28 



The Ganoids 



the Triassic and Jurassic. The fins are fringed with fulcra, 

 the scales are ganoid and rhombic, and the vertebras reduced 



FIG. 19. Caturus elongatus Agassiz. Jurassic. Family Isopholidce. (After Zittel.) 



to rings. The mouth is large, with small teeth, and formed as 

 in the Isospondyli. The caudal is scarcely heterocercal. 





FIG. 20. Notagogus pentlandi Agassiz. Jurassic. 



(After Woodward.) 



Family Macrosemiidce. 



Of Pholidophorus, with scales joined by peg-and-socket joints 

 and uniform in size, there are many species. Pholidophorus 



FIG. 21. Ptycholepis curtus Egerton. Lias. 

 (After Woodward.) 



Family Isopholidce. 



latiusculus and many others are found in the Triassic of England 

 and the Continent. Pholidophorus americanus occurs in the 



