WOODWARD : FOSSIL FISHES OF THE UPPER LIAS OF WHITBY. 331 
suboperculum, however, still remain almost destitute of ornament, 
only very few tubercles being observable on these plates. Remains 
of the suborbital cheek-plates on the left side seem to indicate that 
the series consists of five elements. Uppermost, there is the small 
trapezoidal plate already noticed in No. 35,556 ; next follows the 
deep plate just described in No. P. 52 13 (pi. xlvi., fig 2) ; immediately 
below this are two plates, the upper one as deep as broad, the lower 
twice as broad as deep, which seem to correspond with the single 
plate shown just below the fracture in No. P.3528a (pi. xlvii., fig. 1); 
and the series is completed by the large trapezoidal element, which 
is also well displayed in the latter specimen. 
The head of another small fish in the British Museum 
(No. P. 7409) has comparatively smooth cranial and facial bones like 
the first specimen already described. It is of special interest as 
displaying the maxilla and posterior suborbital plates. The maxilla 
evidently tapers in front, and gradually deepens behind, until it 
terminates suddenly in a truncated posterior end (pi. xlvi., fig. 3, mx.). 
The outer face of this element is quite smooth, and the anterior 
half of its lower border exhibits remains of slender styliform teeth. 
Above the hinder half of the bone there is a relatively large supra- 
maxilla (s.mx.), which is also smooth and delicate, and tapers to a 
point at each end. In the suborbital series the two upper plates 
seem to be fused together into a very deep bone ; and there are onl} 
two plates beneath it, as in No. P.3528rt. Below the interoperculum 
there are distinct indications of three or four branchiostegal rays. 
The scales of the trunk are much displaced, and some of those 
towards the ventral border display not only the normal small peg- 
and-socket articulation, but also an extremely produced antero- 
superior angle. 
The teeth of the dentary bone are very imperfectly shown in 
the specimens just described, but the mandible of one imperfect fish 
in the British Museum (No. P. 6 394) appears to exhibit the complete 
series. The teeth are styliform, with a short enamelled crown, like 
those of the maxilla, though somewhat larger ; they are uniform in 
size, and regularly spaced, and seem to have been thirteen in number 
on each side. The dental series of the premaxilla, as shown by 
