4<o6 



THE DEVONIAN PERIOD 



ancient group of which but two representatives remain at present, 

 both of them African. These fishes, like the Dipnoans, have 

 "lobate " paired fins (see Fig. 144), i.e. the part of the fin belong- 

 ing to the internal skeleton is large and covered with scales, form- 



FlG. 143. — Coccosteus decipiens. (Dean, after Smith Woodward.) 



ing a lobe to which the fin-rays are attached. Most of the 

 Devonian members of the group have massive rhomboidal scales, 

 but in others, like Boloptychius, the scales are thinner, rounded, 

 and overlapping. 



The most advanced fishes of the period are the Ganoid mem- 

 bers of the Actinopterygians, which from the Devonian until 



Fig. 144. — Holoptychius Andersoni. (Dean.) 



nearly the end of the Mesozoic era continue to be the dominant 

 type of fishes. Nearly all of them have thick, shining scales of 

 rhomboidal shape. 



The Devonian fish fauna (using that term in a very comprehen- 

 sive sense) is thus seen to be a rich and varied one, includ- 



