84 
ACTIN' 0 PTER Y G II. 
the present writer loc. cit 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 *■ 
clearly observed fixed to the base of the cranium. This irnpd'f' 
fossil and another mentioned below have thus been provisional \ 
ascribed to Plethodus oblongm , and exhibit the cranial charade t~ 
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 " 
The following dental plates, exhibiting the characterise 
structure of Plethodus, are not specifically determined : — 
P. 7279. Portion of very thick concave (upper) plate; Cambridn 
Greensand. Jesson Co 
P. 7280-81. Two portions of concave (upper) plates, the scc ° n ^ 
remarkably thickened on the aboral face; Cambri g e 
Greensand. Jesson Co 
35395. Another very concave specimen, almost longitudinally 
keeled; Cambridge Greensand. Purchased, 1 
P. 6452. Small concave plate, with raised longitudinal ridge^ ° n 
aboral face ; Grey Chalk, Dover. Bechles Co 
The following species has also been named, but is not represented 
in the Collection : — 
Plethodus furcatus, A. S. Woodward, l’roc. Geol. Assoc, v£ d‘ 
(1888), p. 331. Chvncera furcata, A. Eritsch, Dept. ’ 
Fische bohm. Kreidcform. (1878), p. 16, woodc. fi£- j 
Turonian; Bohemia. [Imperfoct dental plate; Dcj 
Bohemian Museum, Prague.] 
A cranium not yet clearly distinguished from that of Plethod * » 
has also been described as follows : — 
Syntcgmodus altus, F. B. Loomis, Palteontogr. vol. xlvi. ( L^ 
p. 253, pi. xxii. fig. 9. — Upper Cretaceous (Niob r ‘ 1 ^ 
Group) ; Kansas, U.8.A. [Imperfect cranium ; Pal* 10 
tological Museum, Munich.] 
