860 



RODENTIA 



Rostrum deepened anteriorly so that dorsal profile is nearly 

 horizontal throughout. Upper border of plate forming outer 

 wall of infraorbital foramen nearly horizontal and very abruptly 

 rounded off anteriorly, the plate wider in proportion to its height 

 than in Epimys rattus. In other respects the skull closely 

 resembles that of E. rattus apart from its larger general size. 

 The auditory bullae tend, however, to be less inflated and the 

 incisive foramina to be slightly shorter and wider, their posterior 

 border usually not extending quite to level of anterior molar 

 root. 



Teeth. — Incisors as in E. rattus. Molars with number of 

 roots and general size and proportions of crowns as in E. rattus, 

 but upper teeth showing a greater tendency toward reduction 

 of the outer cusps. First upper molar with distinct cingulum- 



like ridge at anterior base of crown, 

 this ridge in some specimens showing 

 a tendency to develop one . or more 

 minute tubercles ; first lamina notice- 

 ably distorted by the nearly complete 

 suppression of t'3, which is so reduced 

 as to be practically nothing more than 

 an outward prolongation of the outer 

 border of V2, usually without trace 

 of antero-external re-entrant angle ; 

 second and third laminae essentially 

 as in Epimys rattus. Second upper 

 molar like that of E. rattus except 

 that <9 is greatly reduced in size and 

 completely merged in outer base of 

 t8, the third lamina thus forming a simple biconvex terminal 

 heel. Third upper molar essentially as in Epimys rattus, tl 

 equally well developed, but other elements of tooth less distinct. 

 Lower molars differing from those of Epimys rattus in the less 

 evident tendency to develop supplemental tubercles at outer 

 extremities of spaces between the laminae, such rudiments of the 

 small tubercles as may be present usually appearing as slight 

 thickenings at outer extremities of the laminae. 



Measurements. — Adult male from Cortachy, Forfar, Scotland : 

 head and body, 226 ; tail, 179 ; hind foot, 415 ; ear, 20. Adult 

 male from Cambridge, England : head and body, 242 ; tail, 185 ; 

 hind foot, 42. Adult male from Tiverton, Devonshire, England : 

 head and body, 238; tail, 212; hind foot, 42; ear, 21. Adult 

 male from Roydon, Norfolk, England : head and body, 250 ; 

 tail, 218 ; hind foot, 45. Adult male from Hampton, near 

 London, England : head and body, 255 ; tail, 187 ; hind foot, 41 ; 

 ear, 20-5. Adult male from Kilmanock, Waterford, Ireland : 

 head and body, 242 ; tail, 209 ; hind foot, 44 ; ear, 20. Adult 

 male and female from Upsala, Sweden : head and body, 250 and 

 252 ; tail, 183 and 183; hind foot, 41 and 41. Adult male and 



Fig. 17". 



utys iion'i'gicus. 

 X5. 



Cheek-teeth. 



