FOSSIL CROSSOPTERYGIANS i$i 



the caudal. In these forms a number of paired gular 

 plates may occur. 



In a closely related genus, Eustkenoptcron, also of 



Fig. 151 



152 



Fig. 151. Gyroptychius. X \. Old Red Sandstone, Scotland. (After SMITH 

 WOODWARD.) 



Fig. 152. Osteolepis. X 4. Old Red Sandstone, Scotland. (Restoration 

 from SMITH WOODWARD, after PANDER.) 



Devonian age (Fig. 154, A, B), the structure of the basal 

 parts of the unpaired fins is exceedingly interesting ; the 

 radial supports are unfused, while the basals, merged in a 



Fig. 153. Holoptychius andersoni. Old Red Sandstone, Scotland. 



single plate, have come into especial relation with the 

 axial skeleton ; the subsequent stage of their differentia- 



