28 



THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



Branchiosauria the ribs are always straight, heavy, and short, and articulate intra- 

 vertebrally upon a large and strong transverse process. They occur throughout 

 the vertebral column. There is a single pair of sacral ribs which are not to be clearly 

 distinguished from the pre-sacral and post-sacral series. The cervical and caudal 

 ribs are shorter than the dorsal series. The branchiosaurian rib is composed almost 

 entirely of perichondral ossification. It presents the same condition as does the 

 humerus of the cow embryo of 2 to 3 inches in length. The ribs of the branchio- 



FIG. 8. Vertebras and ribs of Amphibia from the Coal Measures of Linton, Ohio. 

 Originals in Geol. Inst. Berlin. (All after Schwarz.) 



A. Caudal vertebra of CEstocephalus remex Cope. Lateral view. X 4. 



B. Caudal vertebra of Ptyonius vinchellianus (?) Cope. Lateral view. X 6. 



C. Dorsal vertebra of Ptyonius pectinatus Cope. Lateral view. X 9. 



D. Notochordal cones and spinal canal of Thyrsidium fasciculare Cope. X 3. 



E. Rib of Molgophis sp. Cope. X 1.75. c = capitulum; / = tuberculum. 



F. Vertebra of Molgophis sp. Cope, from ventral side. X 2. 



G. Dorsal vertebra of Ptyonius pectinatus Cope. From above. X 8. 

 H. Dorsal vertebra of Thyrsidium fasciculare Cope, from below. X 2.5. 



I. Vertebra of Phlegetliontia linearis Cope, from above. X 5.5 



J. Rib of (Estocephalits remex Cope, from posterior dorsal region. X 5. 



K. Dorsal vertebra of Thyrsidium fascicidare Cope, from above. X 1.5 



L. Anterior dorsal vertebra (cervical?) of Thyrsidium fasciculare Cope. Lateral view. X 1 .5. 



M. Vertebra of Phlegethontia linearis Cope, from side. X 5. 



saurs are identical in every way with the ribs of modern salamanders and form one 

 of the strong arguments in favor of the relationship of the Branchiosauria to the 

 Caudata. Among the Microsauria the ribs are always long, slender, curved, and 

 intercentral. They may be either single or double headed, but usually the former. 

 They resemble in their characters the ribs of some of the early reptiles and an 

 attempt has been made to relate the Microsauria (469) to the primitive reptiles on 

 this basis. The ribs of the other groups are still unknown. Indeed, representatives 

 of the Temnospondylia and the Stereospondylia are very scanty in the American 



