336 WOODWARD : fossil fishes of the upper lias of WHITBY. 
and all other sufficiently well-known forms of the genus, however, 
the Whitby fish may be readily separated by the following specific 
diagnosis — 
A robust, round-bodied species, attaining a length of somewhat 
more than half a metre. Length of head, with opercular apparatus, 
about equalling the maximum depth of the trunk, and contained 
four times in the total length of the fish. The cranial roof-bones 
and cheek-plates more or less sparsely tuberculated and rugose, but 
the maxilla and opercular apparatus smooth. Supratemporal plates 
forming a single symmetrical pair; parietals relatively large, extend- 
ing at least over one-third of the total length of the cranial roof, 
both these and the frontals meeting each other in a wavy, sharply- 
angulated suture ; the length of each frontal about two-and-a-half 
times its maximum width ; suborbital cheek-plates four or five in 
number, the one directly behind the eye relatively large and 
deepened : antorbitals three in number, deeper than broad. 
Marginal teeth slender styliform, about eight in the premaxilla, and 
thirteen in the dentary, these of nearly equal size, those of the 
maxilla slightly smaller. Operculum two-thirds as broad as deep, 
suboperculum twice as broad as deep, and the narrow preoperculum 
covered by the suborbitals at its upper end. Fin-fulcra moderately 
developed, slender ; pelvic fins arising nearer to the anal than to the 
pectorals ; anal fin midway between the pelvic pair and the caudal 
fin. Scales smooth ; the principal flank-scales slightly deeper than 
broad, with a few coarse serrations on the lower half of the hinder 
margin ; dorsal ridge-scales relatively small and inconspicuous ; 
enlarged median anal scale with digitate pectinations at its tapering 
hinder end. 
Explanation of Plates. 
Plate XLYI. 
Fig. Page. 
1. Lepidotus semiserratus, Agassiz; roof of skull, fr., frontal; 
L, groove for slime-canal; pa., parietal; s.t., supra- 
temporal; s^/.j squamosal. [35556.] ... ... ... 326 
