800 RODENTIA 



wider posteriorly, its anterior border straight or faintly curved, 

 usually not extending forward quite to level of last molar ; 

 hamulars slightly thickened at tip, curved a little outward, 

 barely or not in contact with bullse ; ectopterygoid well 

 developed, nearly horizontal, its posterior portion spreading 

 considerably beyond outer alveolar line. Mandible slender, with 

 no special peculiarities of form ; coronoid process small but well 

 developed, directed noticeably backward, its extremity about on 

 level with condyle ; angular process long and rather slender, its 

 inner surface with noticeable longitudinal concavity ; dental 

 foramen at level of alveoli ; projection marking root of incisor 

 slight but evident, directly under base of coronoid process. 



Teeth. — Relatively to size of skull the teeth are rather small : 

 alveolar breadth of ro 1 distinctly less than half greatest width of 

 palate between tooth-rows ; alveolar length of upper tooth-row a 

 little less than half diastema. Upper incisor strongly curved, 



Apodemus sylvaticus. 



FIG. 166. 

 Cheek-teeth, (a) slightly worn ; (6) much worn. 



X 10. 



forming nearly half of a circle, its root appearing as an evident 

 protuberance on side of rostrum slightly in front of lower portion 

 of infraorbital foramen ; shaft compressed, nearly triangular in 

 section, its antero-posterior diameter about double its greatest 

 width, the anterior and inner faces flat, joining each other at a 

 well marked nearly right angle, the outer edge of anterior face 

 curving rather broadly into outer face, the curved portion giving 

 this part of the section a somewhat oblique appearance ; posterior 

 face narrow, abruptly rounded, not sharply differentiated from 

 outer and inner faces. Lower incisor slightly longer and much 

 less curved than upper incisor, its root forming a protuberance 

 on outer surface of mandible under base of coronoid process and 

 slightly above alveolar level ; cross-section of shaft essentially 

 as in upper incisor, but anterior surface relatively narrower. 

 Upper molars with tubercles arranged according to a ground- 

 plan of three longitudinal rows of tubercles, those of the median 



