1899.] ON THE MICE OF ST. KILDA. 77 



Since then I have met with two instances of the same kind in the 

 skulls of Marsupials. The first of these I detected in the skull of 

 an apparently adult Macropus r/iganteus in the Museum of the 

 Eoyal University of Ireland. In this case the bone was only 

 recognizable on the right side as a distinct ossification, while on 

 the left the suture between it and the lachrymal had disappeared. 

 The second instance I found in the skull of an adult Wombat 

 {Phascolomys pUtyrliinus) in the Natural History Museum of 

 Queen's College, Belfast. Here the bone was well-developed on 

 both sides of the skull, and distinctly separated by suture from 

 the frontal, nasal, maxilla, and lachrymal. It is worthy o£ note 

 that, in his memoir on the 'Modifications of the Skeleton in the 

 Species of Phascolomi/s,' the late Sir Eichard Owen does not seem 

 to have recognized this pair of bones, notwithstanding that they 

 are cleai-ly displayed in more than one beautiful figure of the skull 

 by his artist, Mr. Smit. 



The occurrence of such bones in Mammals so far removed from 

 one another as a Lemur, a Hippopotamus, and two Marsupials 

 suggests the probabihty of then* being less uncommon in the 

 mammalian skull than would at first appear, and I have little 

 doubt that any naturalist who possesses the requisite time and 

 opportunities for conducting the research in a large osteological 

 museum would add to the list of such instances. 



3. On the Species of the Genus 3Ius inhabiting St. Kilda. 

 By G. E. H. Barrett-Hamilton, F.Z.S. 



[Received December 5, 1S9S.] 

 (Plate IX.) 



The existence of any wild species of Mouse on the isolated rock 

 of St. Kilda is an occurrence so apparently unlikely, that when 

 in 1895 a specimen of a 2Ius sylvaticus-]ike species was found 

 amongst some examples of Ihis viusculas sent thence to the British 

 Museum in spirit, it was received wdth an amount of surprise 

 certainly equal to the importance of the discovery. The specimen, 

 a young male, had been obtained and was presented to the Museum 

 by Mr. J. Steele Elliott \ It was a very remarkable one, and bore 

 unmistakable evidence of having come from an out of the way part 

 of the world. Its chai-acteristics were a larger foot and a smaller 

 ear than the corresponding organs of typical J/i<s sylvaficus, while, 

 what was no less noticeable, the very characteristic snow-white 

 colour of the belly of our common Eield-Mouse was in this indi- 

 vidual replaced by a uniform rufous hue shading imperceptibly 



^ Mr. Steele Elliott appears to have been the first person to collect specimens 

 of the Mice of St. Kilda. The occurrence there of mice of some sort was, however, 

 k))own fireviously to the outer w.jrld, and Seton states that " A cat is to be seen 

 in almost every cottage, the mouse being the only wild animal on the island, 

 and rats are still unknown " (' St. Kilda, Past and Present,' 1878, p. 132). 



