376 Evolution and Distribution of Fishes 



Ctenothrissidae, another and for our present purpose im- 

 portant, line, leads from Percopsis and Columbia, through 

 the Aphredoderids to the percoid types. 



If such a related series as the writer has presented, is 

 appropriate and evolutionarily correct, it should probably be 

 possible to trace a fairly continuous line of descent, along 

 with possible side-lines for the entire series of spiny-finned 

 teleosts, as descended from soft-finned forms, which in turn 

 were derived, as now commonly accepted, from a ganoid 

 ancestry. The series of illustrations on p.p. 374,375 sets 

 forth what the writer would present as a possible outline 

 grouping of such a phylogenetic continuity. 



From Cretaceous clupeoid and salmonid ancestors then 

 of Cretaceous age we would consider that the Percopsidae 

 arose, and these again originated the Aphredoderidae. But 

 already during late Cretaceous and early Eocene time the 

 last were evolving into a group of freshwater genera from 

 which sprang the Centrarchidae and Percidae, and into a 

 group of marine genera that evolved as the Beryciformes, 

 and the nearly allied Scombriformes. The Perciformes in 

 turn gave rise to such important freshwater families as the 

 Cichlidae, the Nandidae, the Serranidae and the Lobotidae, 

 the two latter of which in turn gave off genera that passed 

 seaward and became modified derivative genera. 



But, as will be fully described later on, the Chaetodonti- 

 formes, the Scorpaenidae, and the Gobiiformes again sepa- 

 rated off as seaward derivatives of the Percidae, and then 

 evolved into the varied, often highly modified and some- 

 what degraded, fishes that will be referred to below. 



To compare now somewhat closely the constitution of 

 salmonid-percopsid and derivative fish-fins, the first of these, 

 Prototroctes shows (Fig. 58) an adipose dorsal fin, the 

 soft-fin rays of the main dorsal fin are 12, the anal rays are 

 8, and those of the ventrals are 8. The position of the 

 ventral fins is between the vertical line of the dorsal and the 

 pectorals. In Percopsis (Fig. 59) there are 2 spines and 9 

 soft rays in the dorsal fin, i or 2 spines and 7 soft rays in 

 the anal, and one spine also 8 soft rays in the ventrals. 

 In Columbia (Fig. 60) there are 2 spines and 9-10 soft 

 rays in the dorsal fin, 2 spines and 7-8 soft rays in the anal. 



