84 
ACTING PTEEYGII. 
the present writer loc. cif., exhibits the broader end of a dental 
plate much like that just defined, near the remains of the mandible. 
In the same specimen a concave dental plate of similar structure is 
clearly observed fixed to the base of the cranium. This imperfect 
fossil and another mentioned below have thus been provisionally 
ascribed to Pletliodus obloyigus, and exhibit the cranial characters 
noted in the diagnosis of the genus given above. 
Form. Loc. Cenomanian and Turonian : S.E., England. 
49895. Imperfect head with opercular apparatus, described and 
figured loc. cit. p. 359, pi. xiv. fig. 2; Lower Chalk, 
Dorking. Capron Coll. 
The following dental plates, exhibiting the characteristic 
structure of Pletliodus, are not specifically determined :— 
P. 7279. Portion of very thick concave (upper) plate; Cambridge 
Greensand. Jesson Coll. 
P. 7280-81. Two portions of concave (upper) plates, the second 
remarkably thickened on the aboral face; Cambridge 
Greensand. Jesson Coll. 
35395. Another very concave specimen, almost longitudinally 
keeled ; Cambridge Greensand. Purchased, 1859. 
P. 6452. Small concave plate, with raised longitudinal ridge on 
aboral face ; Grey Chalk, Dover. Becldes Coll. 
The following species has also been named, but is not represented 
in the Collection :— 
Pletliodus furcatus, A. S. AYoodward, Proc. Geol. Assoc, vol. x. 
(1888), p. 331. Cliimcera furcata, A. Eritsch, Pept. u.. 
Eische bohm. Kreideform. (1878), p. 16, woodc. fig. 40. 
—Turonian ; Bohemia. [Imperfect dental plate ; Eoyal 
Bohemian Museum, Prague.] 
A cranium not yet clearly distinguished from that of Pletliodus 
has also been described as follows :— 
Byntegmodus altus, E. B. Loomis, Palseontogr. vol. xlvi. (1900), 
p. 253, pi. xxii. fig. 9.—Upper Cretaceous (Kiobrara 
Group); Kansas, U.S.A. [Imperfect cranium; Palaeon¬ 
tological Museum, Munich.] 
