PLIOSAUKUS FEEOZ. 21 



Pliosaurus ferox, Sauvage, sp. 



[Plates I. & II. ; text-figs. 1-7.] 



1873. Liopleurodon ferox, Sauvage, Ball. Soc. Geol. France, [3] vol. i. p. 378. 

 1880. Polyptyclwdon ferox, Sauvage, Bull. Soc. Geol. France, [3] vol. viii. p. 544. 

 1880. Pliosaurus ferox, Lydekker, Catal. Foss. Rept. Brit. Mus. pt. ii. p. 145. 



Pliosaurus pachyclirus, Seeley (Index to Aves, etc., in Woodwardian Museum, 1869, 

 p. 118), and Thaumatosaurus mosqueasis, Kiprijanoff (Mem. Acad. Imp. St. Petersbourg, 

 vol. xxxi. (1883) art. 6, p. 27), are perhaps synonyms. 



Type Specimen. — A tooth from the Oxford Clay of Wast near Boulogne-sur-Mer. 



The teeth in this species are circular in section, not trihedral as in the Kimmeridgian 

 species. Lydekker regards this form as probably ancestral to P. macromerus. 



All the following specimens from the Leeds Collection were obtained from the 

 Oxford Clay in the neighbourhood of Peterborough. 



R. 26B0. Xearly complete skull with numerous isolated teeth. This specimen is figured on PI. I. 



and was described and figured in Quart. Journ. Geol. Soc. vol. liii. (1897) p. 177, 

 pi. xii. The whole has been somewhat crushed from above downwards, and the bones 

 of the roof are thus somewhat difficult to determine. 



The dimensions (in centimetres) of this specimen are : — 



Length from tip of snout to occipital condyle 112-0 



,, „ „ anterior angle of external nares . 57 - 



„ ,, „ ,, „ internal nares . 36-0 



Length from tip of snout to posterior end of the facial 



processes of the premaxilla 74-0 



Length of the external nares 5-0 



„ „ internal nares 6-5 



,, posterior interpterygoid vacuities ll'O 



Width of skull between the outer angles of the quadrates 



(perhaps exaggerated by crushing) 50-0 



Width of skull at level of transpalatine hone 48-0 



„ ,, middle of internal nares 19-0 



,, „ at diastema ll - 3 



„ „ at widest part of premaxilla? 12 - 



Width of articular surface of quadrate 12-6 



Greatest (transverse) diameter of occipital condyle .... 6-5 



Teeth (PL II. figs. 2, 2 a, 2 b, 3, 4, 4 a) : Largest. Smallest. 



Length along outside of curve 23-5 6*2 



Length of crown 8-5 2-0 



Diameter at base of crown 2-8 1-1 



