394 PROCEEDINGS OF THE GEOLOaiCAL SOCIETY. [Jime 23, 



tenor of the jaw-bone, owing to the increasing dimensions of the 

 tooth-roots towards the bottom of the alveoli. 



^Dimensions of Lower Jaw. 

 Eight ramus. inches. 

 Length from posterior extremity to the hindermost visi- 

 ble tooth 30 



Length of articular surface measured from its ant. int. 



angle to the postarticular ridge 2*7 



Length of postarticular surface *. 2*7 



Distance of coronoid process from the postarticular 



ridge 7-5 



Horizontal distance between coronoid process and angle 4 



Distance of angle from posterior extremity of jaw .... 5 



Depth of jaw at angle 4'5 



„ at coronoid eminence 6 



„ at articular surface 3-5 



Teeth. — Of these several are in situ, some have fallen out of their 

 sockets and lie scattered in the matrix, and others are loose. They 

 vary much in size and in length, but they may very properly be 

 called slender and tapering. They are slightly incurved, and curved 

 slightly backwards. In the fully grown teeth, a long root or fang 

 buried in the alveolus, a long, tapering, enamelled crown, and a rela- 

 tively long intermediate neck without enamel are distinguishable. 



The fang is subcylindrical. Some have a slight lateral compres- 

 sion, giving to their cross section an egg-shape — the smaller end 

 turned backwards. They have a remarkably large, conical pulp- 

 cavity, open below, and ascending through the neck a long distance 

 into the crown. Their outer surface is finely striated longitudi- 

 nally, and it is distinguished by its light brown colour and by its 

 want of polish from the highly polished deep madder-brown crown. 

 This latter is laterally compressed, unequally convex, the outer 

 surface being less swollen than the inner ; it is also two-edged, and 

 the edges, which are back and front, are finely notched. In a 

 strong light, the serrature is recognizable by the unaided eye, and 

 it is always distinctly perceptible to the touch. 



The posterior edge begins rather earlier than the anterior on the 

 neck of the tooth ; and the first two or three lines are unbroken, A 

 shallow marginal depression of the outer surface runs parallel to the 

 notched edges. The highly polished crown is overlaid with very fine, 

 closely-set, longitudinal striae just visible to the unaided eye in a 

 good Hght, the striae scarcely rising above the surface. On the more 

 convex inner surface a few broader, widely set, parallel striae are 

 prolonged from the lower limit of the enamel for some distance 

 upon the crown, but they do not reach its top. Some of the crowns 

 are marked with faint annular indentations. 



Succession of the Teeth. — The presence of the germ of an imma- 

 ture crown in the pulp-cavity of a fully-grown tooth, the occurrence 



