WOODWARD : SHARKS OF THE CRETACEOUS PERIOD. 
67 
shown of the natural size in pL II. , figs. 3-6 ; and six of the more 
cuspidate teeth from the group just mentioned are represented in 
figs. 7 a — d. 
The species thus determined on the evidence of the dentition is 
characterized by the short, robust, and obtusely pointed form of the 
cusps in the principal lateral teeth, and the acute character of the 
longitudinal keel of the crown in many of the hinder teeth. The 
anterior prehensile teeth are unknown. 
S. illingworthi has hitherto been obtained from undetermined 
horizons in the Chalk near Lewes, Sussex, and Dorking, Surrey ; and 
from the Lower Chalk of Guildford and Dover. 
Genus Cestracion. 
[Cuvier, Regne Animal, vol. ii., 1817, p. 129]. 
In the " Catalogue of Fossil Fishes in the British Museum," 
pt. i., pp. 333-336, the writer expressed the opinion that the so-called 
Drepanephorus of Egerton is generieally identical with the existing 
Port Jackson Shark {Cestracion), and that the detached Cretaceous 
teeth variously known as Strophodus sulcatus, Acrodus cretaceus, 
A. polydictyos, and A. rugosus may all be most appropriately referred 
to the same genus. Nothing subsequently discovered has tended to 
alter this determination. So rare, indeed, is the occurrence of Ces- 
traciont remains in the Cretaceous formations, that every additional 
specimen is worthy of special consideration. 
Cestracion rugosus (Agassiz). 
1839. Acrodus rugosus, L. Agassiz Poiss. Foss., vol. iii., p. 148, 
pi. 22, figs. 28-29. 
1889. Cestracion rugosus, A. S. Woodward Cat. Foss. Fishes, Brit. 
Mus., pt. L, p. 335. 
More especially rare are the large tritoral teeth from the Chalk, 
provisionally named Cestracion rugosus. Until recently the writer 
was acquainted only with two English specimens, one from Lewes and 
the other from Charing, Kent ; but the British Museum has now 
been enriched by a third example, the discovery and donation of 
Mr. G. E. Dibley. This tooth was obtained from the Lower Chalk of 
Warlingham, near Croydon, Surrey, and is shown of twice the natural 
