Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 497 
base of the tail; the latter is short, but its lobes are widely expanded to a 
diameter of 4 or 5 inches. The internal anatomy of the fish is well preserved, 
and patches of scales remain, principally on the ventral surface. 
The head has a height of 5 inches, and from the snout to the posterior 
margin of the operculum it is 3 inches. The orbit is large: it is situated in the 
superior portion of the head. The post-orbital region is occupied by large, 
elongated, enamelled opercular plates; their anterior margin is concave, posterior 
one convex; the plates are not sufficiently well preserved to determine their 
number or exact relative position. Below the operculum there is a number of 
branchiostegal rays. The mouth is placed on the inferior part of the head, 
separated by nearly 2 inches from the orbit ; the lower jaws are 0:7 of an inch in 
length, broad behind, but narrowing forwards after the manner of the Pyenodonts ; 
five rows of teeth are spread over the rami of the jaws and the palate. The 
teeth are small, with rounded, flat apex, supported by a contracted peduncle, the 
whole teeth being raised from the jaw one-twentieth of an inch, the height being 
slightly greater than the breadth of the surface. The upper jaw is large and 
massive. The frontal bones are large, and extend with a bold curvature to a 
position above the eye. The surface of the head bones, where exposed, is covered 
with raised tubercles of a round shape. 
The vertebral column is large and massive, and extends with a slight curvature 
from the head to the tail. That it was notochordal, without bony centres, is 
proved by the entire absence of osseous remains. The column consisted of about 
thirty-eight vertebrae, of which twenty-three are caudal. The vertebrae towards 
the occiput are somewhat hidden by a patch of matrix, and, in consequence, 
the number of abdominal vertebrae cannot be given except approximately ; they 
are O’4 inch in height and 0°25 inch broad; near the tail the vertebra are 
somewhat smaller. The terminal eight of the caudal series support the tail ; 
they exhibit a decided flexure towards the superior lobe of the tail; the last 
three radiate from a common centre (Pl. xxu., fig. 1), and expand with a 
spatulate extremity exposed towards the caudal fin-rays, the median portion of 
which they support. The five succeeding vertebrae are much narrower and 
closely impacted; they afford a basis for the attachment of the long rays of the 
upper and lower lobes of the tail. The remaining fifteen of the caudal vertebree 
each support a neural and hemal spine. The spines are strong, and nearly 
or quite straight; they extend backwards in a diagonal direction and support 
a series of interneural and interhzmal bones, to which, in their turn, the fin-rays 
were attached. Each neural spine was spliced with at least two interneurals, and 
the fin-rays correspond in number with those of the latter. The interneural 
spines, varying from 0°9 inch in length, where they support the anterior rays of 
the fin, to 0°3 near the base of the tail, are more or less pointed at each 
extremity ; a ridge extends along the median surface, and from this there extends 
