7 



PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



With differences that can hardly be accounted of generic value elsewhere in the skeleton, 

 it would be idle to claim for the greater spinous expansion of Dimetrodon a family value in 

 their classification. Whence it follows that in the strict application of the laws of priority, 

 the family name Sphenacodontid<E (Marsh, May 3, 187S) must take precedence over Clepsy- 

 dropidce (Cope, May 8, 1878), pro\'ided no question of scientific rectitude on the part of 

 its author is raised. 



Fig. 45. Sphenacodon ferox Marsh, X %. A, ventral surface of a right humerus, 

 No. 818, Yale University; B, ventral surface of right femur, X % 



