SQUIRRELS, BEAVERS, DORMICE, AND RATS 245 



1. Mus sylvaticus intermedius is of medium size (the head 

 and body about 4 in. long), but the red of the average coloration 

 is tinged with gray, or even black, owing to many of the hairs 

 of the back being tipped with black in the winter-time. 

 Occasionally this sub-species becomes almost identical in colour 

 with the common mouse. This form is distributed over Great 

 Britain, Ireland, some of the large islands off the west coast of 

 Scotland (but not the Hebrides), and the Channel Islands. 

 Elsewhere it is found in Holland, Belgium, France, and Switzer- 

 land, possibly also in Western Germany and Southern Sweden. 



2. Mus sylvaticus celticus. This is quite a small form of 

 wood mouse, scarcely, if at all, larger than the common mouse. 

 The tail also is not proportionately so very long, while on the 

 other hand the ears and hind legs are longer in proportion. The 

 colour of this form is much darker and grayer. It becomes 

 almost black along the upper surface of the tail and the ridge 

 of the back, while the pure white of the belly is toned to a 

 bluish-gray. This wood mouse has rather a remarkable dis- 

 tribution, being confined in the United Kingdom to Southern 

 and Western Ireland, the Hebrides, and the island of Skye. 

 Elsewhere it exists in Northern Portugal, an interesting instance 

 of what Dr. Scharff styles " Lusitanlan " immigration. 



3. Mus sylvaticus hebridensis. This mouse is rather a large 

 one, but has proportionately smaller ears, bigger hind feet, and a 

 shorter and thicker tail. The colour of the under side is less 

 white (more gray) than in the other sub-species mentioned. 

 The tail is uniformly brownish-gray, and there is no sharp 

 demarcation between the sandy-gray of the upper parts and the 

 dusky-gray of the under side. This large wood mouse is 

 entirely confined in its distribution to the islands of Lewis and 

 Barra, in the Outer Hebrides. 



4. Mus sylvaticus hirtensis. This mouse is still larger than 

 Mus sylvaticus hebridensis, and the under parts are quite buff- 

 colour or yellowish-brown, the upper side being sandy-gray. 

 In other respects, and in the proportions of the ears and feet, 

 it resembles the mouse of the Hebrides. Its distribution is 



