Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 501 
from every other species hitherto described; and, whilst its general resemblance 
to the members of the genus Paleeobalistum leaves no room to doubt its relationship 
with that genus, there is every probability that it is a separate species, and the 
name Paleobalistum ventralis is suggested to distinguish it. 
Formation and Locality.—Hard chalk: Hakel. 
£z coll.—Natural History Department, British Museum. 
Incerta sedis. 
Chondrosteus ? 
(PL sony. fig. 1) 
A single specimen, consisting of only a portion of the tail, of a large 
chondrostean fish has been found by Mr. Lewis. It consists of the posterior 
portion of the upper and lower lobes; the former is 6°0 inches and the latter 
7-0 inches in length. The distance between the extremity of the two lobes is 
9:0 inches. There are twelve rays, with a total diameter of 1:2 inch in the 
upper lobe. ‘The external ones are somewhat shorter and smaller than the 
median ones. Along the whole of the inner margin of the fin a large number 
of fine rays extend obliquely from the large ones already mentioned. The large 
fins are much subdivided towards their extremities. The lower lobe is similarly 
forward to the upper one. There are only eight large rays, with rudimentary 
rays supporting, and filamentary rays on the posterior surface. 
Formation and Locality.—Hard chalk: Sahel Alma, Mount Lebanon. 
Ex coll.—Lewis Collection, Natural History Department, British Museum. 
Microdon ? pulchellus, Davis. 
(Pl. xx1v., fig. 3.) 
A small fish, of a rounded form, 1:3 inch in length, exclusive of the tail, 
and 1 inch in height. The tail is nearly half an inch additional. The fish is 
well preserved, and exhibits the anatomical structure as well as a considerable 
portion of the scaly covering. 
The head extends backwards from the snout 0°45 of an inch, about one-third 
the entire length of the body. The orbit is superior and large. The supra-orbital 
bones are not well preserved; the region is small. The operculi are elongated 
and narrow, smooth on the surface, and apparently without serrations on the 
margin. The mouth is placed obliquely. The mandible is 0°3 inch in length; 
its dentition is not exposed. The snout is obtusely pointed; the profile ascending 
with a gracefully-rounded curvature to the base of the dorsal fin. 
TRANS. ROY. DUB. 800., N.S. VOL, III. 8Z 
