Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 477 
Family. SPINACIDZ. 
Genus. Spinax. 
Each dorsal fin with a spine. Teeth of the lower jaw with the teeth so 
much turned aside that the inner margin of the tooth forms the cutting edge. 
Upper teeth erect, each with a long-pointed cusp and one or two small ones 
on each side. Spiracles wide, superior behind the eye. (Giinther.) 
Spinax primevus, PricTet. 
[‘‘ Desc. de quelques Poiss. foss. du Mont. Liban.” (1850), p. 53, pl. x., figs. 1-3.] 
(PL xv1., fie. 2.) 
M. Pictet described and figured three fragments which he attributed, with 
some hesitation, to the above species. Figure 3 (op. cit.) is a fragment of a fish 
exhibiting the second dorsal fin, and is without spine. The head (figure 2, op. cit.) 
may or may not belong to a fish of this species; it is sufficiently indefinite to 
render the question doubtful. A comparatively perfect specimen, collected by 
Mr. Lewis, and now in the Natural History Museum at South Kensington, 
exhibits the true characters of the fish. It is 11 inches in length from the tip 
of the snout to the extremity of the tail. The greatest height is 1°2 inches 
behind the head; the peduncle of the tail is 0:4 of an inch. 
The spinal column is well ossified; the vertebre in the anterior part of the 
body are 0°125 of an inch in length, and their height is equal to two-thirds 
their length ; they gradually diminish in size backwards, and at the extremity 
of the caudal series they are quite minute. The articulating surfaces are 
expanded, the intermediate median portion much contracted. The number of 
vertebre is 96. 
The head is 1°5 inches in length. The snout, prolonged nearly 0°5 of an inch 
beyond the buccal orifice, is more or less depressed, wide, and rounded. The 
mouth is large, extending 0°8 of an inch backwards, and armed with teeth 
whose base is rather less than 0:1 of an inch in breadth; a central cusp is promi- 
nent, half the basal breadth in height, and leaning backwards in the form of 
a flattened cone; on each side the central cone there are two or three minor 
cusps or denticles. The only teeth exposed are situated on the posterior portion 
of the jaws. The whole of the head, as well as the remaining portions of the 
body, are covered with dermal tubercules. Position of the orbit not defined. 
There are two dorsal fins, each supported by a spine. The spine of the 
first dorsal is 3:5 inches behind the snout; the base of the fin extends 1 inch, 
TRANS, ROY. DUB. $O0C., N.S. VOL, III, 38U 
