2 University of Michigan 



this form is the development of greatly elongated neural spines 

 with prominent lateral projections on all the pre-sacral verte- 

 brae. This peculiarity led to the identification of the first 

 fragments of the spines as bits of petrified branches; later 

 when their true nature was made out Cope described the ani- 

 mal as Naosaurus, the Ship-lizard, from the fancied resem- 

 blance of the cross-bars on the spines to the yard-arms of a 

 ship. For a long time, when the skeleton was only imperfect- 

 ly known, it was supposed that the animal was carnivorous 

 in habit because of the general resemblance of the known 

 bones to those of the carnivorous genus Dimetrodon with 

 elongated, but smooth, spines. It was finally shown that the 

 skull of a herbivorous or molluscivorous form previously de- 

 scribed as Edaphosaurus really belonged with the cross-barred 

 spines and the long used name Xaosaurus was necessarily 

 abandoned. 



The skeleton as now mounted shows an animal with a rela- 

 tively small skull provided with sharp conical teeth on the 

 edges of the jaws and strong plates filled with blunt, crushing 

 teeth on the dentary bones and the palate. The dorsal spines 

 rise abruptly from just back of the skull to a considerable 

 height and then curve back over the pelvic region. The sacral 

 spines are abruptly shortened. The spines of all the pre- 

 caudal vertebrae are provided with cross-bars. The lower 

 pair are prominent and probably marked the upper limit of 

 dorsal muscles ; above this pair the cross-bars are rapidly re- 

 duced in size until above the center of the length of the spine 

 they are reduced to knobs and lose the paired arrangement. 

 The spines in the species E. cniciger terminate in blunt points. 

 In other species of the same genus the shape of the spines and 

 the size and arrangement of the cross-bars are notably dif- 

 ferent. 



