426 CLASSIFICATION OF DEVONIAN FISHES 
in form and sculpture, widely different from those of the latter 
genus. 
That Platygnathus (Agassiz), if we restrict the name to the fish 
whose caudal extremity is figured by Agassiz (“ Vieux Gres Rouge,” 
Tab. 25), is very closely allied to Holoptychius cannot be doubted ; 
indeed, the only serious question regarding it, in the absence of 
further materials for its reconstruction, seems to be, whether it 
should really form a separate genus; so that I may pass on to 
another generic type, Glypéolepis (Agassiz). 
This genus is briefly mentioned in the “ Recherches sur les Poissons 
Fossiles,” ii. p. 179, but Agassiz first described and figured species of 
TAAL 
NONARUNNSN 
NY » NA) 
aN 
4 ‘ 
PA 
i 
Fig. 5. Restoration of Holodtychius. 
it in the “ Monographie des Poissons du Vieux Grés Rouge,” p. 62, 
where Glypéolepis heads the family of the “ Célacanthes,” and is said 
to comprise fishes of moderate size, with pyriform bodies, and with 
heads which are small, short, flattened, and have an almost semi- 
circular contour. The rami of the mandible are stated to be beset 
throughout their length with a single series of small, equal, conical 
teeth, which seem to approach those of Dendrodus and Holopty- 
chius in structure, and to have a dendritic pulp cavity surrounded 
by folded dentinal walls. Glyptolepis microlepidotus, however, 
is said (p. 65) to possess large teeth alternating with small ones in 
the lower jaw. The upper jaw projected beyond the lower a little, 
and had similar teeth. The throat was provided, as “in all ancient 
“Ccelacanths and in Polypterus, with two mobile triangular plates, 
“which replace the branchiostegal rays.” 
The scales were delicate, rounded, and so much imbricated that 
the anterior one sometimes covered more than half of its successor, 
Their upper faces were entirely smooth, and covered with a delicate 
layer of enamel, which, apart from some concentric lines of growth, 
