ORDER ELASMOBRANCHEI. 



941 



Orodus. Most of these spines (fig. 852, 2) are, however, referable 

 to the allied Carboniferous genus Sphenacanthns ; and they are 

 characterised by their ornamentation of robust longitudinal ridges, 



Fig. S64. — Upper jaw of the Port Jackson Shark {Cestracion Philippi). One-half natural 

 size. (After Owen.) 



which are partly nodose. Other Carboniferous genera are Campodus, 

 Diditodus, and Tristychius, some of which have several synonyms. 

 In the Thuringian Permian this family is represented by the genus 

 Wodnika, in which the teeth have large and smooth crowns well 



Fig. 865. — Tooth of Hy- 

 bod?cs raricostatus ; from 

 the Lias of Dorsetshire. 

 (After S. Woodward.) 



Fig. 866. — Imperfect fin-spine of Hybodus (cf) b as anus ; from 

 the Lower Cretaceous. Reduced. 



adapted for crushing ; while in the Muschelkalk, or Middle Trias, 

 we have the imperfectly known Palczobatis, with teeth very like those 

 of Aster acanthus. With the genus Hybodus, ranging from the Mus- 

 chelkalk to the Lower Greensand of Europe, we come to a type 

 which is now almost as well known to us as existing Sharks, owing 



