1900.] MUS SYLVATICUS AND ITS ALLIES. 421 



ligne mediane des flancs et des cotes du cou, d'un brun-roussatre 

 dore ; la tete est d'une teinte brune et les longues moustaches 

 sont d'un brun cendre. La couleur blanche de toutes les parties 

 inferieurs s'etend jusqu'a, la ligne mediane des flancs et des cotes 

 du cou ; les quatres extremites sont aussi d'un blanc pur." 



The skull is about equal in size to that of M. sylvaticus and 

 with an identical tooth-pattern ; the total length of skull of 

 no. 88.9.25.6 (damaged) is slightly over 24 mm. 



Distribution. Known only from Japan. 



General Remarks. The only specimens of this Mouse at my 

 disposal are nos. 88.9.25.6 aud 88.9.25.7, collected by Mr. H. 

 Pryer, and which bear on the labels the simple locality " Japan." 

 The latter is a female with the mammae arranged as in M. sylvati- 

 cus, and, since the general pattern of coloration and teeth, and 

 skull, where not damaged, also agree with that species, I can have 

 no hesitation in regarding this Mouse as very closely allied to 

 M. sylvaticus. The dimensions of the dried skins, however, seem 

 to show that the animals are considerably smaller than average 

 M. sylvaticus. 



Although Temminck gives no particulars as to the skull of his 

 M. argenteus, and although his figure of that species is a miserable 

 caricature of a dark brown M. muscuhts-like Mouse, with dark 

 feet, long tail, and light underside, his description, which, it will 

 be noted, contradicts his figure in several important respects, 

 fits this Mouse so closely that I feel bound to identify it as 

 Mus argenteus. 



I can have little doubt that this Mouse is a local development 

 from a sylvaticus-\ike stock, in which the skull has not altered 

 from that of the type, but its peculiar red colour, its size and 

 proportions mark it, as might perhaps have been expected, as 

 the most distinct ally of Mus sylvaticus which I have seen. 



MUS ORTHODON. 



Mus oi't7wdon,~R. Hensel, Zeitschr. deuts. geol. Gesellsch. 1856, 

 p. 279, pi. xiii. figs. 6-10 (aff. Muri sylvatico, fide C. I. Forsyth 

 Major, P.-verb. Soc. Tosc. 1888, p. 129). 



Type (skull) from the Ossiferous Breccia of Mt. San Giovanni, 

 Sardinia. 



In dealing with Mus sylvaticus, I must allude also to Mus 

 orthoclon, which is believed to be very closely allied to it, and 

 the skulls and teeth of which in the British Museum Collection I 

 have examined. The teeth of this species are far more hjpsodont 

 in character, and in immaturity show very deep lateral grooving of 

 the crowns, so that they are also more Vole-like than those of 

 modern Muridae. The first upper molars of the youngest specimen 

 show three internal and three less distinctly marked external 

 convexities. The tubercles have been a good deal worn away, so 

 that their exact disposition can only be guessed ; but the teeth 

 certainly give the impression of having bad all the nine tubercles 

 of Hensel's diagrams present and regularly arranged when quite 



Peoc. Zool. Soc— 1900, No. XXVIII. 28 



