THE FOSSIL FISHES OF THE CHALK.
205
are at the present day. The Ctenothrissidae of the Chalk,
already mentioned, also show more resemblances to the primitive
Acanthopterygii than any Clupeoids of later times.
Finally, it may be observed that the eels also appear first
Fig. 6. Hoplopteryx lewesiensis, Mant.
Fig. 7. Hoplcpteryx affinis, Gunther.
in the Upper Cretaceous formations, and are represented by
fragments of Urenchelys in the English Chalk. Complete speci-
mens of these fishes from the Lebanon show that at first they
had a large rounded tail-fin. They have all lost this appendage
since the Cretaceous period, and those members of the group