274 PTERODACTYLUS. 



regular interspaces, slightly increasing as the teeth are placed further 

 back. In the specimen described by Soemmering there are on the 

 preserved side of the head nineteen teeth in the lower jaw ; and eleven 

 in the upper jaw, which is probably only a portion of this series, but 

 at least gives sixty teeth in all. There is an orifice in the jaw at the 

 inner side of the base of each tooth, whence Cuvier supposes the 

 teeth of replacement to issue. (1) 



In the Pterodactylus crassirostris (PL 63 a, fig. 6) the teeth are 

 relatively fewer, more unequal, but for the most part much larger than 

 in the previous species, and the jaws are correspondingly shorter and 

 stronger. The teeth are long, slender, very acute, sub-compressed and 

 slightly curved ; they have been described as arranged or approximated 

 in pairs, but this is the case with a few only, and the hinder tooth is 

 always the smallest ; whence I conclude that it was a successional tooth, 

 which has been developed in the same relative position to its predecessor 

 as in the great Varanus, (compare figs. 6 & 9, PI. 63 a). The inter- 

 maxillary bone, in the specimen figured, contains four teeth on one 

 side, of which the first three are of small size ; there are seven teeth 

 in the maxillary bone of the same side, of which the hinder ones, 

 that extend beneath the orbit, are the shortest ; the corresponding 

 ramus of the lower jaw contains six teeth ; the supposed successional 

 teeth are included in the preceding enumeration. 



In the Pterodactylus medius the base of the teeth have been 

 stated to be hollow, as in the teeth of the crocodile, and to contain 

 the germs of their successors ;(2) the right half of the lower jaw 

 contains sixteen teeth, of nearly equal size, the hinder ones becoming 

 smaller. They are simple, conical, slightly recurved, compressed and 

 smooth. 



In the Pterodactylus Munsteri the teeth are slender, recurved, 



(1) " On en voit de tout semblables dans le sauvegarde, et surtout dans la dragone {Thorictes 

 draccenn)." I have not observed in any existing reptile this mode of emergence of the successional 

 teeth, as in Mammalia, by an outlet distinct from the socket of the previous tooth. In the 

 great safe-guard (Varanus), the successional teeth rise from the alveolar groove behind those 

 which they succeed, as shown in PL 63 a, fig. 9. In the Pterodactylus medius the germs of the 

 young teeth have been observed in the basal cavities of the old, as in the crocodile. — See Mun- 

 ster, Nova Acta, Nat. Cur. t. xv, 63. 

 (2) Munster, loc. «it. 



