Eastman: Tertiary Fish-Remains. 377 



Enchodus I ?) sp. 



\ small sized species which may be provisionally referred to this 

 genus, but the precise relations of which cannot be determined with 

 certainty, is indicated by the greater part of the caudal region ami 

 tail of a single individual, as shown in Plate XXIV, fig. i. The form 

 of body, as far as can he inferred from the portion preserved, is very 

 similar to that of E. longidens (Pictet), from the Upper Cretaceous of 

 Mount Lebanon, ami it agrees also in size with the latter. The 

 caudal fin in the African form is longer and more deeply furcate than 

 in the Syrian species, and the dorsal fin is more remotely situated. 



In the solitary specimen under examination more than a score of 

 vertebrae are seen to be preserved in natural sequence, but it is im- 

 possible to tell whether these constitute the entire number of caudals, 

 for the reason that the anal fin is not shown in its entirety. Of the 

 dorsal only about ten of the widely spaced fin-supports, and the 

 distal extremities of a few finely articulated fin-rays are to be seen. 

 A few intermuscular bones are preserved above and below the axis, 

 and the structure of the vertebral centra together with their spinous 

 processes, and the relations of these latter to the median fin supports 

 (interneurals and interhaemals) are in harmony with our determination 

 of this species as belonging to the genus Enchodus, or to some closely 

 related form. The remote position of the dorsal, its comparatively 

 feeble fin-supports, and short caudal peduncle prevent an assignment 

 of this species to the genus Diplomystus. The fact that Enchodus 

 is an Upper Cretaceous genus must be granted some weight in ascribing 

 the age of the fish-bearing beds at Benito to the early Tertiary. 



We may conclude this paper with a few general remarks concerning 

 Diplomystus, and other related doubly-armored herrings. True 

 Clupeoids first appear at the beginning of the Cretaceous, and are 

 probably descended from typical Jurassic Leptolepids, as indicated 

 by their closely similar skeletal structure. The acquisition of enlarged 

 ridge-scutes along the ventral margin, a character peculiar to Clupca 

 and its allies, dates from the Lower Cretaceous, and toward the close 

 of that period forms had become introduced and attained a wide 

 distribution which possessed dorsal ridge-scutes as well as the ventral 

 series. These are marine species, from Asia Minor, southern Europe, 

 and Brazil, belonging to the genus Diplomystus. In North America a 

 number of fresh-water species are found as early as the Middle Eocene. 



