CRETACEOUS REPTILES. 381 
Mazimiliani, accurately describes and figures the finely dentated character of the 
two opposite longitudinal ridges of the crown; but the feeble indications of 
angles observable in some of the teeth, those of the upper jaw chiefly, of the 
Mosasaurus Hofmanni, do not bear out the term ‘ polygo- Fig. 2. 
nal’ which he applies to the crowns of the teeth of that 
species, as well as to those of his Mosasaurus Maximilian, 
(fig. 2) ; still less can I find these angles so constant and 
regular as to divide the outer surface of the crown into 
five, and the inner surface into seven facets: nor have I 
seen in any maxillary or mandibular tooth of Mosasaurus 
United States. 
Hofmanni that near equality of extent and convexity be- Ree eee 
tween the inner and outer surfaces of the crown, which  Mosasaurus Maximiliani. 
Dr. A. Goldfuss describes (p. 178) and figures in tab. 9. fig. 4 of the memoir 
above-cited. If that figure accurately represents a maxillary tooth of the same 
species of Mosasaurus as the one described by Cuvier and recorded by V. Meyer 
and Pictet under the name of M. Camperi and Hofmanni ; and if the outer surface 
of the crown is ever flat or level, the range of variety between the two extremes 
of flatness and convexity is greater than I have yet found in any of the equally 
well-marked forms of teeth in other fossil reptiles. 
The teeth in the specimens of upper and lower jaw of the species of Mosasaur 
from the chalk-pit at Offham, Sussex, now in the Museum of Henry Catt, Esq. 
of Brighton, and figured of the natural size in Pl. XX XVII. fig. | & 1 a, equally 
differ from the typical form of tooth of the Mosasaurus Hofmanni and from those 
of the Mosasaurus Mavimiliani : the outer surface of the crowns of the mandibular 
teeth of Mosasaurus gracilis are more convex than those of Mos. Hofmanni, and 
are less convex than in Mos. Mavimiliani: not any of the teeth of Mosasaurus 
gracilis present that angular disposition of the enamel which gives the polygonal 
form to the pyramidal crowns of the teeth of the Mos. Mawimiliani (fig. 2). The 
lower jaw is more slender, less deep in proportion to its length, than in the 
great Maéstricht Mosasaur, and the hinder teeth are relatively smaller and 
closer together ; I propose, therefore, to indicate the species by the name of 
Mosasaurus gracilis. The general form of the crown of the teeth in Mos. gracilis 
is shown at a and 3, fig. 1. Pl. XXXVIL.; an exact contour of the crown a little 
above its base is given at c, fig. 1. The smooth and polished enamel ; the in- 
equality of the outer and inner sides of the crown, such as it is; the implanted 
fang of the tooth thickly coated by a coarse osseous cement ; the anchylosis of 
3D 
