360 



CAENIVOBA 



inflated along inner margin ; outline triangular-flask shaped, the 

 tubular portion of meatus not well defined from rest of bulla ; 

 least distance between bullae about equal to greatest diameter of 

 bulla including meatus. Paroccipital process low and ridge- 

 like, widely removed from inflated portion of bulla. Mandible 

 very robust, the ramus slightly bowed outward posteriorly, its 

 lower margin essentially straight except for a slight upward 

 curve behind level of tooth-row, the depth of ramus at middle 

 about one-third that through coronoid process ; angular process 

 very short ; coronoid process narrowly rounded off above, its height 

 above articular process about equal to width at articular level. 



Teeth. — The teeth are large and strong, with well developed 

 cusps and commissures and relatively small crushing areas, the 

 small premolars of upper and lower mandible fitting closely 

 between each other when jaws are shut; crown area of upper 



molar about equal to that of car- 

 nassial, sometimes less. Upper 

 incisors forming a nearly straight 

 transverse row, the anterior faces 

 of the smaller teeth exactly in line, 

 those of the two larger teeth slightly 

 more posterior ; i 1 and i 2 small, 

 sub-equal, the shafts compressed, 

 the cutting edges rounded, simple ; 

 i 3 higher than the others, somewhat 

 resembling the lower canine in form, 

 its apex curved outward and back- 

 ward beyond level of smaller teeth, 

 its postero-external surface with two 

 concavities separated by a trenchant 

 ridge ; lower incisors subterete, the 

 crown of « 3 obscurely and unsym- 

 metrically bilobed, that of the others 

 simple; cross section of i x about. one-third that of i 3 . Canines 

 robust though not greatly elongated ; shaft simple, without 

 evident cingulum, that of upper tooth slightly curved backward, 

 that of lower tooth abruptly recurved, its axis set obliquely 

 outward. Anterior premolar both above and below well 

 developed and functional, the point of the upper tooth lying 

 internal to that of lower when jaws are closed ; pm 1 small, single 

 rooted, its crown area about equal to that i 2 , its form essentially 

 like that of succeeding tooth, though with cusp relatively less 

 developed ; pm 2 and pm 3 successively larger, two-rooted, the 

 crown area of pm 3 fully three-fourths that of canine, each tooth 

 with a well-developed cusp lying in front of middle of crown, 

 and a distinct anterior and posterior cutting ridge ; cingulum 

 moderately developed ; outline of crown of pm 2 elliptical, that of 

 pm 3 with inner margin bulging inward behind middle, though 

 without developing a definite inner lobe ; pm 2 and pm 3 much like 



FIG. 75. 

 Lutra lutra. Teeth. Nat. size. 



