334 WOODWARD : fossil fishes of the upper lias of WHITBY. 
behind and below the opercular apparatus. Its flattened external 
face is rather broad, apparently quite smooth and destitute of 
enamel. It is bordered posteriorly by the usual enamelled post- 
clavicular plates {jj. cJ.), of which the two uppermost are well dis- 
played above the hardened clay containing fragments of the pectoral 
fin. Their hinder margin does not bear any serrations. The 
principal scales of the flank in the abdominal region are deeper than 
broad ; while those both dorsally and ventrally are observed to be 
smaller and more nearly equilateral, or even broader than deep. 
Many of the former exhibit conspicuous serrations on the lower half 
of their hinder margin, but the latter are entirely smooth. On the 
tail the scales gradually become much smaller, and nearly all of 
them are broader than deep, with the postero-inferior angle — 
sometimes also the antero-superior angle — produced into a slender 
point. All are quite smooth, without serrations ; while some 
towards the ventral border and at the base of the caudal fin (c.) are 
very irregular in shape. At the base of the anal fin (a.) there are 
also remains of the enlarged anal scales. The course of the lateral 
line on the flank is indicated by a series of simple perforations, 
sometimes with a partly raised rim, extending along a row of scales 
from a point just above the upper postclavicle to the middle of the 
caudal pedicle. No scale of this row is pierced by more than one 
opening, and for the most part only the alternate scales appear to 
be marked. 
The two fine examples just described show very little of the 
overlapped anterior margin and the inner face of the scales. These 
features are better observed in the scattered squamation of Brit. 
Mus., No. P. 5223, from which the originals of pi. xlvii., figs. 2-4, are 
taken. Fig. 2 represents an abdominal flank-scale, imperfect behind 
but beautifully exhibiting the anterior overlapped margin, which is 
extended at its antero-superior angle into a long prominence, and 
is also slightly produced forwards antero-inferiorly. Fig. 3 shows 
the inner aspect of a scale, probably from the postero-dorsal part of 
the abdominal region. The anterior overlapped border exhibits the 
characteristic prominences noticed in the previous specimen; a broad 
rounded ridge or thickening extends vertically across the middle of 
