WOODWARD : FOSSIL FISHES OF THE UPPER LTAS OF WHITBY. 161 
proximal end. Behind the head there are scattered remains of the 
very delicate arches of the vertebral axis. They are filled with spar 
in the fossil, and must thus have been only imperfectly calcified. 
The nodule in the Egerton Collection (No. P. 2039) displays the 
fragmentary remains of the right side of the head and opercular 
apparatus from within. It shows that the suboperculum is much 
broader than deep, and is succeeded below by a long series oi branch- 
iostegal rays which extend forwards to the place that would be occupied 
by the gular plate. These cannot be counted easily, but are more 
than twenty in number. 
No less imperfect specimens of this fish are known from Whitby, 
and it is thus necessary to depend upon those from Ilminster and 
Wiirtemberg for a diagnosis of the species. This may be attempted as 
follows : — 
A species attaining a length of not less than one metre. Head 
with opercular apparatus occupying one-quarter of the total length of 
the fish ; head very short and stout, its length equalling about two- 
and-a-half times the width of the operculum. Cranial roof-bones and 
cheek-plates ornamented with fine delicate tubercles, usually arranged 
along the lines of growth ; teeth slender and incurved at the point, 
round in section, smooth and only exhibiting a few vertical folds at 
the base. Operculum trapezoidal in form and the upper border 
shortest, its maximum width about equal to its depth, and the outer 
face marked only bylines of growth; preoperculum similarly marked; 
branchiostegal rays somewhat less than forty in number. Dorsal and 
anal fins about equally extended, with not less than thirty rays, the 
latter arising just in advance of a point oppos'te the hinder end of the 
former. Scales smooth, those of the "lateral line" on the caudal 
region somewhat enlarged. 
Pachycormus curtus, Agassiz. 
Plate XXL, fig. 1. 
1832. Urceus gracilis, L. Agassiz, Xeues Jahrb., p. 142. 
1833-44. Pachycormus gracilis, L. Agassiz, Poiss. Foss., vol. ii., 
pt. i., p. 12 ; pt. ii., p. 114 (undefined). 
1814. Pachycormus curtus, L. Agassiz, ibid., pt. ii., p. 112, pi. lix 
