28 The Ganoids 
the Triassic and Jurassic. The fins are fringed with fulcra, 
the scales are ganoid and rhombic, and the vertebre reduced 
Fie. 19.—Caturus elongatus Agassiz. Jurassic. Family Isopholide. (After Zittel.) 
to rings. The mouth is large, with small teeth, and formed as 
in the Isospondyli, The caudal is scarcely heterocercal. 
Fic. 20.—Notagogus pentlandi Agassiz. Jurassic. Family Macrosemiide. 
(After Woodward.) 
Of Pholidophorus, with scales joined by peg-and-socket joints 
and uniform in size, there are many species. Pholidophorus 
Fic. 21.—Ptycholepis curtus Egerton. Lias. Family Isopholide 
(After Woodward.) (eG 
latiusculus and many others are found in the Triassic of England 
and the Continent. Pholidophorus americanus occurs in the 
