SYNOPSIS OF THE VERTEBRATE FAUNA OF THE rUEItCO SERIES. oOO 



ganus, Onychodectes, Miocljv3nus, Chriacus and Dissacus are made, and they throw 

 considerable light on the phylogeny of the various genera. It is apparent on all 

 grounds that MioclaMnis is the central type of Creodonta for the Puerco Epoch, and 

 that all other types of the suborder may be traced to it as derivative, either by pro- 

 gressive 01" retrogressive specialization. Thus the line which our present knowledge 

 ends with Hemiganus, is one of simplification and reduction of the molar dentition at 

 the expense of increase in the development of the canine dentition, as takes place in 

 the line of the seals. In the line of the Mcsonychid:c another kind of simplification of 

 the molar dentition of the inferior series appears, and the feet undergo specializa- 

 tion, apparently in accordance with the needs of a terrestrial life. A third line 

 leading towards the Oxya'uidiB commences with the genus Chriacus, which is easily 

 modified into Stypoloj)hus on the one hand and Deltatherium on the other, the latter 

 having some special characters of its own, and forming probably the end of its line. 

 The line which gives us Miacida', and in Miocene times the Carnivora, probably 

 diverged from a Miochenus, but from a species of an earlier horizon than the Puerco, 

 since two species of Didymictis are already contemporai'ies with the Miochenus of 

 that age. These relations may be displayed as follows : 



Carnivora Oxymnidm 



/ 



Didymictis Deltatlicrium Stypolophus 



Miacis Chriacus 



Mioclicnus 

 Triisodon Onycliodecles 



Dissacus Conoryctes 



PachysDna Ilemiganus 



/ 

 Mesonyx 



In the reference of these genera to families, lack of information as to ceitain 

 parts of the structure forbids liiial C()iK;lusi()ii>. Leaving aside the JNEiacida' and 

 0.xytcnida\ we find that tliu I'roviverridiu (Schlosser, Leptictida-, I'iv. II, (Jopf ) cm- 



