EARLIEST KNOWN FISHES 



163 



From this type there radiated many others: {B) the deep, 

 narrow-bodied fishes of relatively slow movements, frequenting 

 the middle depths of the waters ; {D) the swift-moving, elongate 



DEPRESSED (GROVELINGI 



Fig. 44. The Yive Principal Types of Body Form in Fishes. 



These begin with {A) the swift-moving, compressed, fusiform t3'pes which pass, on the 

 one hand, into {B) laterally compressed, slow-moving, deep-bodied types, and, on the 

 other, into (C) laterally depressed, round, bottom-dwelling, slow-moving types, also 

 into (D) elongate, swift-moving fusiform types which grade into (£) the eel-like, swift- 

 moving, bottom-living types without lateral fins. These five types of body form in 

 fishes arise independently over and over again in the various groups of this class of 

 vertebrates. Partially convergent forms subsequently appear among amphibians, rep- 

 tiles, and mammals. Prepared for the author by W. K. Gregory and Erwin S. Christman. 



