PYCXODONTIDJS. 
245 
vomer depressed and flattened, conspicuously rugose, those of the 
median series not very prominent and at least equalling in width 
the two flanking series. 
Form. Sf Log. Jurassic : Russia. 
P. 3782. Type specimen described and figured by Mantell, loc. cit .; 
from Rjeff, on the Volga. The crowns of the outermost 
series of teeth are all broken away, and only one of the 
median series remains. Enniskillen Coll. 
f*OUy Gyrodus-^ cretaceus, (Xgassiz.^ 
1833-39. Sphcerodus mammillaris , L. Agassiz, Poiss. Foss. vol. ii. pt. i. 
p. 15 (in part), pi. lxxiii. figs. 1, 2. [Teeth.] 
1839-44. Gyrodus cretaceus, L. Agassiz, ibid. vol. ii. pt. ii. p. 233, 
pi. Ixix. a. fig. 13. 
1840. Gyrodus cretaceus, R. Owen, Odontography, p. 72. 
1844. Gyrodus mammillaris, L. Agassiz, ibid. vol. ii. pt. ii. p. 236. 
1844. Pycnodus marginalis, L. Agassiz, ibid. vol. ii. pt. ii. p. 199. 
[Tooth.] 
1850. Gyrodus cretaceus , F. Dixon, Geol. Sussex, p. 370, pi. xxx. fig. 15. 
1850. Gyrodus conicus, F. Dixon, ibid. p. 370, pi. xxxii. fig. 8. 
1888. Gyrodus cretaceus , A. S. Woodward, Proc. Geol. Assoc, vol. x. 
p. 308. 
Type. Portion of vomerine dentition. 
A large species of uncertain genus, probably not Gyrodus, but 
known only by fragmentary dentition. Dental crowns much elevated, 
obtusely acuminate, and coarsely rugose ; those of the median and 
outer paired series on the vomer longer than broad, about equal in 
size ; teeth of inner paired series oq this bone relativelv small and 
irregularly subdivided. 
Form. Sf Loc. Senonian : Sussex and Surrey. 
39048. Vomerine dentition figured in Dixon’s Geol. Sussex, pi. xxx. 
fig. 15 ; Chalk, Lewes. Bowerbank Coll. 
49802. Portion of vomerine dentition ; Upper Chalk, St. Catherine’s 
Hill Pit, near Guildford. Capron Coll. 
P. 6852. Portion apparently of splenial dentition, showing principal 
series of teeth ; Chalk, Upper Warlingham, near Croydon. 
Presented by G. E. Dibley, Esq., 1893. 
The following specimen seems to belong to Gyrodus , but is not 
specifically determined:— 
43285. Portion of relatively broad vomer, with well-spaced teeth 
remarkably uniform in size (PI. XVII. fig. 5) ; Kimmeridge 
