260 MOSASAURUS. 



meters : their secondary curvatures and branches resemble those in the 

 tooth of the Varanus : the commencement of the subdivision of the mass 

 of dentine, by the divergence of the calcigerous tubes from secondary 

 centres, after quitting the main pulp-cavity, is shown in the reduced 

 figure of a magnified view of the half of a transverse section taken 

 from near the base of the enamelled crown at PL 69, fig. 3, at the lobe 

 marked b, and the adjoining lobe : the curvilinear diverging extre- 

 mities of the calcigerous tubes terminate in fine cells. The fibrous 

 stinicture of the enamel is very conspicuous in the tooth of the Mos- 

 asaur, the lines to which this structure is due seem to be continued 

 from the peripheral cells of the dentine ; and they bifurcate repeatedly 

 as they traverse the enamel. 



This subdivision of the pulp-cavity, and multiplication of centres 

 of radiation for the calcigerous tubes increase until the piles of 

 dentine can be scarcely distinguished from the Haversian canals of the 

 bone of the jaw with which the root or base of the tooth is confluent. 

 The gradual transition from the simple structure of the compact 

 crown to the multifid dentine of the anchylosed base of the tooth was 

 not known to Cuvier, otherwise he could not have supposed that the 

 crown and the base of the tooth of the Mosasaurus were formed by 

 vital processes of so dissimilar a nature as to forbid him considering 

 them as parts of one and the same body. Cuvier had originally 

 described the expanded base of the tooth of the Mosasaur as the root 

 of the tooth ; but afterwards observing that the corresponding base 

 became anchylosed by ossification of the remains of the pulp with the 

 jaw, he conceived it to be incorrect to regard it as a part of a body 

 which he believed to be an inorganic product, and the result of excre- 

 tion. *' The tooth," he observes, in correcting his first account of the 

 Mosasaurus, '* has no true root, but it adheres strongly to that 

 pulp which has secreted it and it is further held in connection with 

 it by the remains of the capsule which has furnished the enamel, and 

 which by becoming ossified also, and uniting itself to the maxillary 

 bone and the ossified pulp, implants or rivets the tooth with addi- 

 tional force. "(1) 



(1) La dent n'a point de vraie racine, mais elle adhere fortement a ce noyau qui I'a secre- 

 tee, et elle y est encore retenue par le reste de la capsule qui avait fourni 1' email, et qui, en 



