366 Messrs. Hancock & Atthey on Reptile- and Fish-Remains 
the same size and character, and are equal in number to those 
of the mandible. The largest teeth are nearly one-sixth of an 
inch in length ; they are much wider than they are thick from 
back to front. 3 
On making a longitudinal section of the teeth in the direc- 
tion of the jaw, the structure is found to be very peculiar. 
The jaw itself is composed of very dense bone on the surface, 
in which the Haversian canals are well defined, and the ra- 
diating cells are very numerous and minute; they are elon- 
gated-fusiform, with the canaliculi (when observable) sufficiently 
abundant and arranged for the most part at right angles to 
the long axis of the cells. In the superficial sad denser por- 
tions of the tissue the cells and tubules are the most minute ; 
in the deeper portions they are larger and less regular in form, 
and the bone becomes riddled with medullary cavities, until at 
length it is entirely reduced to a sort of cellular structure. 
This curious cellular tissue is continued into the teeth, and 
forms their central mass, there being apparently no distinct 
pulp-cavity, or, if any, it is confined to the base. This tissue 
becomes less open as it approaches, and gradually forms a 
dense layer at, the surface of the teeth, in which layer the 
Haversian canals are as distinct as they are in the bone of the 
ramus, and the cells, diminished in size, assume.their regular 
elongated form, and at the extreme margin they disappear. 
This peripheral layer, which represents the dentinal wall of 
ordinary teeth, is found to be continuous from tooth to tooth ; 
it differs, however, in no respect from the dense external sur- 
face of the ramus. Indeed it is quite evident that the. bone 
of the jaw is continued into and forms the teeth; they may 
therefore be looked upon as processes of the jaw. We have 
failed to detect the least trace of enamel on the surface of the 
teeth. : 
A considerable portion of one of the pectoral spines lies near 
to the crushed head of this species, in which the jaws are dis- 
tinctly displayed with the teeth interlocked. ‘T’he spine has 
lost its distal extremity; the fragment, however, is flattened 
towards this end; at the basal extremity it is thickened, and 
assumes a triangular form; a groove extends along the ante- 
rior margin. Detached spines have also occurred, agreeing 
exactly with Sir P. Egerton’s description of the pectoral spine 
of this species. 
The scales are minute rhombs, with the upper surface 
smooth and slightly convex. Some appear to be minutely 
and irregularly granulated. Perfectly similar scales clothe 
the heterocercal tail which was procured at Newsham, and 
which we believe to belong to this fish. It is about three- 
