The Spine-finned Teleostei 373 



ously referred to the Percidae or the Berycldae or even 

 made into a separate family, but which from the studies 

 of Starks is most probably a percoid, and finally the varied 

 genera of the Percidae. It may be well then to look, more 

 closely into their affinities and nearest allies. 



The Salmonidae, evidently closely allied to and de- 

 scended from freshwater Clupeidae like Diplomystus of 

 early Eocene rocks, are only known by fossil remains from 

 the Miocene onward. But the brittle and destructable char- 

 acter of salmonid bones probably explains their absence 

 from earlier strata, such as the Upper or Mid-Cretaceous. 

 The Percopsidae are unknown in the fossil state, but the 

 two genera Percopsis and Columbia, both native to rivers 

 of N. America, are truly annectant between soft and hard 

 spined types. So Jordan says (255:241) "Two species 

 only are known among living fishes, these emphasize more 

 perfectly than any other known forms, the close relation 

 really existing between spinous and soft-rayed forms. The 

 single family of Percopsidae would seem to find its place 

 in Cretaceous rocks, rather than in the waters of to-day." 

 The existence of mucous cavities in the bones of the head 

 of these, at once suggests possible affinity with such percoids 

 as Acerina. 



Aphredoderus, represented only now by one living 

 species, found in streams of the Mississippi valley, was 

 undoubtedly once represented by abundant freshwater an- 

 cestral fishes in Eocene lakes of N, America. For Cope 

 has described Amphiplaga, Asineops, Erismatopterus, and 

 TrichopJianes, from the Green River Shales or from the 

 Florissant beds of the Western States. In these the dorsal, 

 pelvic, and anal fins all show one to three anterior spines. 

 The transition from the last to the varied genera of the 

 Percidae is an easy one, and doubtless also was in evolu- 

 tionary continuity. 



So the writer would accept it, that from primitive fresh- 

 water clupeoid and salmonid ancestry of early Cretaceous 

 to Eocene age, and probable American habitat, three more 

 or less divergent lines arose. One of these now ends in the 

 highly modified Pantodontidae of West Africa, another, 

 that early became a marine derivative, gave origin to the 



