CATALOG OF THE FOSSIL FISHES IN THE CARNEGIE MUSEUM. 



409 



very small specimen in counterpart (4456,4456a), which is perhaps to be regarded 

 as indicating a dwarf variety. The subjoined restoration of this species (Fig. 3) is 

 copied from A. Smith Woodward. 



Genus Gyrodus Agassiz. 



"Trunk deeply fusiform or discoidal, with a slender abbreviated caudal 

 pedicle. Head and opercular bones ornamented with tubercles; cheek and gular 

 region covered with small, imbricating cycloidal scales; teeth more or less rugose 

 and mammillated, those of the vomer in five, and those of the splenial in four 

 regular series. Neural and hsemal arches of axial skeleton of trunk not expanding 

 sufficiently to encircle the notochord. Fin-rays robust, closely arranged, articu- 

 lated, and divided distally. Pelvic fins present; dorsal and anal fins low and 

 fringe-like, except in front where they rise to an elevated point, these two fins 

 arising at about the same point and not extending in advance of the hinder half 



Fig. 4. Gyrodus hexagonus (Blainville). (After E. Hennig in "Palseontographica," Vol. LIII, 1906i 



PI. XI, fig. 2.) 



of the trunk; caudal fin deeply forked, with slender lobes. Scales tuberculated or 

 rugose, covering the whole of the trunk" (A. S. Woodward, I. c, Pt. Ill, p. 233). 



