310 Mr. T. Attlicv on ('tcniidus ()l)rK|im>. 



Ctenodus, corresponding exactly a« it did in conformation to 

 the arfinilar hono of the recent Crrattx^iis. 



Last year (1874) I was fortunate enougli to fnidj also at 

 Newsham, two fine specimens of Ctoiodiis dhUijuns with this 

 very articular bone in situ ; and one of these is figured on 

 Plate XIX. figs. 1 and 2. 



The bones differ in size, being from | of an inch to 

 4 inches in length. The inner side of the mandible is 

 formed by the ramus or body of the jaw surmounted by the 

 teeth ; and these at their u))per margins are turned outwards 

 and tlattened, and project towards tiie nj)per border of the 

 articular or external piece. The narrow elongated space left 

 between the two bones of the fossil at this part would neces- 

 vsarily in the fresh state be filled with connective cartilage and 

 ligament, just as the convsponding space is in the recent 

 r V ratodu s Fo rsteri. 



The articular bone of Ctenodus is of about the same length 

 as the inner plate or ramus which bears the teeth, slightly 

 convex on the outer surface, and marked by five or six aper- 

 tures for vessels ; it is pointed upwards in front like the prow 

 of a boat. Its posterior border presents two scallops, the 

 upper somewhat larger than the lower, which extends to the 

 posteriorly projecting i)oint of tlie lower border, which is 

 convex ; the upper scallop ends at a rounded })rojeetion, which 

 separates it from the upper border. This border presents two 

 shallow concavities, the anterior occupying the greater part of 

 the border ; the posterior has a projection on its inner side, 

 somewhat in the form of a bracket, for tlie su])]wrt of the 

 teeth of the inner ])late or ramus. 



On a thin slab of shale from Newsham in my possession, 

 and which measures o by 'd\ inches, are seen imbedded one 

 rib, several bones of the head, fragments of scales, and what 

 I take to be right and left vomerine teeth of Ctenodus^ one of 

 which is figured on Plate XIX. fig. 4. The teeth are -^ of 

 an inch broad, and thick at the base — their outer surfaces 

 being slightly convex and their inner slightly concave, the 

 two surfaces converging from the base to the thin, convex, 

 serrated or toothed margin, which is -p%-of an inch long. The 

 microscopic structure of these teeth corresponds exactly with 

 that of the maxillary te«th of Ctenodus. 



I possess about a dozen other specimens believed to be 

 vomerine teeth of Ctenodus^ in elr)se j^roximity on the same 

 slabs to the V»ones of tlie head and teeth of Ctenodus ; some of 

 these are a little Larger, others a little smaller, tlian the two 

 above described. 



