186 BRITISH FOSSIL REPTILES. 



teeth, those of the upper jaw chiefly, of the Mosasaurus Hojfmanni, do not bear out the 

 term " polygonal" which he applies to the crowns of the teeth of that species, as well 

 as to those of his Mosasaurus Maximiliani ; still less can I find these angles so con- 

 stant 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 Iloffmanni that near equality of extent and convexity between the inner and 

 outer surfaces of the crown, which Dr. A. Goldfuss describes (p. 178) and figures in 

 Tab. IX, 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 Iloffmanni ; 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 PI. 2, fig. 1 and Iff, equally difi"er from the typical 

 form of tooth of the Mosasaurus Iloffmanni, and from those of the Mosasaurus Maxi- 

 miliani, PI. 10, fig. 8: the outer surface of the crowns of the mandibular teeth of 

 Mosasaurus gracilis are more convex than those of Mos. Iloffmanni, and are less convex 

 than those of Mos. Maximiliani : 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. Maximiliani. The lower jaw, PL 2, fig. 1, is more 

 slender, less deep in proportion to its length, than in the great Maestricht Mosasaur, and 

 the hinder teeth are relatively smaller and closer together ; I have proposed, 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, b, and c, fig. 1 ; an exact contour of the 

 crown a little above its base is given at PI. 10, fig. 9. The smooth and polished 

 enamel ; the inequality 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 general 

 anchylosis of the fang to the bony walls of the socket, which rise in a pyramidal form 

 from alveolar border of the jaw ; all manifest the peculiar generic characters of the 

 great acrodont marine lizard, Mosasaurus. The maturity of the individual from which 

 the present specimen (PI. 2, fig. 1) has been derived, cannot be inferred from the solidifi- 

 cation and complete development of the anchylosed fangs of the teeth in a class of 

 animals in which those organs are repeatedly shed and renewed : the worn-out teeth, 

 in course of displacement, of the young crocodile, with their alveoli, present in 

 miniature all the senile characters of the corresponding teeth of the mature and aged 

 animal. If, however, the specimen of Mosasaur in question should be adult, it would 

 derive a well-marked specific character from its diminutive size as compared with the 

 Mosasaurus Iloffmanni or Mos. Maximiliani ; being only one third the size of the latter, 



