594. Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 
diameter thus equalling two-fifths of the greatest. The specimen is in good 
preservation. ‘The anatomy of the head and body, and the position and con- 
stitution of the fins are displayed to advantage. The body is highest 0°6 of an 
in front of the dorsal fin, and from thence it gradually narrows to the peduncle 
of the tail, which is 0°5 of an inch anteriorly; it also converges to the snout. 
The fins, except the pectorals, are all situated far backwards; the caudal deeply 
cleft, the extremities of the two lobes being 2:5 inches apart. 
The height of the head posteriorly is 0°7 of an inch, and its length is the 
same; it is subtriangular in outline, the snout bluntly rounded. The orbit is 
placed midway between the occiput and the snout, and very high; the bones of 
the infra-orbital ring are well defined; the parasphenoid, which crosses its lower 
part, is strong, and connected with it anteriorly, the vomer is exhibited. The 
maxillary is 0-8 of an inch in length; the pre-maxillary is short and strong; it 
is slightly displaced in this specimen. The mandible extends 1:2 inch; it is a 
narrow bone, slightly expanded posteriorly, and forms the lower margin of the 
head; the branchial apparatus is not exhibited. Attached to the mandible is a 
bone diverging upwards in a triangular form, which is probably the quadrate or 
hypotympanic bone; attached to the posterior limb of this a long bone (hyo- 
mandibular) connects it with the cranium; other bones, not well defined, occupy 
the tympanic area. The post-orbital bones are elongated and narrow; the 
pre-operculum, as well as the inter-operculum, have been to a large extent removed 
with the opposite matrix; the operculum is twice as high as broad, convex 
posteriorly, but concave in front; the sub-operculum is comparatively small and 
subtriangular in outline; the inter-orbital space is narrow, the frontal bones well 
developed and strong; midway between the orbit and the snout there is a tooth 
0-15 of an inch in length, conical, and sharply-pointed ; it is dissociated from the 
jaws, but has the appearance of having formerly been connected with them; there 
is also evidence of two or three small teeth attached to the lower jaw. 
The spinal column consists of forty-nine vertebrae, of which fifteen are 
included in the caudal region. The anterior portion of the column has been 
somewhat displaced, as indicated in the figure. ‘The vertebre are broad as long, 
the median portion deeply contracted. The neural and hemal spines in the 
caudal region are short and fine; the interhzmal spines supporting the anal fin 
form almost a right angle with them; the interneural spines supporting the dorsal 
fin are laid more nearly parallel. The ribs are numerous, long, and fairly strong; 
they extend to the ventral surface of the abdomen; the stylets or epipleural spines 
extend diagonally from the ribs. The neural apophyses and spines in the 
abdominal region are also numerous and strong, especially near the head the 
neural spines are very thick and strong. 
The dorsal fin is very posteriorly placed; its anterior ray is 3°3 inches behind 
the snout and 2 inches before the caudal fin; it is 0-8 of an inch in length, and 
