84 Mr. T. Atthey on various Species of Ctenodus 



rangement; the anterior ridge, which is wider than the 



others, is reflected and prolonged for some distance beyond 



tlie outer margin ; the tubercles are conical, with obtuse 



points ; those next the external border are coated with 



shining enamel, and are well produced. 



The mandibular tooth differs from the palatal in being 



narrower, and is so convex as to resemble the longitudinal 



section of a cylinder ; the two or three anterior ridges, too, are 



much shorter than the rest, the inner margin sloping rather 



rapidly away in front. 



There are half a dozen of this species in my collection, all 

 of which were obtained at Newsham ; and in the Newcastle 

 Museum there are two others, which were likewise procured 

 from the same locality, and are from the collection of G. B. 

 Forster, Esq. They are all in excellent condition, agree 

 perfectly well in every respect, and can be at once dis- 

 tinguished from C. cristatus by the deep and sharp ridges 

 and by the form of the tubercles, which in G. tuberculatus are 

 always exactly conical (when they are in a fresh state) at the 

 outer margin. When worn, however, they are much flattened 

 at the sides in the direction of the ridges ; and then they are 

 wedge-shaped, and they and the whole of the ridges become 

 granulated. 



3. Ctenodus corrugatus, n. sp. 

 Tooth plate-like, thin, subtriangular, 3 inches long, 2 inches 

 broad ; the surface is slightly convex, and raised into nine 

 stout, somewhat irregular, rounded ridges or wrinkles, 

 the grooves dividing them being wide and rounded ; 

 the ridges die out towards the inner and outer margins, but 

 are enlarged a little as they approach the external border, 

 and are indistinctly and irregularly tuberculated ; the inner 

 margin is nearly straight, the outer slightly convex, the 

 anterior slopes forward from the inner margin, and the 

 posterior is produced and rounded. The whole surface is 

 strongly and irregularly punctured. 



I have seen only one specimen of this fine, large, distinct 

 species : it is a palatal tooth, and is in a very good state. It 

 was obtained from the Collingwood Main Pit, and was pre- 

 sented by George Johnson, Esq., to the Newcastle Museum. 

 It is readily distinguished from its allies by the fewness of the 

 ridges, by their roundness and wide separation, as well as by 

 their greater size and general form. 



4. Ctenodus ohliquus^ n. sp. 

 Tooth depressed, lanceolate, 1^ inch long, f inch broad ; the in- 



