ACTINOPTERYGII. 119 



There are numerous Cretaceous fishes in which the parietal 

 bones meet partially or completely in the middle line, while 

 the premaxilla is extended so as to exclude a considerable part 

 of the maxilla from the margin of the upper jaw. These 

 appear to be more or less closely related to the existing family 

 of Scopelidac, and some have very delicate skeletons, which 

 may denote a comparatively deep-sea habitat. Some are prob- 

 ably true Scopelidae, such as the fish from the Chalk of West- 

 phalia commonly named Sardinioides monasteri ; but others 

 doubtless represent one or more extinct families, and among 

 these Eurypholis, Enchodus, and Dercetis are particularly note- 

 worthy. 



Sub-Order 5. Apodes. 



Typical eels occur in the Upper Cretaceous of Mount 

 Lebanon, but their generic determination is uncertain, and 

 the specimens are too much crushed to obtain any satisfactory 

 information as to their cranial osteology. Anguilla itself is 

 represented in the Upper Miocene of Oeningen, Switzerland. 



Sub-Order 6. Plectospondyli. 



The physostomous fishes in which there is still a precoracoid 

 arch and a symplectic bone, but in which some of the anterior 

 vertebrae are fused together and there is a chain of ossicula 

 auditus, are chiefly represented in the existing fauna by the 

 CharacinidaD and Cyprinidae. Their palaeontological history, 

 so far as known, is of little interest, the conditions of fossiliza- 

 tion not favouring the preservation of those minute features in 

 their osteology which are of prime importance. Omiodon 

 cabassii, from the Middle Eocene of the Province of Udine, 

 Italy, is claimed to be a Characinoid. Remains of Cyprinoids 

 are not uncommon in freshwater formations above the Eocene, 

 both in Europe and North America. 



Sub-Order 7. Nematognathi. 



The Siluroid fishes (characterized by a precoracoid arch and 

 infraclavicles but no symplectic bone, the anterior vertebrae 

 fused together and modified, and ossicula auditus present) are 



