VEETEBEATES. 108 



usually show marked tendency to elongation in the direction of the 

 inrollment of the tooth ; the inner surface shows a dense layer of 

 enamel with fine lines of growth parallel with the inner margin. 

 Greatest transverse diameter of the tooth, 20 mm. ; length along 

 antero-lateral border, 6.5 m m. ; greatest longitudinal diameter, 10.5 

 mm. 



Posterior tooth of the mandible sub-quadrangular in outline, rather 

 strongly inrolled and longitudinally arched ; corresponding in size with 

 the previously-noticed form. The moderate and regular arching of 

 the inner margin interrupted by the broadly-rounded base of the 

 coronal prominence; antero-lateral border with a slight oblique 

 course outward and backward, enamel fold relatively deep and in- 

 beveled to the shallow, channeled basal rim ; postero-lateral border 

 very gradually converging, making an angle of 10 or 15 with the 

 opposite side, the narrow enamel fold well denned from the basal 

 portion, which forms a shallow rim projecting considerably beyond 

 the limits of the crown. Median prominence regularly and broadly 

 arched transversely, culminating a little posterior of the median 

 line, and occupying quite half of the lateral diameter of the crown; 

 posteriorly, the slope merges into the shallow concavity bordered 

 exteriorly by the gently-upraised alation, in front defined by a faint 

 angulation from the wide, slightly convex belt intervening between 

 the median lobe and the antero-lateral border. The surface of the 

 anterior belt is marked by faint, revolving plicae, and along the 

 inner margin the enamel coating shows more or less distinct parallel 

 undulations, or lines of growth, the outer half of the coronal surface 

 exhibiting the usual evidences of excessive trituration, the entire 

 coronal area minutely and closely punctate, the punctse showing the 

 longitudinal elongation precisely after the manner observed in con- 

 nection with the opposed maxillary teeth. Breadth across inner 

 margin, 17 mm. ; longitudinal diameter along the axis of median 

 lobe, 9.5 mm ; length along antero-lateral border, 7 mm. 



The two forms of teeth described above are represented in equal 

 numbers in the collections, and their uniform association and agree- 

 ment in size and superficial characters preclude any doubt as to 

 their specific identity. As commonly occurs in the teeth of this 

 family, in consequence of the attenuation of the borders, seldom is 

 a specimen met with showing the antero-lateral border entire, and 

 indeed in the majority of examples of the mandibular form the 

 posterior wing or alation is also mutilated or broken away. 



