PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 8l 



other invertebrates. Whatever may have been the use of the cervical spines in 

 offense or defense, a Hke explanation will hardly account for the greatly elongated 

 dorsal ones. 



The relationships of Edaphosaurus and Dimetrodon, notwithstanding the simi- 

 larity of their dorsal spines, can not be very intimate. The conclusion is irresistible 

 that these resemblances were, for the most part at least, merely the result of con- 

 vergent evolution. We know now that there were other widely different animals 

 in the New Mexican Permian and the European Trias with greatly elongated dorsal 

 spines. All of which render the meaning of their remarkable development still 

 more of a problem. 



Note by Case. — Further confirmation, if such be necessary, has been added to the 

 identity of Edaphosaurus and Naosaurus by the discovery, during the summer of 191 2, by 

 Case of a nearly complete vertebral column of Edaphosaurus (Naosaurus) associated with 

 scapula, pelvis, limb bones, and a broken and fragmentary skull indistinguishable from the 

 type specimen of Edaphosaurus pogonias. Figure 51, a, b, c, shows the occipital region and 

 frontal plate of this skull. It is of interest to add that the humerus possesses an ectepi- 

 condylar foramen as well as an entepicondylar foramen. 



