Salmoperce and Other Transitional Groups 247 
We may, however, regard the Zeoidea on the one hand and 
the Heterosomata on the other as distinct suborders. This is 
Fic. 196.—Amphistium paradoxum Agassiz. Upper Eocene, (Supposed ancestor 
of the flounders). (After Boulenger.) 
certain, that the flounders are descended from spiny-rayed 
forms and that they have no affinities with the codfishes. 
Amphistiide.—The Amplistiide, now extinct, are deep-bodied, 
compressed fishes, with long, continuous dorsal and anal in which 
a few of the anterior rays are simple, slender spines scarcely 
differentiated from the soft rays. The form of body and the 
structure of the fins are essentially as in the flounders, from which 
they differ chiefly by the symmetry of the head, the eyes being 
normally placed. Amphistium paradoxum is described by Agas- 
siz from the upper Eocene. It occurs in Italy and France. 
In its dorsal and anal fins there are about twenty-two rays, 
the first three or four undivided. The teeth are minute or 
absent and there is a high supraoccipital crest. 
The John Dories: Zeide.—The singular family of Zezde, 
or John Dories, agrees with Chetodonts in the single char- 
acter of the fusion of the post-temporal with the skull. The 
species, however, diverge widely in other regards, and their 
ventral fins are essentially those of the Berycoids. In all the 
species there are seven to nine soft rays in the ventral fins, as 
in the Berycoid fishes. Probably the character of the fused 
