6 CRETACEOUS AND TERTIARY FISH. 



to the diagnoses of the higher groups and generic synonymy. 

 The writer is indebted to the Academy of Natural Sciences of 

 Philadelphia, for the use of its library and collections, where 

 most of this work was carried on. I am also under obligations 

 to Dr. Henry B. Kiimmel, the State Geologist, for the oppor- 

 tunity of consulting the collections of the State Geological Sur- 

 vey. All the figures are natural size, unless otherwise stated, 

 in which case the reduction is shown by a line which indicates 

 an inch. The material from the Geological Survey collections is 

 indicated in the explanation by a *. 



