4 86 



TUBE-BLADDERED GROUP. 



within reach. Its flesh is of poor quality. It has been considered that the extinct 

 Chiromystas, from the Eocene of Brazil, may belong to this family. 



Long-Finned Herring, — Family Bathythrissid^e. 



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, 

 Saueocephalid.e, 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 

 saurodont fishes. 

 The first family 



(Dercetidce) is typified by the genus 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 (EncRodontidce) 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 Saurocephalws, 

 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 m 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 

 Australian Cretaceous genus Portheus being distinguished by the presence of an 

 enormous bony crest in the middle line of the skull. 



SKELETON OF A SAURODONT FISH (Eurt/phoHs). 



