from the Neotropical Region. 311 



Skull : basal length 21 ; basilar length 19*2 ; greatest 

 zygomatic breadth 13'2 ; nasals 10*2 x 3"8 ; interorbital 

 breadth 7*0 ; intertemporal breadth 6*2 ; breadth across brain- 

 case above auditory meatus 13*1 ; palate length from 

 henselion 10; diastema b'S; palatal foramina 4"7 x 2*4 ; 

 length of upper molar series 4*1. Lower jaw: condyle to 

 incisor-tip 15'4. 



This most interesting and peculiar little animal has a certain 

 superficial resemblance to Acodon nigrita^ Licht., found by 

 Dr. Goeldi at the same time and place, but is readily distin- 

 guished by its many essential differences. It is evidently a 

 regular burrower, and probably passes a more mole-like life 

 than any other Sigmodont as yet described. 



Ctenomys Perrensi, sp. n. 



Size of and most nearly allied to G. torquatus, Licht. 

 General colour dark buff or clay-colour, heavily mixed with 

 black along the median line of the face and back. From eye 

 to ear and below the latter a rather lighter patch, succeeded 

 below again by the brownish cheeks. Under surface from 

 throat to belly rich buff (" ochraceous-buff " of Ridgway), 

 but patches on the axillae and groins are pure sharply con- 

 trasting white. Upper surface of hands and feet thinly 

 haired, white. 



Skull short, broad, and rounded, not heavily ridged. 

 Zygomatic decidedly exceeding the posterior breadth. Nasals 

 short, tapering backwards, unusually little, broad and trun- 

 cated behind. Interorbital region short and very broad, the 

 postorbital processes and ledges little developed. Fronto- 

 parietal suture nearly directly transverse, little bowed back- 

 wards. Bullae small and little inflated, especially anteriorly. 

 Incisors more curved backwards terminally, and therefore 

 forming a larger arc of a smaller circle than usual. 



Dimensions of the type (an adult male, measured by 

 collector) : — 



Head and body 200 millim. ; tail 67 ; hind foot 31, with 

 claw (dried) 37. 



Skull : basal length 43'5 ; basilar length from henselion 

 40*7 ; zygomatic breadth 30 ; posterior breadth on bullse 23 ; 

 ditto on projecting lip of meatus 27'3 ; least breadth behind 

 zygomata 193; nasals 16*2 x 7*6 ; interorbital breadth 116; 

 length of frontals in middle line 13 ; palate length from 

 henselion 21*3 ; diastema 12'9; tip of incisor to alveolus of 

 Pii 14*9. Lower jaw : back of condylar process to tip of 

 incisors 35 ; greatest breadth 35*8. 



22* 



