118 



NEW YORK ZOOLOGICAL SOCIETY. 



COPPERHEAD, ANCISTRODON CONTORTRIX 



on ichthyology. It is often important to ascertain the num- 

 ber of vertebrae in fishes for purposes of classification, and 

 these can usually be counted without difficulty in a radiograph. 

 The natural curve of the backbone — seldom seen correctly in 

 prepared skeletons of fishes — is well shown. The character of 

 the caudal vertebrae showing the heterocercal or homocercal type 

 of tail is seen very clearly. The radiograph is really a shadow 

 picture made with the object laid flat upon the dry plate, the oste- 



