80 MR. G. E. H. BARRETT-HAMILTON ON [Feb. 7, 



with which everyone is familiar. The upper surface is not of 

 the typical smoky musculus tint, but of a sepia-broun with a 

 grizzled appearance, due to many of the hairs being tipped with 

 rufous. The lower parts of the hairs are exactly of the same shade 

 as in Mils sylvaticus, for a dark specimen of which, at a casual 

 glance from above, the animal miglit almost be mistaken. All 

 these mice — even the very young ones — agree in presenting 

 similar characters, and altogetlier are quite the most distinct local 

 form of Mus musculus which I have ever examined. 



In form and proportions these mice are well-developed large 

 House-Mice, only dilfering in this respect from ordinary mice in 

 being above the average size. The dimensions of the series which 

 I have been able to examine are as follows (in millimetres) : — 



Head Hind 



and body. Tail. foot. Ear. 



^^i1^rS;Io.?S} '' '' '' '' I 



2 (spirit) „ „ 88 81 15 12 I. i898. 



2 „ „ „ 78 79 15 12-5 j 



2 , 87 84 16-5 13 ) 



r Brit. Mus. Coll. nos. 94. 7. 16. 

 2 (spirit), suckling 83 78 18 13 J :> & 3, presented by Mr. 



Q „ „ 85 85 17-5 13 J- Steele Elliott through 



[ Mr. J. E. Harting. 



f Brit. Mus. Coll. no. 96.8.6.1, 



cJ (juv.) (spirit) 75 65 16 10 ] presented by the Kelviu- 



[ grove Museum. 



$ (spirit), very young ... 52 52 14 10 1898. 



f Brit. Mus. Coll. nos. 94. 7. 16. 



— .. .. ••• 65 67 15 ^"^ J 2 & 3 (duplicate), presented 



— „ „ ... 53 60 16 10-5 I by Mr. J. Steele Elliott 



[ through Mr. J. E. Harting 



The arrangement of the mammae is as in 3Ius musculus, there 

 being 10 pairs in all, of which three are pectoral and two inguinal. 



The skulls and dentition of these mice are in general appear- 

 ance and size very musculus-W&e in character, but the triangular 

 narrowing of the internal opening for the nostrils is even more 

 strongly marked than in ordinary specimens of Mus musculus. 

 All the St. Kilda skulls possess this peculiar narrowed palate, a 

 character which I can only find in one out of over fifty specimens 

 of Mus musculus-like Mice in the British Museum collection, and 

 that one is a specimen of the subspecies Mus musculus jalapce 

 Allen and Chapman, from Mexico. The greatest lengths of four 

 skidls from St. Kilda are 22, 22-5, 23, and 23 millimetres. 



It is obvious that, according to the custom of modern naturalists, 

 these two forms of Mice need new names, which I therefore propose 

 to give, leaving the question as to the exact status of the two new 

 forms to be decided when we are in possession of a fuller know- 

 ledge of the other species or subspecies of Mice of the musculus- or 

 sijlvaiicus-Mke groups. As to the desirability of bestowing names 



