404 ME. G. E. H. BARRETT-HAMILTON ON [Apr. 3, 



This gentleman, to whose kindness I am indebted for permission 

 to examine the whole of his interesting series of 14 specimens 

 of this subspecies, has drawn my attention to the curious fact that 

 the young males appear to lose the dull hues of immaturity of 

 the upperside, and to don the reddish colour of maturity, at an 

 earlier age than do the females, so that young males and females 

 of the same age are actually distinguishable by their colour alone. 

 If this be so, it would seem to be a quite unique case in the 

 Rodentia, an order among the species of which, as I am informed 

 by my friend Mr. Oldfield Thomas, sexual differences are exces- 

 sively rare. 



4. MlJS SYLTATICUS HIRTEXSIS. 



Mus hirtensis, Barrett-Hamilton, Proc. Zool. Soc. 1899, p. 81. 



Type. No. 94.7.16.1 (British Museum collection), a young male 

 collected by Mr. J. Steele Elliott at St. Kilda. 



Distinguishing Characteristics. Closely allied to M. s. hebridensis, 

 from which, however, it differs in its slightly larger size, and also 

 in the greater amount of buff or yellowish-brown coloration on the 

 underside. Like Mus s. hebridensis, it differs from M. s. inter- 

 medins, apart from its greater size, in the more uniform coloration 

 of the upper surface of the body, in the absence of the clearly 

 defined white underside, and in the longer feet and shorter ears. 



The skull is similar to that of M. s. hebruleasis, but appears to 

 be slightly larger, reaching a length of 29 mm., and equalling in 

 size that of the largest specimen of M. s. wintoni. 



Distribution. Known only from the island of St. Kilda. 



General Remarks. This is another interesting insular deve- 

 lopment of Mus sylvaticus, the status of which has been already 

 discussed (op. cii.). Like M. s. hebridensis, it seems to have been 

 first obtained by Mr. J. Steele Elliott, who presented the type 

 specimen 1 to the British Museum in 1894. This was supple- 

 mented by a series procured for me by my friend Mr. Henry Evans, 

 of Jura, Scotland, in 189b. I have already suggested the possi- 

 bility that this Mouse may be indigenous to St. Kilda, a suggestion 

 which is heightened by the fact that, as Mr. Steele Elliott informs 

 me, "there is no landing-place at St. Kilda, so rats and mice stand 

 a poor chance of getting on the islands from any boats that call, 

 especially as provisions taken on are also very limited " 2 . 



5. Mus sylyaticts typicts, Linnaeus, Syst. Nat. ed. 10, 1758, 

 p. 02. 



Mus Jlavicollis, H. B. Melchior, Den danske Stats og Xorges 



1 Trapped in a hole in a loose stone wall at a height of about 6 feet from the 

 ground. 



2 Mr. R. M. Barrington writes me that when he was at .St. Kilda in 1881 he 

 found a dead and dried specimen on the headland opposite the Doon, but, 

 unfortunately, did not preserve it. 



