600 RODENTIA 



greater than depth at same region, extreme anterior portion 

 much narrower ; nasals gradually narrowing from before back- 

 ward, their posterior extremity bluntly pointed, slightly exceeded 

 by nasal ioranches of premaxillaries. Incisive foramina long and 

 narrow, parallel-sided, the width of the two together a little 

 more than one-half length ; anteriorly they extend to within 

 about 4 mm. of alveoli of incisors, ^josteriorly to within about 

 3 ram. of aveoli of molars. Bony palate with no special features ; 

 a faintly indicated median ridge continuous with septum between 

 incisive foramina ; mesopterygoid fossa about three times as long 

 as wide, its broadly rounded anterior extremity scarcely extending 

 to level of alveolus of vP, the plate-like, ill-defined hamulars in 

 contact with auditory bullfe ; ectopterygoids well developed, 

 lying, except at their anterior extremity, at a higher (more 

 clorsal) level than the pterygoids. Mandible slender, the ramus 

 strongly curved ; coronoid process rising decidedly above condyle, 

 conspicuously curved backward ; angular process long, curved 

 upward and outward, its upper margin with a well developed 

 thickening or supplemental outer plate. 



Teeth. — Upper incisor with root extending to infraorbital 

 foramen, at front of which it produces a noticable swelling, the 



Fig. 119. 

 Cricetus cricetus. Teeth X 0. a, tinworn ; h, slightly worn. 



shaft slightly and somewhat obliquely compressed, the antero- 

 posterior diameter a little exceeding transverse diameter, the 

 anterior face broadly rounded, decidedly wider than posterior 

 face, that of the two teeth essentially in line with each other ; 

 cutting edge sloping upward toward the middle, the two edges 

 together forming a broad but evident angle ; lower incisor with 

 root extending nearly to base of coronoid process and forming an 

 evident tubercle on outer side of mandible slightly above level of 

 grinding surface of molars ; shaft oval in cross section, the inner 

 side somewhat flattened, the antero-posterior diameter about 

 double transverse diameter, the anterior and posterior faces 



