PLECOTUS 259 



alveolus of ijiner incisor ; anteorbital foramen small, close to rim 

 of orbit, its oritice over parastyle of first molar ; lachrymal fora- 

 men slightly above and behind it, on inner edge of orbit. Palate 

 rather broad and short, sti'ongly concave both laterally and 

 longitudinally, the anterior emargination small, scarcely extend- 

 ing back to level of middle of canine ; posterior extension of 

 palate squarish, slightly longer than wide, with slightly developed 

 median spine ; mesopterygoid space somewhat wider than deep. 

 Zygoma slightly but evidently expanded at middle. Mandible 

 slender, but noticeably deeper at symphysis than behind tooth- 

 row ; coronoid process moderately high, the upper margin of 

 posterior section of mandible oblique-concave ; angular process 

 rather heavy, scarcely or not expanded at tip. 



Teeth. — The teeth are rather small relatively to size of skull. 

 Inner upper incisor about half as high as canine, with large 

 secondary cusp slightly above middle of shaft, the outline of 

 crown oval, its long axis in line of tooth-row ; outer upper incisor 

 about half as high as inner, its apex a little below secondary cusp 

 of larger tooth, its secondary cusp well developed, on inner side, the 

 outline of crown ovate, with long axis perpendicular to tooth-row 

 and narrower extremity directed inwards. Lower incisors closely 

 crowded but slightly imbricated, the row broadly (J -shaped ; the 

 crown area increases regularly from first to third, by addition to 

 postero-internal portion ; cutting edge obscurely trifid ; i^ with 

 well developed postero-internal tubercle. Upper canine small, 

 scarcely higher than main cusps of molars, its shaft nearly terete, 

 with slightly developed posterior cutting edge, on each side of 

 which lies an evident groove ; cingulum complete, without cusps. 

 Lower canine small, slightly exceeding molars in height, its 

 shaft concave posteriorly, flattened interiorly, evenly convex 

 antero-externally ; cingulum well developed, forming a prominent 

 antero-internal secondary cusp. Anterior upper premolar 

 perfectly in tooth-row, about as large as outer incisor, though 

 more robust, its crown sub-terete, about one-third that of canine 

 in basal area, its shaft with evident posterior cutting edge ; large 

 premolar with crown area about two-thirds that of first molar, 

 the inner side very narrow and without crushing surface, the 

 antero-internal cusp slender but well developed. Crown area of 

 anterior lower premolar about half that of canine, that of 

 posterior premolar nearly equal to that of canine, that of middle 

 premolar a little more than half that of first ; first sub-terete, 

 second oval with long diameter of crown lying aci'oss tooth-row, 

 third squarish with antero-external corner rounded off; cusp of 

 first about half as high as canine, that of second a little shorter, 

 that of third a little longer ; cingulum well developed but not 

 forming true secondary cusps. Upper molars narrow internally, 

 the protocone with rather short base, the hypocone absent or 

 barely indicated ; metacone decidedly higher than paracone ; 

 styles and commissures well developed, though mesostyle of m'^ 



s 2 



