Davis— On the Fossil Fishes of the Chalk of Mount-Lebanon. 613 
in height; it diminishes anteriorly to the termination of the jaws. The orbit is 
situated very high: it is large, and little more than half an inch in front of the 
posterior margin of the operculum. The opercular bones are large, and rounded 
posteriorly. ‘The upper jaw expands backwards beyond the orbit, and descends 
so as to envelop the posterior portion of the lower jaw. Only a slight trace of 
teeth can be distinguished: they are small, conical, and pointed; others of larger 
size may be hidden by the matrix. 
The vertebral column is composed of thirty-nine or forty vertebra, of which 
sixteen are caudal. The anterior vertebre are larger than those behind; the 
larger are 0°2 inch long and 0:15 inch high. Strong ribs, with branching 
apophyses, with a slight curvature backwards, are attached to each abdominal 
vertebrae. Similar spinous processes extend from the neural and hzemal surface 
of the posterior vertebree ; hzemal spines are also attached to the anterior vertebree. 
Interhzmal bones support the anal fin, and interneural the dorsal. 
The dorsal fin extends 2:0 inches along the surface of the back; it is 2°5 
inches behind the head, and its posterior rays 1:5 inch before the tail; it has 
twenty rays; the basal portion of these is preserved; they are strong, with 
articular base for attachment to the interspinous bones. So far as preserved they 
are undivided. The anterior rays are thicker than those following. 
The anal fin consists of seventeen rays, each attached to an interhemal spine ; 
it is much smaller than the dorsal, the rays thin and apparently short; its 
anterior rays are 2°0 inches before the caudal, and it has a basal extension of 
1:5 inch. 
The caudal fin is not well preserved; its lobes are widely expanded and 
short. It consists of twenty-four rays attached to a somewhat expanded hypural 
bone; the rays are jointed at short intervals. A series of rudimentary rays 
support both the upper and lower lobe of the tail. 
The pectoral and ventral fins are not well preserved. The former are located 
on the ventral surface immediately behind the head; only a remnant of a base 
is preserved. The ventral fins are 3 inches behind the pectorals ; they appear to 
be comparatively small; they are separated by a distance of 1:0 inch from the 
anal fin, and are opposite to the middle portion of the dorsal. 
The evidence of scales is slight, and no estimate of their form or size can be 
made. The bones of the head are enveloped in thin brown enamel, which also 
extends over the surface of the jaws. 
A large jaw of this species of Rhinellus is represented on Plate xxxvil., fig. 7; 
it is the mandible, or lower jaw, measuring 5 inches in length; at its base it is 
0:35 inch broad; it is straight, and contracts in breadth towards the anterior 
extremity, which terminates in a point. The surface of the jaw is raised into 
a series of converging ridges, which coalesce towards the point; one or two 
of the larger ridges are broken so as to form a serrated line. The anterior 
TRANS, ROY. DUB. SOC., N.S. VOL. 11D. 40 
