436 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
Genus.——-Sandalodus, N. & W. 
Sandalodus—Newberry & Worthen, 1866. ‘Geol. Sury. Ilinois,” Vol. Il, fo WOZ, 
“Teeth of medium or large size, thick and strong, sub-triangular or club- 
shaped in outline, with one and sometimes two pointed extremities ; generally 
somewhat twisted, slightly arched longitudinally, strongly so transversely ; 
enamelled surface finely and uniformly punctate; base deeply concave both ways, 
curves following those of the surface of the crown ; towards the narrower end in 
some species, one or two obtuse ridges running obliquely over the tooth as in 
Cochliodus.”—N. & W. 
The above is the description of the teeth of the lower jaw ; the following of those 
of the upper one :—Large, thick, massive, triangular in outline, anterior extremity 
pointed and convoluted inwards ; surface more or less concave, expanded posteriorly 
and terminating with a broadly rounded posterior margin. External margin pro- 
minent, angular, and inrolled. | Enamelled surface punctate. Base generally 
similar in form to the crown. A considerable number of specimens of this genus 
have been collected at Oreton, in Salop, and from the Black Rock near Bristol. 
The teeth from both localities are similar, and consist of the two forms 
described above, and though they have not been found associated together in a 
natural position, the fact that teeth of so large a size and identical texture are 
found in two localities similarly associated and other minor considerations, renders it 
almost certain that they are from the upper and lower jaws respectively of the same 
species. The specimens figured, though they may not be from the jaws of the same 
fish, fit each other with tolerable accuracy, the concave surface of the upper jaw 
corresponding to the convex one of the lower. 
The teeth of the upper jaw bear more than a passing resemblance to those of 
Deltodus, and indicate a very close relationship between the two genera. The 
teeth of the lower jaw are more like those of the posterior tooth of Streblodus 
than Cochliodus, as stated by Messrs. Newbury and Worthen. The species now 
under consideration are devoid of the slightest indication of ‘ obtuse ridges running 
obliquely over the tooth,” they are quite plain and smooth. 
The methud by which the teeth of this genus have grown 1s very well shown in 
the specimens figured. It does not appear probable that there was more than one 
tooth to each ramus of the jaw. Those of the lower jaw are incurved, and to some 
extent have enveloped the outer anterior margin of the jaw ; from this surface the 
teeth expand inwards, and are largely developed backwards. The successive in- 
creases in the size of the tooth are occasionally indicated, as on the tooth represented 
by Figure 1, Plate LIV. This is exactly the method by which the teeth of the 
genera Streblodus and Cochliodus increased in size, but whereas the dentition of 
those genera is divided into two or three teeth with prominent transverse ridges ; 
in the present one there is only one undivided tooth without ridges. 
