The Crossopterygil 229 
The Holoptychiide have the pectoral fins acute, the scales 
cycloid, enameled, and the teeth very complex. Holoptychius 
nobilissimus is a very large fish from the Devonian. Glyptolepis 
leptopterus from the Lower Devonian is also a notable species. 
Dendrodus from the Devonian is known from detached teeth. 
In the Ordovician rocks of Canon City, Colorado, Dr. Wal- 
cott finds numerous bony scales with folded surfaces and stellate 
ornamentation, and which he refers with some doubt to a 
Crossopterygian fish of the family Holoptychiide. This fish he 
Fia. 162.—Basal bone of dorsal fin, Holoptychius leptopterus (Agassiz). 
(After Woodward. ) 
names Eriptychius americanus. If this identification proves cor- 
rect, it will carry back the appearance of Crossopterygian fishes, 
the earliest of the Teleostome forms, to the beginning of the 
Silurian, these Cafion City shales being the oldest rocks in which 
remains of fishes are known to occur. In the same rocks are 
found plates of Ostracophores and other fragments still 
more doubtful. It is certain that our records in paleontology 
fall far short of disclosing the earliest sharks, as well as 
the earliest remains of Ostracophores, Arthrodires, or even 
Ganoids. | 
Megalichthyide —The Megalichthyide (wrongly called ‘‘ Rhizo- 
dontide’’) have the pectoral fins obtuse, the teeth relatively 
simple, and the scales cycloid, enameled. There are numer- 
ous species in the Carboniferous rocks, largely known from 
fragments or from teeth. Megalichthys, Strepsodus, Rhizo- 
dopsis, Gyroptychius, Tristichopterus, Eusthenopteron, Cricodus, 
and Sauripterus are the genera; Rhizodopsis sauroides from 
the coal-measures of England being the best-known species. 
The Osteolepide differ from the Megalichthyide mainly in 
the presence of enameled rhomboid scales, as in Polypterus and 
