Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 517 
0-3 inch from the superior margin; it is of a moderate size. The opercular bones 
are imperfect; the lower posterior margin extends backwards in an obtusely 
triangular form; its inferior margin is rounded, and is prolonged forwards to a 
considerable extent. 
The spinal column consists of twenty-seven vertebrae, of which number 
thirteen are caudal. ‘They are of moderate size, slightly longer than high. The 
ribs are hidden beneath scales. The neural and hzmal apophyses are short but 
strong. The interneural spines are slightly thicker and longer than the neural, 
and extend along the dorsal surface from a position immediately behind the 
occipital portion of the head to the peduncle of the tail. The interhzemal spines 
can only be seen by the impression beneath the scales which cover them. The 
anterior ones supporting the spines of the anal fin are large and powerful. The 
termination of the spinal column is without any upward curvature, and numerous 
small rays support the caudal appendage. 
The dorsal fin consists of fourteen large spinous rays 0°6 or 0:7 inch in 
length; the diameter at the base is 0:13 inch, which gradually becomes smaller 
and ends in a finely-pointed apex. The rays are hollow for a considerable 
portion of their length; they are separate and extend a length of 2-2 inches 
on the dorsal surface, commencing immediately behind the head; in addition 
there are eight articulated rays which are immediately contiguous to the last 
spinous ray and extend to the peduncle of the tail. The anal fin is situated 
posteriorly : it consists of seven spinous rays and ten articulated ones, without 
division into two portions or fins. The anterior spinous ray is short, strong, 
and pointed; it is 1°2 inch in front of the tail. The succeeding rays are 
longer, attaining 0°7 of an inch; they are similar in form and structure to those 
of the dorsal fin. The articulated rays extend to the base of the caudal fin and 
are repeatedly dichotomized. ‘The caudal fin is deeply bilobed, composed of 
numerous fine rays, articulated and bifurcating. A considerable number of 
rudimentary rays form an imbricated support to the outer rays of each lobe. 
The pectoral fin was attached to the bones of the scapular arch at one-third 
the height of the body above the ventral surface. The fin is absent, but an 
impression of the basal portion of its rays remain. ‘The ventral fin is abdominal ; 
it is 2°2 inches in front of the tail, and 1:0 inch behind the inferior margin 
of the operculum. It is closely folded and compressed against the ventral 
surface of the body, so that its character, or the number of rays constituting 
it, cannot be seen. 
The scales are moderately large, less than 0:1 inch in height; the posterior 
margin is circular, with a slight median point, which, however, cannot be in 
all cases detected. The edge of the scale is otherwise smooth; the surface is 
slightly pitted. There are about twenty-five scales in a transverse row running 
diagonally between the dorsal and ventral surface. The width of each scale on 
TRANS. ROY. DUB. SOC., N.S. VOL. Ill. 4B 
