The Soft-finned Teleostei 349 



Cretaceous fish-fauna will be revealed than that now known. 



Meanwhile the somewhat curious anomaly exists, that 

 while several large groups of the most primitive freshwater 

 fishes structurally, do not appear till in latest Cretaceous 

 or early Eocene age, a few freshwater ones but many 

 marine ones appear from the Neocomian and Gault up- 

 wards. We would explain the apparent anomaly by con- 

 sidering that numerous representatives of the large fresh- 

 water teleost families Characinidae, Cyprinidae, Gymnoti- 

 dae, Siluridae and Loricaridae amongst others, were rapid- 

 ly evolving from more primitive "ganoid" ancestors, but 

 failed to leave traces of their remains, or more likely have 

 as yet been overlooked in freshwater Cretaceous and Eocene 

 strata. 



Our reasons for the above positions are : (a) that where 

 such strata have been recognized and studied, as with the 

 Laramie, the Wasatch, and the Bridger beds of Western 

 America, an abundant freshwater teleost fauna is encounter- 

 ed as Cope and others since have demonstrated; (b) the 

 latest Cretaceous or earliest Eocene representatives of the 

 great morphological group Ostariophysi, already have the 

 delicate auditory arrangements perfected, that caused Cope 

 and Sagemehl to view them as a closely related series. So 

 a considerable period of time must have elapsed, between 

 commencing evolution of the Ostariophysi from some 

 ganoid ancestor devoid of such auditory arrangements, 

 and the perfected condition of it in the typical group; (c) 

 the world-wide distribution of the Ostariophysi in fresh- 

 waters, and the high adaptation of many genera to special 

 freshwater areas, compel us to recognize that the group had 

 been evolving in special areas, through a long period of 

 time. 



The families Characinidae and Gymnotidae, the Cypri- 

 nidae, the Siluridae, and the Loricaridae will now be treated 

 in succession. In their gradual evolution, three diverging 

 groups evidently started from one or a few primitive an- 

 cestral species. The Characinidae — with the Gymnotidae 

 as a highly specialized offshoot from it, or from between 

 it and the Siluridae — spread steadily over Gondwana land, 

 from some ancestor that, tentatively and with complete 



