Third Contribution to the History: Of the Vertebrata of the Permian Formation of Texas
E. D. Cope
Abstract
The preceding paragraphs were written in May of the present year.On my return home, September ist, after an absence of three months, I find that various parts of the skeleton of Periptychus* have reached my museum.On examination, I find that the astragalus of that genus fulfils the anticipation above expressed.Jt 7s without trochica, and nearly resembles that of Hlephas.As it agrees nearly, with that of Phenacodus in other respects I only separate it as a family from the Phenacodontide.One other type remains to be discovered which shall connect the Periptychide and the hypothetical Hyodonta, and that is a Taxeopod without a head to the astragalus,-unless, indeed, the '' Hyodonta'' should prove to have such a head.I think the latter the less probable hypothesis, and hence retain the term Platyarthra for the hypothetical Taxeopod without trochlea or head of the astragalus.These relations may be rendered clearer by the following diagram :TAXEOPODA.