Vol. 55.] TEOM KHJETIC EEDS NEAK BRIDGEI>JD. 91 



now is. There is no ornamentation other than a slight streaking of 

 the surface. A small part of the. bone is wanting in front, as may 

 be seen if this portion (PI. X, fig. 2) be compared with the corre- 

 sponding part of fig. 1. Anteriorly a row of five foramina may 

 be seen below the alveolar border, and these are followed by a 

 shallow groove, which, descending a little, is continued to the 

 hinder end of the cast, almost parallel with the alveolar border, 

 and at about | inch from it ; along this groove there are elongated 

 depressions at irregular intervals, but these are not foramina, 

 as might be supposed. Near the lower margin also there is a row 

 of six or seven smaller foramina, and after an interval a groove 

 continues the line to the end of the specimen. 



The lessening of the depth of the jaw between the third and 

 fourth of the larger teeth (PI. X, fig. 2) is due to the way in 

 which the jaw was divided in the splitting open of the stone ; 

 nothing of this is seen on the inner half (PI. X, fig. 1). 



The teeth were lodged in deep sockets ; six of them, fully de- 

 veloped, are still in place (PI. X, fig. 1). The anterior tooth is the 

 largest, being 29 mm. above the outer margin, 12 mm. from before 

 backward, and about 6 mm. thick. The hindermost of these six 

 teeth stands only 14 mm. above the jaw. Pive other teeth may 

 be seen projecting, more or less, from their alveoli ; and on the 

 inner side, at the bases of the fourth and of the hindermost large 

 teeth, the points of two successional teeth may be seen in the pits 

 which have already been mentioned (PI. X, figs. 1 a-h & 4). Six 

 of the alveoli are empty. 



The teeth are strongly curved ; their posterior concave margins 

 are serrated to within a short distance of the jaw, while the 

 anterior convex margins are only serrated for about two-thirds of 

 their length. The second of the large teeth shows the serration most 

 perfectly (PI. X, fig. 3) : its concave margin stands 23 mm. above 

 the jaw, and 20 mm. of this are sharp and serrated ; the front 

 convex margin measures 25 mm., of which the upper 16 mm. are 

 sharp and serrated, while the lower part is rounded and not serrated. 

 This proportion of serration on the anterior margin is practically 

 the same on all the teeth. 



Prom the foregoing remarks the mode of succession' of the 

 teeth may be clearly understood. The new teeth are developed in 

 or close to the little pits seen on the inner sides of the functional 

 teeth, where their points first appi»ar, as shown at the bases of 

 the fourth and sixth large teeth (PI. X, fig. l,a & h). Doubtless, 

 as in some well-known reptiles, the pressure of the new and 

 growing tooth upon the inner side of the old one caused its 

 absorption, until at length the young tooth would occupy the 

 inside of the fang of the old tooth. This stage is not shown in 

 the present specimen. The continued growth of the new tooth 

 causes the absorption of the old one, until it is so weakened that 

 it is broken off or falls out. and then the new tooth is found occu- 

 pying the middle of the alveolus. Several such young teeth may 

 be seen protruding more or less from their alveoli in this specimen. 



