362 



PALAEONTOLOGY OF OHIO. 



four superior branchihyals, 6/ 6", are supported by corresponding inferior 

 or hsemal branchihyals, hv', bv", and these in turn are articulated each 

 to its proper axialhyal, ah", ah'". The absent elements are the two axial 

 and two hsemal elements, which exist as supports of the posterior two 



Fig. 7. 



NXCXUBUB HACULiTUS. 



superior branchihyals, b"', b"",in the fishes. In the branchiferous Nec- 

 turus macvlatus a considerable modification ensues. The four superior 

 branchihyals are present, but according to Fischer the first and second 

 are confluent, and are supported by confluent hsemal elements. (See fig. 

 6, b' 6" and bv' bv".) A third inferior branchihyal is added. If we now 

 turn to the air-breathers, Protonopsis (fig. 7), we obserye a marked pecu- 

 liarity. The third hsemal branchihyal remains, while the second is con- 



