630 J. W. DAVIS ON REMAINS OF FOSSIL FISHES 
diameter. Outer lateral margin convex; inner one concave; 
apparently conforming to the contour of the jaw, to which the under 
surface, by its concavity along the longer axis of the tooth, is adapted 
for attachment. Crown thickly enamelled, punctate. Under surface 
of tooth striated or rugose, 
AsTRABODUS EXPANSUts, Davis, sp.n. (Plate XXVI. figs. 11, 11a, 12.) 
Teeth. More or less lingulate in shape ; greatest length 2-5 inches, 
breadth 1°5 inch. At a distance of one sixth the length from the 
anterior extremity the surface is raised, and forms a prominent 
convexity across the tooth at its greatest breadth. From this pro- 
minent part the diameter and thickness of the tooth rapidly 
diminish, terminating posteriorly in a subrotund outline 0-4 inch 
in diameter. The anterior portion of the crown is short, de- 
pressed at an angle of 90° to the anterior margin, which is more 
or less circular in outline. The outer lateral margin is convex, and 
considerably longer than the opposite inner one, which is concave, 
Coronal surface antero-posteriorly concave and transversely convex, 
assuming a saddle-shaped form thickly coated with enamel or 
dentine, and uniformly punctate. Under surface hollow and con- 
cave, apparently for attachment to the surface of the jaw, roughly 
punctured or fibrous in structure. 
These peculiar teeth resemble those of Psammodus, Ag., in the 
widely expanded surface of the crown. Other and more important 
characters indicate some relationship to the less convolute forms 
of the Cochliodont group. The convex upper surface with the 
corresponding concavity beneath, and the greater extent of the outer 
compared with the inner margin, afford considerable evidence that 
the teeth grew or increased in size along the outer edge in a radially 
convolute manner, similar to the growth of the Cochliodonts, so that 
the teeth, in place of being arranged over the surface of the whole 
palate as was probably the case in Psammodus, were restricted to 
the jaws, which they envelopedas ‘in the Cochliodonts. 
The number of teeth in Mr. Horne’s collection is about half a 
dozen. They are allof the same form, but in some of the number 
the long posterior extremity extends towards the right, in others 
towards the left, indicating that they enveloped the opposite rami of 
the jaw. ‘There is no evidence to show that more than one tooth 
was attached to each ramus of the jaw; and though, considering the 
paucity of the material, it might be premature to venture on a 
definite opinion that the fish possessed only two teeth to each jaw, 
such appears to have been the case. 
Genus Crrtonopts, Davis, g. n 
Teeth. Anteriorly prominent, gibbous, rounded towards the extre- 
mity. Surface behind and parallel with the gibbosity much depressed, 
forming a deep hollow extending transversely across the surface ; 
posterior portion of crown more or less triangular in outline, rapidly 
narrowing to a point. The coronal surface uniformly punctate and 
