YEETEBRATES. 361 



belt, as in G. inerassatus, extends well up the convex face in a wide belt 

 interrupted by obscure imbrications ; it is, however, in comparatively 

 few individuals that the coronal folds are well preserved, and probably 

 in no instance were they as strongly developed as in the above men- 

 tioned form. In the teeth which represent the normal aspect of the 

 present form, the root is apparently produced downward in a plane 

 nearly vertical to that of the crown, moderately thick, nearly median, 

 deeply channeled beneath the produced border of the concave face, less 

 so in the opposite side, and slightly beveled along the lower margin, 

 inferior surface well-defined, very oblique, or nearly corresponding to the 

 plane of the convex crown face, in depth equal to or exceeding the 

 greatest elevation of the crown. 2. Among these teeth there are some 

 which present a strong, irregular serration of the crest, as shown in fig. 

 7, PI. X ; the root is vertical as in the before mentioned variety, while 

 in other respects they are very similar, the denticulate character grad- 

 ually merging into those in which the crest is quite worn. 3 A third 

 variety presents a more regular crest line, which, although it is not 

 central, shows the side corresponding to the convex face to be slightly 

 excavated, the root more obliquely produced in the plane of the convex 

 crown-face, aud constituting a connecting link between the above men- 

 tioned and the following extreme varieties. 4. Under this head is 

 included a series of teeth which might at first seem to be quite dissimi- 

 lar from their associates, as above described. They are distinguished 

 by their uniform outline, the two longer sides being nearly parallel, the 

 coronal crest nearly central and moderately arched, the concave face 

 gently depressed, the opposite face but slightly arched vertically, some- 

 times quite plane or faintly depressed ; the basal folds are obsolete in 

 all the examples before us. The root, which in the previously men- 

 tioned varieties is more or less nearly vertical, in the present examples 

 is remarkable for its extravagant obliquity, indeed so much so that in 

 some extreme cases it forms an uninterrupted plane with the convex 

 crown face, or even uniting at the basal limit at a slight angle, in some 

 the basal border being slightly raised, in others, again, simply defined 

 by the angulation and the perceptible difference in the superficial struc- 

 ture of the crowu as compared with that of the basal portion, as shown 

 iu fig. 10. However, the gradatiou which these latter teeth exhibit, in 

 connection with the gradation observed in the preceding varieties, seems 

 to afford conclusive evidence of their specific identity. The surface 

 ornamentation is much the same in all the varieties, consisting of a 

 more or less distinct, minute striato-punctation when not concealed by 

 the dense, smooth, enamel-like coating. 



From a careful examination of the above noticed teeth, it would 

 appear that they probably constituted the variable dentition of one and 



