04 Mr. M. C. March on the 



The last worker on the hinge from a taxonomic point of 

 vievv was Bernard. His main work on the subject is found 

 in four papers iu the Bull, de la Soc. Geol. de France, two in 

 the ' Comptes Rendus,' and one in the Ann. des Sci. Nat., 

 Zool. This last paper was the first half of a synopsis of his 

 work, and summed up his views on the Taxodouts and 

 Anisomyarians [Dysodonta, Bernard], and included a sketch 

 of the relationships of the modern and Palaeozoic forms. 

 He died the year of the publication of this first part, and 

 the second part is not recorded as having been published, 

 although he frequently refers to it in the first part. Con- 

 sequently he was unable to publish a classification, although 

 the bulk of the material for it was already published, and he 

 never gave his final views on the relationships of the Taxo- 

 donts and Anisomyarians [Dysodonta, Bernard] to the 

 Heterodonts. For this reason it is necessary to give a short 

 summary of his work, which leads to the adoption of a 

 classification which, although agreeing largely with DalFs 

 in general grouping, yet differs from it fundamentally in the 

 bases of the classes. 



Bernard's main work was confirmed by Munier-Chalmas, 

 and, with the exception of one minor point, by Fischer. 



The most important points of Bernard's work are : — 



1. The tracing of the ontog:enetic development of the 



taxodont teeth in the Taxodonta proper and also 

 in the Anisomyarians. 



2. The tracing of the origin of the taxodont dentition. 



(This was in part done also by Dall, though he did 

 not grasp the bearing of his work.) 



3. The discovery of the existence of an embryonic 



" dentition " in the Taxodonta equivalent to that 

 found in some Heterodonts. 



4. The tracing of the development of the heterodont 



hin^e. 



The Development of Pleurodont [Taxodont and Dysodont] 

 Teeth. 



The taxodont dentition was taken by workers previous to 

 Bernard to differ essentially from the heterodont (Teleo- 

 desmecean, Dall) hinge, in having the teeth developed in a 

 direction esseutiallj perpendicular to the hinge-line instead. 

 o{ parallel to it. Bernard clearly demonstrated that in the 

 prodissoconch stages, and sometimes continuing into disso- 

 conch stages, there is an embryonic " dentition " consisting 



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