PALEOZOIC TIME — CARBONIC. 



681 



nearly three long and two broad. The figure of the latter represents, 

 reduced, only a small portion of the specimen ; as figured by Newberry the 

 spine has five teeth ; when entire it was probably 18 inches in length, and 

 occupied, along the body of the Shark, according to jS'ewberry, the place of 

 the posterior dorsal fin. It could thus rip open its prey when swimming 

 underneath it, and slash effectually in defense. 



Amphibians. — Besides footprints, which thus far are the only evidence 

 of Amphibians in the Subcarboniferous, the Coal-measures have afforded 



1106-1107. 



FrN-SPDfES OF Shakes. — Fig. 1106, Edestus giganteus ; 1107, E. minor (each x^). Newberry. 



remains of skeletons. They show that many of the earlier kinds were much 

 like their predecessors, the higher Ganoid and Dipnoan Fishes, in having a 

 bony cranium instead of one with large open spaces and little bone, like the 

 modern Frog ; and in allusion to the ivell-roofed head, they are called Stegocephs 

 by Cope. Among modern Amphibians only some snake-like kinds have a 

 similar cranium. They are also like the Fishes in their teeth, the most of 

 them having the enamel inflexed along the surface grooves, producing the 

 Labyrinthine texture which suggested for the species the name of Lahyrintlio- 

 donts. Further, they generally have biconcave vertebrae, like Fishes. 

 Moreover, the Amphibians occur of all grades from (1) Snake-like forms 

 without limbs, to (2) those with feeble swimming organs ; and thence to 

 (3) the four-limbed species of various sizes, up to kinds as large and formid- 

 able as Alligators. It is interesting to note also that the feet have five toes 

 (or less), and the fingers the modern number of bones. 



The Coal-measures of Ohio, at Linton, afforded Newberry numerous 



