lis FOSSIL FISHES OF THE ENGLISH CHALK. 



longitudinal wrinkles, which cause splits in the enamel of the fossils; the acute 

 edges not serrated. Symphysial extremity of each dentary bearing three large 

 fceeth, and its oral border toothless where apposed to the dentigerous part of the 

 splenial; splenial with two large teeth, and smaller teeth in front but none 

 behind ; vomerine teeth inclined backwards. 



Description of Specimens. — The detached and imperfect teeth to which the 

 name Protosphyrxna ferox was originally given, are obviously insufficient for exact 

 specific determination, but they agree well enough with those found in direct 

 association with the long, round rostrum described in the foregoing diagnosis to 

 be identified with it. They are the commonest teeth of Protosphyraena from the 

 English Chalk, and are indeed likely to belong to P. ferox as now defined, because 

 the long and round form of rostrum is much more abundant in the same deposit 

 than the other forms described below. 



As rrroved by a specimen from Cuxton, Kent, prepared by Mr. F. Harford 

 (Brit. Mus., no. P. 5651), the middle of the cranial roof is flattened, shows no 

 sutures, and is ornamented with a close network of fine ridges which tend to run 

 most conspicuously in an antero-posterior direction, and are often subdivided or 

 raised into rounded tubercles. The flattening of the roof is continued on the base 

 of the rostrum, in front of the insertion of the vomerine teeth, and the character- 

 istic reticular ornament extends forwards quite to the anterior end. The rostrum 

 (PI. XXXI, fig. 1) is straight and slightly directed upwards from the front of the 

 skull. At its base (fig. lu) it is deeper than wide, with a flattening of the top as 

 already described, and a constriction below in front of the vomerine teeth. At 

 this point its upper half is hollow, and the inner cavity is divided by a vertical 

 median partition. Further forwards the rostrum becomes round in section for 

 the rest of its length ; while the internal cavity soon loses its partition and 

 becomes relatively larger (fig. 1 b), though eventually disappearing at some 

 distance from the anterior end. The relatively small vomerine bones (v.) evidently 

 form the elongate-triangular prominence on the lower face of the rostrum at its 

 base, but they are so completely fused that their limits are indistinguishable. 

 From the abrupt hinder face of the prominence a pair of rather short and broad 

 teeth project with a backward inclination. These teeth are fixed in sockets, and 

 are not always of equal size, suggesting that they were renewed by alternate 

 development. They are best seen in a fragment described by W. Davies, loc. rib., 

 fig. 3. 



The premaxilla (PI. XXXI, figs. 2, 3) is not completely known, but it is 

 elongate-triangular in shape, Avith the acute apex forwards. Its outer face 

 (fig. 2) is flattened in front, slightly convex behind, and ornamented with a 

 rugosity like that of the rostrum. The thickest part of the bone is the oral 

 border (fig. 2a), where the wide ledge is pitted with at least seven deep and 

 complete sockets for teeth. The teeth are largest in the middle of the bone, 



