PYCNODONTIDiE. 
207 
being four scales, of which the first two are described and 
figured by the present writer in Proc. Geol. Assoc, vol. ix. 
(1890), p. 297, pi. iii. figs. 30, 31; Stonesfield Slate, 
Stonesfield. Egerton df Enniskillen Colls. 
Mesodon tenuidens, A. S. Woodward. 
1890. Mesodon tenuidens , A. S. Woodward, Proc. Geol. Assoc, vol. xi. 
p. 300, pi. iii. fig. 29 (erroneously named latidens in text). 
Type. Eight splenial dentition ; British Museum. 
A small species known only by the splenial dentition. Teeth 
finely rugose, with a transversely elongated apical pit; all or nearly 
all the teeth broader than long. Principal teeth on splenial bone 
at least twice as broad as long, arched, and inwardly tapering; 
this series flanked within by one row, and externally by four rows 
of small teeth passing forwards into two rows. 
Form, df Loc. Bathonian : Oxfordshire. 
47983. Type specimen; Stonesfield Slate, Stonesfield. 
Presented by the Eon. Robert Marsham , 1877. 
Mesodon lsevior, Fricke. 
1846. Pymodus didymus , G. von Munster [errore), Beitr. Petrefakt. 
pt. vii. p. 41, pi. ii. fig. 26, pi. iii. fig. 6. 
(P) 1864. Pycnodus hugii, H. Credner (errore), Zeitschr. deutsch. geol. 
Ges. vol. xvi. p. 244, pi. xi. fig. 7. 
1875. Mesodon Icevior, K. Fricke, Pakeontogr. vol. xxii. p. 364, pi. xix. 
figs. 9-12, pi. xx. figs. 1, 2. 
Type. Splenial dentition. 
A species of moderate or large size, known only by the dentition. 
Teeth irregularly rounded in outline, with an apical pit very shallow 
in the principal series, and with feeble radiating rugse. Vomerine 
teeth closely arranged; those of the median series not much 
broader than long, and their breadth about equalling that of the 
two lateral series; outer lateral series scarcely smaller than the 
inner, and often flanked by an incomplete supplementary row of 
minute teeth. Teeth of principal series on splenial bone much 
broader than long and inwardly tapering; flanked within by one 
continuous and one incomplete series of small teeth ; and flanked 
externally by three series, of which the inner equals the outer in 
size, and the median is sometimes in part duplicated. 
Form, df Loc. Upper Corallian and Kimmeridgian : Hanover. 1 
1 The fragments from the Kimmeridgian and Portlandian of N. Prance 
ascribed to this species by Sauvage (Bull. Soc. Geol. France, [3] vol. viii. 1880, 
p. 529, pi. xix. fig. 4) appear to be incorrectly determined. ^ 
f f fl/. fd #3. S. *j. P. ELI vr-t, J>. ^'^8. 
