THE ISLAY SHREW 



727 



SKULL MEASUREMENTS IN MILLIMETRES :- 



The skull agrees in form and size with that of 5. a. castaneus, but 

 attains rather larger dimensions than skulls of the latter species 

 from northern Britain and the Inner Hebrides. 



The teeth agree in form with those of S. araneus, but there is 

 no trace of pigment upon the hypocones of the upper cheek-teeth, 

 nor on the protocone of ;«3. The posterior unicuspid tooth /£ tends 

 to disappear, as shown by the following statistics : — 



p2 present on both sides of the jaw, 7 individuals, or 437 per cent. 

 „ absent from one side „ 4 „ 25 „ 



„ „ both sides „ 5 „ 31-3 u 



When p2 is absent the four remaining unicuspid teeth appear to be 

 somewhat enlarged. 



Status : — By colour and dentition S. grantii is clearly differentiated 

 from all European members of the genus So7-ex. Some of these, such 

 as S. araneus araneus and a. tetragonurus, have the back as dark, but 

 none shows the conspicuously contrasted sides. 5. grantii may 

 perhaps be regarded as an insular development from 5. a. castaneus. 

 It has maintained or acquired slightly larger dimensions than has 

 the latter in the more northern parts of its range. The Islay Shrew 

 has developed a peculiar colour pattern, and is now well on its way 

 to reduce the number of the unicuspid teeth, perhaps because of a 

 tendency to enlarge the anterior members of the series. The Shrew 

 inhabiting Jura, while definitely a form of 6'. araneus, is geographically 

 and morphologically the connecting link between 5. a. castaneus and 

 S. grantii; it has the small size and the dental characters of northern 



