VERTEBRATES. 133 



versed by a slight angulation, whence the surface rises with slight 

 concavity into the moderately upraised alation, along the border of 

 which the -thickened enamel is rounded over in a relatively wide in- 

 beveled fold to the basal portion. The inner edge of the crown, in 

 some specimens, shows a widish belt of the dense enamel without 

 blemish, as it was when enveloped in the formative membrane ; 

 where the surface is exfoliated and abraded the coarse punctate 

 structure is revealed. The surface is ordinarily marked by fine 

 closely arranged punctae, sometimes showing a disposition toward 

 transverse arrangement, but otherwise smooth and destitute of cor- 

 rugations. Greatest transverse diameter of a mature tooth across 

 inner margin 16 mm. ; length along crest of the anterior lobe to the 

 outer inrolled margin 7 mm. ; or about as great again as the length 

 of the extreme antero-lateral border. 



Maxillary posterior teeth eubelliptical in outline, strongly inrolled 

 along the outer margin. Antero-lateral border with a slightly 

 oblique forward course, basal portion channeled and denned above 

 by a relatively strong, inbeveled coronal fold ; postero-lateral border 

 converging toward point of inrollment at an angle of 30 to 40 

 with the opposite side, making a gentle regular curve from the 

 produced, acutely-rounded posterior extremity to the inrolled outer 

 margin, basal portion rather deeply channeled and expanded beyond 

 the coronal border; inner margin broadly arched round the base of 

 the posterior prominence, with a broad concavity in the region of 

 the median depression, somewhat angularly arched round the ante- 

 rior lobe to the obtuse anterior angle. Contour of the coronal 

 regions strongly marked, posterior lobe occupying nearly half the 

 lateral diameter of the crown, presenting a broad gentle slope pos- 

 teriorly, slightly convex above and faintly depressed on nearing the 

 border, which is denned by a rather strong inbeveled enamel fold; 

 the anterior declivity abruptly descends from the more or lees 

 angularly rounded crest with slight concavity, merging into the 

 deep, wide median depression; anterior lobe culminating in a 

 sharply rounded crest flanked by nearly equally steep slopes on 

 either side, that in front terminating in a narrow revolving groove 

 or angulation which is bordered by the narrow, rounded marginal 

 fold of the anterior border. Surface appearances the same as noted 

 in the mandibular teeth above described, with the same tendency 

 to transverse disposition of the punctse in lines more or less coinci- 

 dent with the outline of the inner margin of the tooth. A medium 

 size individual measures in greatest transverse diameter between 



