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Notices of Memoirs — M. Dollo — Dinosaaria. 



but one is afforded by tbe remarkable teetb from the Upper Cretaceous 

 (Senonien) described by M. Dollo under tbe name of Craspedodon 

 lonzeensis (Diagram C), in wbicb, in addition to antero-posterior 



Diagram C. — Tooth of Craspedodon lonzeensis. Fig. 1 from the enamelled 

 surface, f > c crown, d f cingulum, the letters a b e g hh I indicate the 

 serrations and ridges. Fig. 2 in profile, f. Fig. 3 the large and small 

 serrations more magnified. Fig. 4 section at x y, f • 



serrations, tbere are primary, secondary, and tertiary lateral ridges, 

 of wbicb both primary and secondary are serrated. Finally tbe 

 American Cionodon simulates tbe dentition of Ungulate Mammals in 

 having numerous cheek-teeth in use at one and the same time. 



M. Dollo concludes this interesting survey by observing that " it 

 appears that while the specialization of the dentition in the Ungulata 

 has taken place either by the development of infoldiugs in the 

 enamel (Equidce), or by the multiplication of tubercles (Suidce), accom- 

 panied by gradual elevation of the crown, it has manifested itself in 

 the herbivorous Dinosauria by the development of ridges and 

 serrations, or by the simultaneous use of numerous teeth. While, 

 however, the cause of the evolution of the dentition of the Ungulata 

 is, so to speak, known to us, we can only guess at that of the dentary 

 system of the great Eeptiles which filled their place during the 

 Secondary epoch." R. Lydekker. 



