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 
the 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 bein 
narrower, and is so convex as to resemble the longitudina 
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’ ~ ridges 
and by the form of the tubercles, which in C. 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 obliquus, n. sp. 
Tooth depressed, lanceolate, 14 inch long, ? inch broad ; the in- 
