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TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



Eocene (Woodward)). The family Elopidae, as recognized by Woodward (1901, Pt. IV, 

 p. 7; 1907, p. 112), falls into two sections: the first is characterized by the fact that the 

 parietals meet above the supraoccipital, which has, however, already extended forward 

 some distance beneath the parietals. This section includes Elops, Megalops and several 

 Cretaceous genera. All these Cretaceous genera resemble the existing Elopidae and each 

 other in their generally primitive isospondyl skeletal characters. They show also the transi- 

 tion from the leptolepid to the isospondyl stage in the evolution of the hypural bones of 

 the tail, three of which in Spaniodon are beginning to be expanded. The chief differences 



Leptoiepis dubius 



Fig. 30. Leptoiepis dubius. After Smith Woodward. 



among these genera are in the characters of the teeth and jaws: Elopopsis was evidently a 

 predaceous form with large mouth and large teeth; Osmeroides had minute teeth and 

 smaller mouth. In the existing genera the teeth are very minute and clustered on the 

 margins of the rather large mouth. 



In the second section of the family (which does not appear to be either closely related 

 to the first group or very homogeneous in itself) the parietal bones are relatively small and 

 do not meet above in the mid-line but are definitely thrust apart by the supraoccipital. 

 In this division fall the genera Thrissopater, Spaniodon and several others. In Thrissopater 

 the small conical teeth extend right to the distal end of the long and slender maxilla, as 

 they do in the existing anchovy [Engraulis) among the clupeoid fishes and in the Gonos- 

 tomidae and other deep-sea isospondyls. 



The skull of Elops, as figured by Ridewood, is more primitive than that of the tarpon 

 in not having a strongly upturned mouth but is otherwise fundamentally similar. The 

 tarpon skull (Fig. 31) is notable for its depth in the opercular region and for the marked 

 uptilting of the nearly edentulous jaws. This is brought about through the relative 

 shortness of the snout and the depth and forward position of the quadrate-articular joint. 



