52 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 9i 



The presence of a form apparently representing Haploconus in 

 beds nearly as old as Puerco is interesting in extending downward 

 the known range of Haploconus and tending to a rather limited 

 extent to break down certain of the characters separating Haploconus 

 and Conacodon. Conacodon possesses specialized dental structures 

 which apparently did not give rise to those seen in Haploconm^^ but 

 this earlier form of Haploconus^ as represented in the Wagonroad 

 fauna, shows a less marked separation from the Puerco Conacodon 

 than do the Torre j on species. 



LITERATURE CITED 



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