skins with all 

 the details incidental to good modern work. And again, the 

 present collection, formed in a still more difficult country, links up 

 in the centre his own Eastern Brazilian material with that 

 obtained along the edges of the Andean chain by the late 

 Mr. Perry 0. Simons. 



19. Nectomys squamipes mattensis, subsp. n. 



S. 1005, 1019, 1025, 1037, 1050, 1203. 



$. 1031, 1033, 1048, 1109, 1131. 



External characters as in true squamipes and in garleppi ; 

 the latter also appears to grade into squamipes. 



Skull rather shorter and more rounded, less slender and 

 elongated than in true squamipes. Nasals as usual narrow and 

 elongate. Supraorbital edges with a marked raised bead, more 

 developed than in squamijjes, much more than in garleppi. Inter- 

 parietal small, narrow antero-posteriorly, its anterior edge 

 generally directly transverse. Palatal foramina long, widely 

 open, with a slight angular constriction at the junction of their 

 anterior and middle thirds. Opening of posterior nares wide, 

 the edge of the palate squarely transverse, the median pterygoid 

 fossa broader anteriorly than posteriorly, its breadth in front 

 greater than the length of m.^ Lateral pterygoid fossse propor- 

 tionally narrow and sharply pointed anteriorly. (In JV. squamipes 

 the median fossa is narrow anteriorly, broadening backwards, 

 with a rounded anterior border.) 



Dimensions of the type, measured in the flesh : — 



Head and body 200 mm. ; tail 200 ; hind foot (s. u.) 47 (extremes 

 44-47), (c. u.) 50 ; ear 24. 



Skull — greatest length 43 mm. ; basilar length 34*6 ; zygomatic 

 breadth 22"2 ; interorbital breadth 7; interparietal 3"4xll*5; 

 palate length 20*4 ; palatal foramina 7-5 x 3" 2 ; breadth of 

 posterior palatal fossa anteriorly 3"8 ; length of upper molar 

 series 6"3. 



