38 Mr. 0. Thomas on 



Semliki (Xeave). Type (a slightly immature specimen) from 

 the Upper "Welle. 



A young: example of this species shows the outer dark lines 

 more plainly than the adults. 



V. — Two new Tuco-tucos from Argentina. 

 By Oldfield Thomas. 



(Published by permission of tlie Trustees of the British Museum.) 



Ctenomys latro, sp. n. 



Near G. tucumanus. 



Size about as in tucumanus. General colour paler than the 

 peculiar dark fawn of tucumanus, more as in dorsalis, bu fry- 

 fawn on sides of head, on back, and on flanks, but the middle 

 area of the face and crown dark brown. Under surface 

 broadly washed with pale buffy (" light buff "), the throat 

 whiter, and a patch on the chest darker, near " avellaueous," 

 very like the belly-colour of C. tucumanus ; the colours of 

 upper and under surfaces rather sharply distinguished. Be- 

 hind each ear a light buffy patch runs downwards and back- 

 wards on the side of the neck. Tail dark brown on whole 

 breadth of upper surface, pale buffy on sides and below. 



Skull of about the same general shape as in C. tucumanus, 

 similarly low and flattened, though the brain-case is narrower. 

 Muzzle unusually broadened, owing to a peculiar thickening 

 of the bone outside the anterior half of the buried part of the 

 incisors. Isasals broad, abruptly and squarely truncated 

 behind, where they are considerably surpassed by the ends ot 

 the premaxillary processes, their sides forming straight con- 

 verging lines instead of the curves found in tucumanus. 

 Zygomata as widely expanded as in tucumanus, but distinctly 

 shorter antero-posteriorly ; a groove present along the upper 

 outer edge of the malar, not found in any of our five skulls of 

 tucumanus. Temporal ridges uniting to form a low median 

 sagittal crest, the ridges being quite separated in older 

 specimens of tucumanus. Supraoccipital smooth, without the 

 median ridge present in adult tucumanus. Bullae slightly 

 smaller than in tucumanus, but still smooth and well inflated, 

 not contracted as in Ct. pontifex. 



Incisors of the normal set and usual orange-colour. Molars 

 rather smaller and more delicate than in tucumanus, p 4 ex- 

 ceeding the molars in diagonal diameter rather less than is 



