Sir P. Egerton on Fossil Fishes from Southern India. 91 



unmixed with doubts of the stability of the generic and specific characters as at pre- 

 sent acknowledged in the ' Poissons Fossiles.' Agassiz has himself complained of 

 the paucity of materials for arriving at any very definite conclusions as to the 

 variations of form in the teeth occurring in the various positions in the mouth of 

 the same species. Those naturalists who have studied the recent Sharks are well 

 aware of the extent of those variations in a single individual, and can, therefore, 

 appreciate the difficulties under which Agassiz has laboured in attempting a sy- 

 stematic arrangement of the fossil Squaloids. As I am in hopes this distinguished 

 ichthyologist will shortly have an opportunity of examining the Indian collections, 

 I offer the following descriptions as provisional rather than final ; or, at all events, 

 as giving the characters of forms in themselves distinct, but which may hereafter 

 be grouped together under legitimate generic and specific denominations. 



Cycloid Order. 



Scomberoid Family. 



Enchodus serratus, Eg. — Three teeth from the Pondicherry beds evidently be- 

 longing to the genus Enchodus. As I have before stated, they bear a very close 

 resemblance to the species figured by Agassiz as Enchodus halocyon ; at the same 

 time (although the materials are too defective to warrant any definite conclusion), 

 there are appreciable discrepancies of sufficient importance to induce me to abstain 

 from identifying the Indian teeth with the species alluded to. The most perfect 

 specimen, as compared with teeth of similar size of E. halocyon, presents the fol- 

 lowing distinctive characters. The surface of the enamel is more smooth and even, 

 in consequence of the fineness of the longitudinal striae, which in E. halocyon are 

 coarse and strongly marked. The transverse bands are broader, and the form of 

 the teeth is less attenuated. The most important feature it presents is in the 

 finely serrate cutting edge, which in all the specimens I have seen of E. halocyon 

 is smooth and entire. A second fragment corresponds in all these points. The 

 third specimen is a smaller tooth, and only differs from E,. halocyon in the smooth 

 and highly polished surface of the enamel. None of these teeth are perfect. The 

 length of the largest is half an inch, of the smallest two lines. 



