408 
ACTINOPTERYGII. 
and the rostrum much laterally compressed, except towards its 
attenuated distal extremity which is round in section. The rounded 
upper contour of the rostrum gradually becoming raised into an 
obtuse median longitudinal ridge at its base and ornamented with 
coarse rugae, which frequently subdivide into tubercles and are 
mainly longitudinal in direction though partly turned obliquely 
downwards; the lateral portions ornamented with much finer 
longitudinal rugae which in part tend to converge at the middle of 
the side, and form a slight median longitudinal ridge on the inferior 
aspect of the rostrum for some distance in advance of the vomerine 
area. 
Form. Sf Loc. Cenomanian (Cambridge Greensand): Cambridge¬ 
shire. 
P. 7248. Uncrushed fragment of base of rostrum, displaying the 
upper contour and ornamentation, the pair of ethmoidal 
canals, and part of the vomerine area. Jesson CoTl. 
P. 7246-47. Five typical fragments of rostrum. Jesson Coll. 
Protosphyrsena brevirostris, A. S. Woodward. 
1895. Protosphyrcena brevirostris, A. S. Woodward, Geol. Mag. [4] 
vol. ii. p. 212, pi. viii. fig. 9. 
Type. Imperfect rostrum; British Museum. 
Bostrum comparatively short and acute, its length apparently 
not exceeding 0*05 in a specimen measuring 0025 in transverse 
diameter where the vomerine teeth are implanted. Upper aspect 
of rostrum flattened and the sides converging below in a median 
inferior keel, making the transverse section triangular at the end of 
the vomerine region ; surface nearly smooth. 
Form. Sf Loc. Cenomanian (Cambridge Greensand) : Cambridge¬ 
shire. 
P. 7253. Type specimen described and figured, loc. cit. Jesson Coll. 
P. 7252. A more abraded rostrum, with a slightly larger and longer 
extension, imperfect at the extremity hut exhibiting a 
flattened triangular area immediately in front of the 
vomerine teeth, noticed ibid. p. 214. Jesson Coll. 
Protosphyrsena depressa, A. S. Woodward. 
1895. Protosphyrcena depressa , A. S. Woodward, Geol. Mag. [4] vol. ii. 
p. 212, pi. viii. fig. 8. 
Type. Imperfect rostrum; Woodwardian Museum, Cambridge. 
Bostrum comparatively short and depressed, its length apparently 
