434 A. Smith Woodward—On Athrodon, a Pycnodont Fish. 
tain to Mesodon or Athrodon, and in these cases the form of the 
symphysis must be relied upon. The teeth themselves are mostly 
smooth and rounded, sometimes in part mammillated. 
If, as seems probable, the characters of the splenial dentition 
suffice to determine the species of Athrodon, seven forms are now 
known to the present writer. Besides the two French species Dr. 
Sauvage has already recognised the occurrence of a third in the 
Kimmeridgian of Hanover (A. Witte); another has been described 
by Cornuel from the French Neocomian under the name of Pycnodus 
profusidens; one new species occurs in the Purbeckian, and another 
in the Cenomanian of England; and there is evidence of a third 
new species in the Senonian of Belgium. These may be enumerated 
as follows :— 
1. Arnropon Dovvitet, Sauvage. 
Bull. Soc. Géol. France [3] vol. viii. 1880, p. 530, pl. xix. fig. 5. 
Type. Left splenial bone ; School of Mines, Paris. 
The type species. Splenial bone longer than broad, with very 
small, widely spaced teeth, mostly circular and conspicuously 
mammillated, disposed in from 7 to 10 irregular series, somewhat 
enlarged towards the symphysial margin of the bone. 
The dentition of the type specimen measures 0-019 in maximum 
width and 0-045 in length. 
Form. and Loc.—Lower Portlandian ; Boulogne. 
2. ATHRODON BOLONIENSIS, Sauvage. 
Bull. Soc. Géol. France [3] vol. viii. 1880, p. 531, pl. xix. fig. 6. 
Type. Right splenial bone ; School of Mines, Paris. 
Splenial bone comparatively elongated, with large, widely spaced 
teeth and few intercalated small teeth, mostly circular and con- 
spicuously mammillated, disposed in about 4 to 6 series, scarcely 
enlarged towards the symphysial margin of the bone. 
The dentition of the type specimen measures 0-027 in maximum 
width and 0-057 in length. 
Form. and Loc.—Lower Kimmeridgian; Brecque-recque, Boulogne. 
3. ATHRoDON Wirtet, Fricke, sp. 
H. EH. Sauvage, Bull. Soc. Géol. France [3] vol. viii. 1880, p. 531. 
Mesodon Witter, K. Fricke, Paleontogr. vol. xxii. 1875, p. 364, pl. xix. fig. 16. 
Type. Imperfect right splenial bone. 
Splenial bone with small, widely spaced teeth, mostly circular 
and feebly mammillated, disposed in about 7 or 8 irregular series, 
of which that next to the innermost forms a relatively large principal 
series. 
Form. and Loc.—-Lower Kimmeridgian ; Hanover, 
4, ATHRODON INTERMEDIUS, sp. nov. Pl. XVI. Fig. 1. 
Type. Left splenial dentition; British Museum (No. 40314). 
Splenial bone comparatively elongated, with large, closely-arranged 
teeth, mostly smooth and nearly circular, a few exhibiting an apical 
pit with feebly crimped margin, disposed in about 6 or 6 irregular 
