740 THE EOCENE FAUNA. 



While the above scheme defines the groups exactly, and, so far as can 

 now be ascertained, naturally, I do not doubt but that future research 

 among the extinct forms will add much necessary information which we do 

 not now possess. It is possible that the group I called Mesodonta may yet 

 be distinguished from the Insectivora by characters yet unknown. But I 

 cannot admit any affinity between this group and any form of " Pachy- 

 derms," as suggested by Filhol, or of Suillines, as believed by Lyddeker.^ 

 Such suppositions are in direct opposition to what we know of the phylogeny 

 of the Mammalia. These views are apparently suggested by the Bunodont 

 type of teeth found in various Mesodonta, but that character gives little 

 ground for systematic determination among Eocene Mammalia, and has 

 deceived paleontologists from the days of Cuvier to the present time. The 

 only connecting point where there may be doubt as to the ungulate or 

 unguiculate type of a mammal is the family Periptychidce, of the suborder 

 Condylarthra. The suborder Hyracoidea may furnish another index of con- 

 vergence. 



The families included in these suborders will be the following: 



T^NIODONTA. Calamodoniidw ; Ectoganidw. 



T[LLODONTA. Tillotheriidw. 



Daubentonioidea. Chiromyidw. 



Prosijii^. TarsiidcB; (?) Anaptomorphidce ; (?) Mixodectidw ; Lemuridw. 



Insectivora. Soricidce; Erinaceidce; MacrosceKdidw ; Ttipceidte; Adapidce;^ Arcto- 



cyonidw. 

 Creodonta. TalpidcB; Chrysoclilorid(e ; Esilionycliidce ; Centetidce {=Leptictidce oMm); 



Oxi/anidw ; Miacidte ; Amblyctonidce; Mesonychidce. 



I at one time called this order by the name Insectivora, a course which 

 some zoologists may prefer. But a name should as nearly as possible 

 adhere to a group to which it was first applied, and whose definition has 

 become currently associated with it. Such an application is correct in fact, 

 and is a material aid to the memory. There are various precedents for the 



■Memoirs Geological Survey India, Ser. x, 1883, p. 145. 



-Two species of PeJjicodus must be removed from this genus and family, and be placed in the 

 Creodonta with Mioclanuis. They are the P. pelridens and P.angulaius, which have the posterior inner 

 tubercle of the superior molars, a mere projection of the cingulum. I place them in a new genus, which 

 diiiers from Mioclcsnua in the possession of an internal cusp of the fourth inferior premolar, under the 

 name of CAriacMs; type, C. pelvidens. 



