534 MR. G. A. BOTJLENGKR ON THE [DeC. 4, 



Supraorbital edges evenly divergent, slightly beaded, but without 

 any marked postorbital thickening. Outer plate of anterior zygoma- 

 root short and weak, scarcely projected forwards. Anterior palatine 

 foramina long, reaching backwards just to the level of the front of 

 m.' Bullae rather larger than in 31. macleari, but far smaller than 

 in M. everetti. Lower jaw very thin and slender, contrasting very 

 markedly with M. macleari in this respect. 



Teeth small and weak, their structure as usual. Front of incisors 

 orange above, yellow below. 



This fine Rat cannot possibly be confounded with any other 

 known species of the genus'. Its size, peculiarly small and delicate 

 head, short anicolor tail, large hands and feet, and powerful 

 digging claws, separate it at once from any of its congeners. In 

 some respects it agrees with the description given long ago by Her- 

 mann of his Mus javanus^, but its brown underside and naked tail 

 prove that it is not really the same, and it is probable that Hermann's 

 description was merely founded on an unusually large specimen of 

 Mus decumanus. 



The presence of a second large Rat in such a small island as 

 Christmas Island is a very noteworthy fact, and recalls the state of 

 things existing in Guadalcanar, Solomon Islands, where two still 

 larger Rats, Mus imperator and M. rex, one terrestrial and fossorial, 

 and the other arboreal, live side by side in the same locality ^. 



Mr. Lister is to be congratulated on his discovery of this, the 

 largest member of the indigenous Mammalian fauna of Christmas 

 Island. It is unfortunate that he did not succeed in obtaining a 

 female specimen of it, as its mammary formula, perhaps the most 

 important character within the restricted genus Mus, therefore 

 remains still unknown. 



6. On the Reptiles of Christmas Island. 



By G. A. BoULENGER. 



[Eeceived October 15, 1888.] 



In addition to the three kinds of Reptiles* found on the island by 

 the ' Flying-Fish ' Expedition, examples of which were also obtained 

 by Mr. Lister, we have to record two new Lizards, viz. a Gecko, and 

 a Sciiik closely allied to the widely-distributed Jblepharus boutoni. 

 Thus, of the five species of Reptiles now known to inhabit Christmas 

 Island, four appear to be endemic, whilst the fifth, Gymnodactylus 



^ Mus infraluteiis, a species from Mount Kina Balu, North Borneo, described 

 by the present, author (Ann. & Mag. N. H. (6) ii. p. 409) since the above was 

 written, has a considerable superficial resemblance to M. nativitatis. Its tail, 

 however, is longer, and its skull is large and heavy, in due proportion to the 

 size of the body. 



2 Obs. Zool. p. 63 (1804). 



3 See supra, pp. 479-81. 



* Gymnodactylus marmoratus, Kuhl ; Lygosoma nativitatis, Blgr. ; and 

 Typhlops exocxti, Blgr. See P. Z. S. 1887, p. 516. 



