APODEMUS 



799 



somewhat quadrate in section, the annulations distinct, about 

 eighteen to the centimeter at middle ; hairs rather sparse, not 

 concealing the annulations at middle but forming a small though 

 evident pencil at tip, their length equal to width of 2J rings. 

 Mammae: p 1-1, i 2-2 = 6. 



Colour. — For detailed description of colour see accounts of 

 subspecies. 



Skull. — The skull is moderately large, smoothly rounded, and 

 without any striking characteristics. Dorsal surface straight 

 and gradually rising from tip of nasals to middle of frontals, 

 then moderately convex to back of interparietal, the convexity 

 most strongly marked over middle of parietals ; ventral profile 

 horizontal to back of molars, then bent rather abruptly 

 downward to lowest portion of bulla. 

 Brain-case ranging from broadly ovate 

 to sub-circular in outline when viewed 

 from above, its surface everywhere 

 smoothly rounded except for the faintly 

 angular posterior border to orbits, a 

 slight perpendicular ridge in mastoid 

 region, and in very old individuals a 

 barely indicated lambdoid angularity. 

 Interparietal rather large but narrow, 

 its extremities gradually tapering and 

 usually rather sharp-pointed. Posterior 

 aspect of occiput low and narrow, much 

 exceeded in height by the median region 

 of brain-case ; paroccipital processes small 

 and inconspicuous, close to outer surface 

 of condyle. Floor of brain-case with no 

 conspicuous features, the basioccipital 



with low median ridge and shallow lateral excavations ; bulla 

 moderate, smoothly rounded, the large meatus with faintly 

 indicated tubular rim. Interorbital region somewhat abruptly 

 though not very narrowly constricted, flat above, the margins 

 rounded anteriorly, squarely angled posteriorly but never raised, 

 and bead-like. Zygoma slender, rather abruptly but not widely 

 spreading anteriorly, the median portion of the two arches 

 essentially parallel when viewed from above. Plate forming 

 outer border of infraorbital canal well developed, its anterior 

 border perpendicular. Rostrum slender, not elongated, the 

 nasals simple, narrowing gradually backward, their posterior 

 termination squarely truncate or bluntly pointed, usually a little 

 in front of posterior extremity of nasal branches of premaxillaries 

 and of level of front of lachrymal. Incisive foramina rather 

 long, parallel-sided, extending from about 1-1 • 5 mm. behind 

 incisors to level of anterior root of m 1 ; palate nearly flat, without 

 special features, the portion formed by palatine bones extending 

 forward to middle of m 1 ; mesopterygoid space narrow anteriorly, 



FIS. 165. 

 Apodemus aylvaticus. Nat. size. 



