WOODWARD : FOSSIL FISHES OF THE UPPER LIAS OF WHITBY, 31 
arched and that certain head-bones, notably those of the cranial roof, 
were ornamented with closely arranged, though coarse, rugae. A 
second specimen (Brit. Mus., No. P. 1058a) exhibits the head a little 
more satisfactorily (pi. iv., fig. 1). The cranial roof is exposed, 
crushed and fractured beyond recognition behind and in front, but 
displaying the large frontal bones (fr.), united in a wavy median suture, 
and a smaller plate on the right side, which may be either pre- 
frontal or nasal {na). These bones are beautifully ornamented with 
closely vermiculating rug?e, not readily represented in a figure. The 
cheek-plates and jaws are too much crushed and confused for des- 
cription ; so also are the opercular bones, except the interoperculum 
and the lower end of the preoperculum. The former (t. op.) is 
triangular, somewhat deeper than broad ; the latter {p. op.) is much 
expanded, and a fracture at its antero-inferior angle shows four of 
the radiating passages of the slime-canal filled with spar. The 
outer face of both these elements is nearly smooth and flat, but 
with traces of flattened tubercles in the lower portion. Two frag- 
ments of maxilla {mx.) indicate that this bone was externally 
ornamented behind with tubercles and short ruga?, anteriorly with 
longitudinal striae. Behind the opercular apparatus the curved 
lower end of the robust clavicle (c/.) can be seen, and there is a 
pectoral fin consisting of robust, distally bifurcating rays. The scales 
are very imperfect, but those of the middle of the flank are obviously 
deeper than broad. 
Delicate ring-vertebrae are observed in the abdominal region of 
one specimen (pi. iv., fig. 2), but nothing further is known of the 
endoskeleton of the trunk. 
The left pectoral fin in the specimen which displays the ring- 
vertebrae seems to be complete except at the distal end, and exhibits 
eighteen stout rays. The pelvic fin, well preserved in No. P. 4406 
(pi. iv., fig. 3), has only eight similar rays, all closely divided and 
articulated in the distal portion. The proportions of the caudal fin, 
as indicated in the same specimen, are shown in pi. iv., fig. 4. The 
articulations are distant in the proximal half of the rays of the 
lower lobe, and four of the small fulcra are preserved on the anterior 
margin of this lobe. 
