410 On the Fossil Fishes of the Carboniferous Limestone Series of Great Brita. 
Genus—Diclitudus, Davis. 
Teeth, small. Crown with two subequal prominent cones separated by a deeply 
concave depression of the surface. Base of the crown conforming with the superior 
surface. Root sinuously parallel and co-extensive with the base of the crown. 
Diclitodus scitulus, Davis. 
(Pl. LL, figs. 29, 29a.) 
Teeth, small. Crown consisting of two cones ; transverse diameter ‘3 of an inch, 
height ‘2 of an inch. Cones, equal in size, separated by a circular hollow equal 
in depth to the external lateral margins of the cones and about one-half the entire 
height of the tooth. A ridge extends from each lateral extremity transversely 
across the tooth, having slight indications, when magnified, of tubercles. The apex 
of each cone is obtusely rounded, smooth and enamelled; surface uniformly 
punctate ; the basal margin of the crown is sinuous, conforming to its superior 
outline, it consists of a prominent, slightly recurved ridge, separated by a sulcus 
from the upper surface. Root, equal in depth to the height of the crown ; close, 
fibrous structure, parallel with the sinuosity of the base of the crown and two 
rows of deep regular punctures, with an intermediate ridge ; attenuated below ; 
under-surface similar in outline to the base of the crown. 
Several examples of this peculiar tooth have been found in the Limestones of 
Wensleydale along with some other unique forms. It appears to resemble in 
structure the teeth of Orodus, but its double biconal arrangements separate it from 
any other genus hitherto described. 
Formation and locality ; Carboniferous Limestone, Wensleydale, Yorkshire. 
Ex coll. William Horne, Esq , Leyburn. 
Group.—Cochliodontidz, Owen. 
Cochliodontide—R. Owen, 1867. ‘‘ Geological Magazine,” Vol. IV., p. 59. 
A well defined group of fish-palates, with many characters in common, is 
represented in the Carboniferous series of rocks almost exclusively. The central 
genus of the group is Cochliodus, and branching with various modifications are the 
genera Streblodus, Sandalodus, Deltodus, Psephodus, Deltoptychius, Pzecilodus, 
Xystrodusazd Tomodus. Before proceeding to describe the peculiar characteristics 
of this group, it may be woth while to briefly summarize the opinions, classificatory 
or descriptive: which have already been published. The remarks applied by the 
late Protessor Agassiz to the teeth of Placoid fish in general are especially true of 
this group. After pointing out the imperfection of the actual knowledge of 
cartilaginous fishes, he remarks that surprise should not be felt at the little 
progress made in the study of the fossils pertaining to this group of animals. The 
difficuities attending the determination of the teeth of sharks and rays, which are 
