FROM THE-YOREDALE SERIES, 633 
there is a second and similar convex protrusion of the surface, the 
posterior portion of which extends a considerable distance back- 
wards, the lateral margins gradually converging to half its greatest 
breadth and terminating in a rounded extremity. The surface is 
covered with small pustulations: base not observed. 
The teeth comprised in the above description appear to offer some 
indication that they are allied to some extent with the Cochliodont 
group of fishes. As with the genus Cochliodus, the concave margin 
is shorter than the convex one, and the two prominent portions of 
the coronal surface are narrow and somewhat pointed at first, and 
expand with the growth of the tooth. These characters, combined 
with the general appearance of the tooth, point to a surface more 
or less convolute and expanding radially with the increase in size. 
DreLacopts BuLBoIDES, Davis, sp.n. (Plate XXVII. fig. 20.) 
Teeth. Possessing the generic peculiarities already indicated ; 
length 0-7 inch, breadth 0-4 inch. The anterior portion of the 
tooth is characterized by a doubly convex projection of the surface 
of the crown, divided by a deep transverse groove from the second 
projecticn. The surface of the toothis prolonged backwards for a 
length equal to half that of the tooth; the sides converge to 0-2 inch 
in diameter, the posterior extremity being obtusely rounded. The 
margin of the anterior portion of the tooth is deep and slightly 
convex ; the inner lateral margin sinuously concave, with more or 
less pointed projections from the border, corresponding to the two 
‘prominences of the crown; the outer margin is convex, with 
rounded projections of the surface similar to the inner ones. The 
surface of the crown is generally convex, expanding with growth. 
It is coated with dentine, which is uniformly and minutely punctate ; 
root or base not exposed. 
The figure shows a mass of matter attached, which may be a 
portion of the bony or cartilaginous jaw. 7 
- Genus Mrearrcutiys, Agassiz. 
Mecaticutuys Hissertr, Ag. (Plate XXVI. fig. 8.) 
A jaw and a few separate teeth and scales of this fish have been 
found. The jaw is rather less than an inch in length, and 0°3 inch 
in depth at the posterior end, becoming narrower towards the 
anterior symphysis. It is covered with glistening black enamel; 
the surface of the latter being covered with pittings similar to those 
of the Megalchthys abundant in the Coal-measures. Along the 
upper or alveolar surface a row of minute teeth may be distin- 
guished. The specimen is represented, natural size, by fig. 7. 
Several other fossils, apparently belonging to fishes, also occur, 
but in too imperfect a condition to allow their precise nature to be 
made out. One is a small, circular, convex plate covered with 
