On the Fossil Hishes of the Carboniferous Limestone Series of Great Britain. 437 
The teeth of the upper jaw have#similarly developed from the outer margin of 
the tooth : a transverse section of ajtooth, (Plate LIV., Figures 3a, 4a), represents 
the incurved lateral margin on the outside of the dextral tooth. The growth 
in this instance very nearly approaches that of the tooth of Deltodus sublevis, and 
serves to show the close connexion that exists between the genera Cochliodus, 
Sireblodus, and Deltodus. The suggestion is also forcibly impressed that the upper 
teeth of the genera Cochliodus and, Streblodus were probably somewhat similar 
in form to Sandalodus and Deltodus, and though they have not yet been determined, 
it is not improbable that they may be found amongst some of the teeth now con- 
sidered either as separate genera or classified with some other one. 
Sandalodus morrisu, Davis. 
(Pl. LIV., figs. 1-6.) 
Deltodus sp. ?—Morris and Roberts, 1862. “ Quart. Journ. Geol. Soc.,” Vol. XVIIL., p. 105. pl. 3, 
now ela. 
Teeth of lower jaw, large and massive, 4’5 inches in length, and 1°75 in breadth 
near the centre. Crown longitudinally convex, transversely deeply convex, smooth, 
polished, uniformly and finely punctate, surface evenly rounded, with the exception 
of one or two flattened areas, apparently worn by attrition. Lateral margins 
slightly rounded, extremity obtusely pointed. Base “4 inch thick near the end, 
thinner in the centre of the tooth, partakes generally of the form of the crown, but 
is considerably constricted in extent. 
Teeth of upper jaw, large in size, thick and strong, triangularly elongated, 
posteriorly convoluted, length 40 inches, breadth anteriorly 1°8 inch. Crown in 
longitudinal section, the surface is deeply convex, the external lateral margin 
formed by a prominent ridge, which extends from the anterior apex towards the 
posterior margin, becoming much expanded and proportionately depressed. The 
internal lateral surface is more or less expanded and concave. The surface of the 
crown is uniformly and minutely punctate. Where the surface has not been 
abrated each minute orifice is surrounded by a raised ring of black enamel, the 
enamel being continuous from one pore to another, and covering the interme- 
diate space. Posterior margin rounded or circular, considerably worn by attrition ; 
the median lateral margin slightly convex, the opposite margin straight, angular, 
and convoluted. A transverse fracture shows the tooth to be at least 4 of an 
inch thick. The base is thick, strong, and fibrous in structure, full of ramifying 
dentigerous canals in connexion with the punctate orifices of the surface enamel. 
The base projects some distance beyond the crown along the posterior surface, and 
also for a distance of an inch and a half along the inside lateral margin ; in other 
respects it conforms generally to the surface of the crown. ‘The anterior portion 
of the tooth is thinnest, and its thickness increases backwards in the same ratio 
that the tooth increases in size. From the rough, porous, incomplete appearance 
