568 Davis 
On the Fossil Fishes of the Chalk of Mount Lebanon. 
in front of the dorsal fin is 1:0 inch; at the peduncle of the tail it has diminished 
to 0°4 of an inch. The body is short and proportionately deep and strong. 
The pectoral fins are peculiar from their length and evident capability for 
expansion. 
The head is nearly as high at the posterior part as it is long, and rapidly 
diminishes forwards, assuming a triangular form; as already observed, it has not 
been well preserved. The gape is very wide; the mandible 0-7 of an inch in 
length, and the maxillary bones about the same; teeth cannot be distin- 
guished. he orbit is about 0-4 of an inch behind the snout. The opercular 
bones appear to have been large, and are coated with enamel. There are ten 
branchiostegal rays on the side exposed, the longest 0°3 of an inch in length, 
fine, and gracefully curved backwards. 
The spinal column is composed of thirty-four vertebra, of which the caudal 
region of the fish comprises sixteen; they are not preserved, but their form and 
number is sufficiently well indicated by the impression they have left; the 
vertebrae were small, and equal in length to their height. The ribs are long 
and fine. The neural spines connected with the vertebrae by neurapophyses are 
long, and curve considerably backwards. Attached to the hamal spines in the 
caudal region are interhemal spines which support the anal fin. The interneural 
spines are short, broad, and strong. 
The dorsal fin is large; the anterior rays are 0°75 of an inch in length; the 
succeeding posterior rays diminish gradually in length to 0°15 of an inch. The 
rays are fourteen in number, and the distal extremities of the rays are sub- 
divided, but not articulated. The base of the fin extends 0°6 of an inch; it is 
0:7 of an inch behind the head, and is separated from the caudal fin by 1:0 
inch. The anal fin is composed of fourteen rays; its base extends 0°6 of an 
inch, the posterior rays being separated from the tail by 0°2 of an inch. The 
caudal fin is 1:0 inch in length, deeply forked, and composed of twenty-two rays, 
eleven in each lobe; the rays are bifurcated and articulated; the external rays 
of each lobe are supported by rudimentary rays. The last vertebra of the spinal 
column is expanded to a rounded, flattened hypural plate, which gives support to 
the caudal rays. . 
The paired fins are large and important. The pectorals are fixed immediately 
behind the gill covers on the abdominal surface of the body; they are supported 
by thirteen or fourteen rays, which repeatedly dichotomize, but are not jointed, 
producing a filamentous arrangement at the margin. These fins are more than 
1:0 inch in length, and were evidently capable of great expansion. The ventral 
fins are similar to, but smaller than, the pectorals; each contains eight rays, and is 
supported by a large triangular internal bone; its position is opposite to the 
posterior rays of the dorsal fin. The body is covered with elongated scales, 
somewhat dense in structure, with smooth surfaces, 
