CARBONIFEROUS AGE. 



301 



Under Vertebrates, there were both Fishes and Amjihibians. The 

 Fishes were either Ganoids or Selachians ; and the latter embraced 

 large numbers of the Cestraciont kind, having great bony plates in 

 the mouth, for mastication. Fig. 600 represents, natural size, one 

 from a large species, of the genus Cochliodus, from Illinois. The posi- 



Figs. 600, 600 A 



600 



Teeth of Cestraciont Sharks. 



Fig. 600, Cochliodus nobilis ; 600 A, C. contortus (X %)- 



tion in the mouth is shown in Fig. 600 A, representing, one third 

 the natural size, the jaw of a foreign species. The teeth of other 

 sharks, called Hyhodonts, are shown in Figs. 601 to 603. These also 



Figs. 601-603. 



Teeth of Sharks 



Fig. 601, Carcharopsis Wortheni ; 602, Cladodus spinosus ; 

 miliaria. 



, Orodus mam- 



Were numerous. Large fin-spines of some of the Sharks have been 

 found in the rocks, one of them eight inches long. 



Footprints of Amphibians have been found at a few localities in 

 American Subcarboniferous rocks. A reduced view of a slab from 

 near Pottsville, Pennsylvania, is shown in Fig. 604. There is a suc- 

 cession of six steps, along a surface little over five feet long : each 

 step is a double one, as the hind-feet trod nearly in the impressions 



