86 Mr. T. Attliey on various Species o/Ctenodns. 



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 f inch long and -^^ 

 inch broad; the inner margin is produced and angulated 

 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 radiate 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 ; tliey 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 than 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, 

 2^ 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, is 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 posterior 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 imbricated, and the grooves are 

 scarcely angulated. 



