136 
SELACHII. 
- 
. 
28720. Two teeth ; Cenomanian, Tournai, Belgium. 
Purchased , 1853. 
P. 1390. Six detached teeth from the same formation and locality. 
Egerton Coll. 
P. 4557. Two teeth ; Upper Greensand or Chalk Marl, Montignies, 
Belgium. Enniskillen Coll. 
42862. Three small teeth, probably of this species; Boucourt, near 
Perustetz, Belgium. Van Breda Coll. 
The following specimens are of a very coarsely marked variety:— 
4388-93, 4398, 4400, 4408,4446. Ten teeth, not improbably found 
associated ; Lewes. Mcintell Coll. 
49732. Portions of block of chalk, with 26 naturally associated 
teeth : Upper Chalk, Guildford. Capron Coll . 
49844. Three teeth, found associated ; Upper Chalk, Shalford, near 
Guildford. Capron Coll. 
35674, Detached tooth ; locality unknown. Bean Coll. 
Ptychodus rugosus* Dixon. 
1850. Ptychodus rugosus, P. Dixon, Foss. Suss. p. 362, pi. xxxi. fig. 5. 
1850. Ptychodus altior , F. Dixon ( non Agassiz), op. cit. p. 362, pi. xxx. 
fig. 10. 
Type. Detached tooth. 
The crowns of all the teeth are much elevated in the median 
portion, and marked with coarse rounded ridges. The latter are 
irregular and considerably interrupted, only about three being 
usually complete upon the transversely ridged centre. Upon the 
more finely marked surrounding area the ornament tends towards a 
concentric arrangement. 
In some of the teeth the median portion of the crown is raised 
into a high, laterally compressed eminence, with smooth sides. 
Such teeth have been described as referable to a distinct species, 
P. altior , but the examples in the British Museum prove their 
specific identity with P. rugosus. It is also not improbable that the 
teeth named P. trigeri by H. E. Sauvage 1 may belong to this 
species. 
Form. Loc. Senonian and Turonian : S.E. England. 
1 Biblioth. Ecole Hautes Etudes, vol. v. art. 9 (1872), p. 19; and Bull. Soc. 
Geol. Prance, [3] vol. vi. (1880), p. 624, pi. xi. fig. 1. Cenomanian; Dept. 
Sarthe, France. 
