PYCXODONTIDiE. 
215 
splenial from Yonne, France (H. E. Sauvage, Bull. Soc. Sci. Nat. 
Yonne, vol. xxxiii. pt. ii. 1879, p. 35, pi. ii. fig. 5) ; an imperfect 
splenial from the Lower Neocomian of Ville-sur-Saulx, Meuse, 
France (J. Cornuel, Bull. Soc. Geol. France, [3] vol. viii. 1880, 
p. 158, and ibid. [3] vol. xi. 1883, p. 24, pi. i. fig. 10) ; and frag¬ 
ments from the phosphates of Cambridgeshire and Bedfordshire 
(W. Keeping, Foss. Neocom. Fpware, 1883, p. 82, pi. i. fig. 5). 
To Mesodon may also probably be referred the portions of vome¬ 
rine dentition from the Corallian of Schnaitheim, Wiirtemberg, 
described under the names of Typodus annulatus and splendent by 
F. A. Quenstedt, Der Jura (1858), p. 781, pi. xcvi. figs. 16-18. 
A fragment of a similar vomer is ascribed to Sphcerodus by F. A. 
Quenstedt, Handb. Palseont. (1852) p. 214, pi. xvi. fig. 9. 
The undefined name of Pycnodus tristychius (L. Agassiz, Poiss. 
Foss. vol. ii. pt. ii. 1844, p. 199) seems to have been given to an 
English Jurassic jaw of Mesodon, probably from the Stonesfield 
Slate. The type specimen was originally in the Bristol Museum. 
The following form of dentition seems to be related to Mesodon , 
but is not represented in the Collection :— 
Gyronchus oblongus , L. Agassiz, Poiss. Foss. vol. ii. pt. ii. (1844) 
p. 202, pi. lx. a, figs. 10, 11. Gyronchus (ScapJiodus ) 
oblongus , L. Agassiz, ibid. vol. i. (1844), p. xlii. Sca- 
phodus lieteroniorphus , J. Morris (“ ex Agassiz, MS.”), 
Catal. Brit. Foss. (1854), p. 344 ; A. S. Woodward, Proc. 
Geol. Assoc, vol. xi. (1890), p. 301, pi. iii. figs. 33, 34. 
Mesodon oblongus, Woodward & Sherborn, Catal. Brit. 
Foss. Yertebrata (1890), p. 120.—Stonesfield Slate; 
Stonesfield. [Yomer ; Bristol Museum.] 
Genus ATHRODON, Sauvage. 
[Bull. Soc. Geol. France, [3] vol. viii. 1880, p. 530.] 
An imperfectly definable genus, known only by the splenial bone, 
which much resembles that of Mesodon , but is considerably stouter 
and exhibits a remarkably deep symphysial facette. Splenial teeth 
as in Mesodon , but usually much more irregularly arranged, and 
the principal longitudinal series not well differentiated. 
Athrodon douvillei, Sauvage. 
1880. Athrodon douvillei, H. E. Sauvage, Bull. Soc. G6ol. France, [3] 
vol. viii. p. 530, pi. xix. fig. 5. 
Type. Left splenial; School of Mines, Paris. 
The type species. Splenial bone longer than broad, with very 
