Catalogue of Fossil Fislies. 137 



The fresh-water Siluroid and Cyprinoid fishes, which are the chief 

 forms included in the suborder Ostariophysi, are not known until 

 the Tertiarj' period, but the remains met with in the Lower Eocene 

 are highly specialized, and one Siluroid, at least, cannot be separated 

 from the living Arius. 



The Eels, which are comparatively primitive fishes, showing in 

 many points degenerate specialization, are represented in the 

 Cretaceous rocks by forms displaying most of their peculiarities, 

 except the absence of the caudal fin. Dr. Smith Woodward thinks 

 these fishes could not have been derived from any known form 

 of Teleostean, but must have been directly descended from some 

 Mesozoic ganoid form. 



Nearly all the Cretaceous Acanthopterygian fishes are referable 

 to the Berycoids and Scombroids, and it is among these that the 

 oldest true Acanthopterj'^gian fishes are found. The Upper Cretaceous 

 genera are said to be but little specialized, "and it seems probable 

 that they actually originated at about the period of deposition of 

 the Chalk of the northern hemisphere." Boploptenjx, the genus 

 to which certain species formerly called Beryx are now referred, 

 is remarkable for the excessive development of the mucous cavities 

 about the head. 



The presence of what seems to be a true Percoid fish in the 

 uppermost Cretaceous of France leads Dr. Smith Woodward to infer 

 that many such forms existed during that period, but they still 

 remain undiscovered. Scombroids and Berycoids are found in 

 Tertiary deposits, and " the principal types had already appeared 

 early in the Eocene period ; and among these fishes there are many 

 which cannot be distinguished by their skeletons from genera which 

 still survive." Cod-fishes and flat-fishes date back to the Oligocene 

 and Upper Eocene, but no generalized ancestor has been recognized. 



Dr. Smith Woodward tells us that " as soon as fishes with a complete 

 osseous endoskeleton began to predominate at the dawn of the Cre- 

 taceous period, specialisations of an entirely new kind were rapidly 

 acquired. Until this time the skull of the Actinopterygii had 



always been remarkably uniform in type The pelvic 



fins always retained their primitive remote situation, and the fin-rays 

 never became spines. During the Cretaceous period the majority 

 of the bony fishes began to exhibit modifications in all these 

 characters, and changes occurred so rapidly that, by the dawn of 

 the Eocene period, the diversity observable in the dominant fish- 

 fauna was much greater than it had ever been before. At this 

 remote epoch, indeed, nearly all the great groups of bony fishes, as 

 represented in the existing world, were already difi'erentiated, and 

 their subsequent modifications have been quite of a minor character." 



The author had evidently hoped that the detailed study of the 

 Cretaceous and Tertiary bony fishes would have thrown greater 

 light on the origin of modern forms, for he says " the result, however, 

 is much less satisfactory than might have been expected from the 

 study of animals which lived under conditions most favourable for 

 their preservation as fossils. The circumstance that a very large 



