4 86 
TUBE-BLADDERED GROUP. 
within reach. Its flesh is of poor quality. It has been considered that the extinct 
Chiromystus, from the Eocene of Brazil, may belong to this family. 
Long-Finned Herring,—F amily Bathythrissidje. 
Although its osteology has not apparently been described, we may place here 
the fish ( Bathythrissa dorsalis ) shown in the illustration on p. 485, which is 
another of the numerous forms in the present section representing a family by 
itself. Having an oblong body, with a rounded under surface, invested with 
cycloid scales, the head naked and devoid of barbels, and no fatty fin, this fish may 
be at once recognised by the great length of the many-rayed dorsal fin, which 
occupies nearly the whole length of the back, and is situated in advance of the 
short anal. There is no air-bladder, and very small eggs are produced by the 
ductless ovaries. This fish, which attains a length of two feet, has been obtained in 
Japanese waters at a depth of between three and four hundred fathoms. 
The Extinct Saurodonts, —Families Enchodontid^e, 
Baurocephalidae, etc. 
Before proceeding to the consideration of the herrings, we may briefly refer 
to a group of more or less closely allied extinct families, mainly characteristic of 
the Cretaceous period, but also represented in the lower Tertiaries. From the 
large size of their 
lanciform, reptile¬ 
like teeth, all the 
■ members of the group 
are collectively 
spoken of as the 
7 7 .. saurodont fishes. 
SKELETON OF A SAURODONT FISH (Eurvpholis). 
The first family 
(Bercetidce ) is typified by the geuus Dercetis, of the Chalk, and is characterised by 
the elongated form of the body, the large size of the teeth, which are implanted in 
sockets, and the presence of several rows of large triangular bony plates along the 
sides of the body ; the muzzle being frequently produced into a beak, and the dorsal 
fin single. Nearly allied is the family ( Encliodontidce ) represented by the widely 
spread Cretaceous genera Enchodus and Eurypholis ; these fishes having the body 
moderately compressed, and either naked or partially protected by bony plates, 
and the elongated upper jawbones armed (like those of the lower jaw) with small, 
immovably welded teeth. To a third family belongs the genus Saurocephalus, 
from the North American Cretaceous, which, together with the allied forms, has 
the body much compressed, the large upper jaw armed with powerful teeth, usually 
set in sockets, and a single series of similar teeth in the lower jaw, the palatine 
bones being toothless. A peculiarity of the vertebrae of these fishes, with the 
exception of those of the neck, is the presence of two deep grooves and pits on 
their sides. Some of these fish attained huge dimensions; the American and 
Austi alian Cretaceous genus Povtheus being distinguished by the presence of an 
enormous bony crest in the middle line of the skull. 
