86 Mr. T. Atthey on various Species of Ctenodus. 
hinge-line is long, and has a slight projection in the centre ; 
the surface is strongly punctured and granulated. 
5. Ctenodus elegans, n. sp. 
Tooth depressed, triangular, upwards of $ inch long and 55 
inch broad; the inner margin is produced and angulate 
in the centre, whence it slopes in front and behind to- 
wards the outer margin, which is regularly but slightly 
arched; the surface is provided with eight strongly denti- 
culated ridges, which Aaniats from the inner marginal angle, 
where they are very minute, to the outer border; the ante- 
rior ridge is a little produced at the outer margin beyond 
the rest; there are six or seven denticles or tubercles on 
each ridge; they are much compressed at the sides, are 
sharp-pointed and lancet-like with the inner limb a little 
shouldered, where there is occasionally a minute toothlet ; 
the denticle and ridges are coated with enamel, and shine 
very brilliantly. : 
There are sixteen specimens of this minute species in my 
collection ; they were obtained at Newsham and Cramlington. 
The mandibular tooth is very similar to the upper one, but 
is a little narrower ; the latter is somewhat more that half the 
length of the maxillary bone, the posterior extremity of which 
is not much enlarged, and is diagonally truncated. 
This is the tooth before alluded to as having been found in 
connexion with the head of the entire fish, of which a general 
description has already been given. It is therefore unneces- 
sary to say more respecting it on the present occasion. 
6. Ctenodus imbricatus, n. sp. 
Tooth depressed, very thick, hollowed or slightly concave, 
21 inches long and upwards of an inch broad, with the 
inner margin well and regularly arched, the anterior slope 
being much longer than the posterior; the outer margin is 
nearly straight, but, on account of the projection of the 
surface-ridges, 1s coarsely denticulated ; there are six of these 
ridges or plaits; they enlarge rapidly towards the outer 
margin; they are strong, smooth, and somewhat distant 
from each other, and, though mostly inclined forwards, are 
laid over towards the postérior end, having an imbricated 
appearance; the grooves dividing the ridges are angulated ; 
the surface is minutely granulated, and the edges are ena- 
melled. The mandibular tooth is very narrow and fusi- 
form; the ridges are not umbricated, and the grooves are 
scarcely angulated. 
