Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 609 
length, exclusive of the tail, is 4 inches; of this 1:8 inch is included in the 
length of the body from the base of the caudal fin to the occiput; the head 
and the beak-like snout is 2°2 inches. The greatest height is immediately before 
the dorsal fin, where it is 0°85 of an inch. From this point the height diminishes 
posteriorly ; the peduncle of the tail is 0°35 of an inch; anteriorly the height 
remains nearly the same to the occipital region, which is 0-8 inch; the head is 
triangular, the jaws being continued almost straight to the end, and when closed, 
0-2 of an inch across. The fins are well preserved; a distance of 0°8 of an inch 
separates the anterior ray of the dorsal from the head, and from the first ray of 
the dorsal to the base of the caudal is 1:1 inch. The pectorals are 0-8 of an 
inch in advance of the ventrals, which are immediately under the anterior rays 
of the dorsal. The anal fin is 0:7 of an inch behind the ventrals, and extends 
nearly to the base of the caudal. The caudal fin adds 0°5 of an inch to the 
length of the fish. 
Head.—The orbit is large, and situated above the posterior part of the jaws; 
the post-orbital region is large. The operculi, rounded posteriorly, are well 
developed, but the constituent parts cannot be thoroughly identified in these 
specimens. The mandible is long and straight, equal in length to that of the 
body; the bone is strong and slightly thicker than that of the upper jaw; the 
latter equals the lower one in length; both are armed with small, straight, 
sharply-pointed teeth, with larger ones at intervals of about 0-2 of an inch. 
There are twelve to fourteen of the smaller between each of the larger. The 
dentition of both jaws is similar, differing in this respect from R. furcatus, 
Agassiz. ‘There are a number of branchiostegal rays, which are long and 
slender. 
The spinal column consists of thirty-six to thirty-eight vertebre; they are 
small, about as long as broad; the articulating surfaces are deeply concave, and 
the central part much contracted. The neural and hemal spines correspond 
posteriorly ; interneural spines support the dorsal; and interhemal the anal fin. 
The ribs are slender and long, with numerous apophyses. 
The dorsal fin is placed midway between the head and the caudal fin; its base 
extends 0°3 of an inch along the dorsal surface; it is composed of fourteen rays, 
the three anterior ones not so long as those following. The anal fin occupies a 
position immediately in front of the caudal, and is supported by sixteen rays, 
which are articulated to a corresponding number of interhzmal spines. The 
caudal fin is deeply cleft, with about twenty-six rays divided between the two 
lobes. The rays are articulated and dichotomize. 
The pectoral fins are large, supported by fourteen to fifteen rays, 0°8 of an 
inch in length; they divide and become filamentous at their distal extremity. 
The fins are low down on the abdominal surface of the body, the inferior 
rays of the two being joined on the median line of the abdomen; they are 
