ORYCTOLAGUS 



489 



below ; nasals flattened posteriorly, convex laterally in front, 

 their combined posterior margin deeply emarginate ; nasal branch 

 of premaxillary extending nearly to posterior border of nasal. 

 Outer margin of incisive foramen nearly straight, the outline of 

 the two together narrowly cuneate, the greatest combined l)readth 

 about one-third length. Least longitudinal diameter of palate 

 about two-thirds or three-quarters distance between alveoli of 

 anterior premolars. External pterygoid plate well develo^Ded. 



Teeth. — First upper incisor with root extending somewhat 

 more than half way from aveolus to suture between premaxillai-y 

 and maxillary, its course not distinctly indicated on outer surface 

 of bone ; shaft of tooth about one-third greater in lateral 

 diameter than in antero-posterior diameter, its section nearly a 

 parallelogram in outline, though slightly wider internally than 

 externally ; anterior face of tooth with deep, simple groove lying 

 slightly nearer to internal than to external border ; posterior 

 face with wide, shallow longitudinal concavity, the beveled edge 

 abruptly angled near middle. vSecond incisor elliptical in cross 

 section, flattened antero-posteriorly, the area of its shaft in cross 

 section about one-sixth that of first tooth. Lower incisor witli 

 root extending back nearly or quite to level of front of alveolus 

 of anterior molar, its shaft essentially like that of first upper 

 incisor except that anterior groove and posterior concavity are 

 absent and beveled edge is nearly flat Anterior upper 

 premolar with crown narrowly elliptical in outline, the anterior 

 border with three re-entrant angles, the second of which is 

 deepest, usually extending to about middle of crown. Anterior 

 lower premolar irregularly squarish in outline, narrower anteriorly 

 than posteriorly, with two deep, rather wide grooves on outer side, 

 a narrow re-entrant angle at middle of anterior border and a 

 slight projection at middle of inner border ; anterior section of 

 tooth decidedly larger than posterior section, its posterior enamel 

 border forming a conspicuous, irregularly folded transverse ridge 

 slightly behind middle of crown. Posterior upper molar 

 essentially like second incisor. Posterior lower molar consisting 

 of a larger elliptical, transversely flattened anterior section, and 

 a smaller posterior subterete section, the enamel of each section 

 forming a complete tube, the area of crown about one-third that 

 of second molar. Second, third, fourth and fifth upper molariform 

 teeth essentially alike, though slightly decreasing in size from 

 before backward, the crown narrowly elliptical, the inner 

 and outer margins notched or flattened (varying according to 

 wear), the re-entrant enamel fold extending from inner border 

 nearly across crown and dividing it into essentially eijual halves, 

 its anterior border crenulate. Second, third and fourth lower 

 molariform teeth essentially alike in size and form, the crowns 

 much longer than in the corresponding upper teeth, each con- 

 sisting of two narrowly elliptical sections with very narrow, 

 almost pointed extremities, the anterior section decidedly larger 



