Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 627 
NOTES ADDED IN PRESS. 
Petalopteryx dorsalis, Davis. 
(Blix) fig./4.,) 
A small fish, elongated in form; greatest height behind the pectoral fins and 
gradually diminishing towards the tail. The vertebral column extends to the 
upper lobe of the tail. The length of the fish is 2°7 inches: of this the head 
occupies 0°35 inch; the height of the posterior part of the head is equal to the 
length ; the snout is obtuse and rounded. The orbit lies above the median line, 
large and well defined; the supra-orbital area small. The anterior parts of the 
jaws are displaced; the operculum high and rounded posteriorly immediately 
beneath the mandible. The anterior termination of the left mandible is exposed, 
and is full of minute, closely-set, erect teeth, sharply pointed and elongated. 
Branchiostegal rays are present; seven are visible, and are comparatively thick 
and strong. 
The vertebral column is osseous and well defined, the thick and well-preserved 
coating of scales prevents its exact description ; its direction can be distinguished, 
and the extension of its caudal extremity to the upper lobe of the tail is very 
marked. 
The dorsal fin extends apparently from the occipital part of the head to the 
base of the tail. The fin-rays are hidden by the matrix, 0°2 inch at the anterior 
extremity of the fin, the remaining part is exposed ; the rays are widely separated, 
strong, and straight, diminishing in size as the posterior end of the fin is 
approached. 
The anal fin cannot be distinguished. The caudal has a few short rays on the 
upper surface of the upper lobe, and from the under there extends twelve strong 
rays; they are articulated; but so far as this specimen exhibits them they are 
undivided. 
The pectoral fins are situated on the side of the body, supported by a strong 
pectoral arch, to which they are attached. The number of rays cannot be 
distinguished; the anterior rays are the strongest, diminishing in size backwards. 
The ventral fins are 0-8 inch behind the pectorals; they were small, and in this 
specimen are not well preserved. 
