266 
SIRENOIDEI. 
1878. Ceratoduspolymorphus , L. C. Miall, Monogr. Siren, and Crossopt. 
Ganoids (Mon. Paigeontogr. Soc.), p. 28, pi. ii. figs. 1-13, pi. iii. 
figs. 1, 2, 5, pi. iv. figs. 1-11, pi. v. figs. 1, 5. 
1889. Ceratodus latissimus, A. S. Woodward, Trans. Leicester Lit. & 
Pliil. Soc. n. s. pt. xi. p. 21. 
Type. Lower dental plate ; Bristol Museum. 
The type species. Dental plates robust, attaining a maximum 
length of about OOSo, usually much longer than broad, varying in 
shape from triangular to oval and oblong ; inner margin more or less 
sharply angulated ; coronal surface generally sinuous, sometimes flat, 
and deeply pitted. Denticles four in the mandibular dental plates, 
four and a rudiment or five in the palatine, the ridges being low and 
rounded, ill-defined, and not reachiug the internal margin. 
A long series of figures of the dental plates of this species is 
given by Miall, op. cit. 
Form. Sf Loc. Bhaetic: Gloucestershire and Leicestershire, 
England; Wlirtemberg. 
All the following dental plates were obtained from the Bhsetic 
Section of Aust ClifP, near Bristol. The mandibular are distinguished 
from the palatine not merely by the absence of a fifth denticle, but 
also frequently by the prismatic form of the most anterior denticle, 
this being adapted to two grinding surfaces. 
(i.) Upper dental plates. 
P. 4438 a. Plaster casts of four specimens and two associated dental 
plates, figured by Miall, op. cit. pi. iv. figs. 1, 3, 4, 7, 8; 
originals in the Higgins Collection, Bristol Museum. 
Enniskillen Coll. 
P. 4438. Plaster casts of sixteen specimens ; originals in the Higgins 
Collection. Enniskillen Coll. 
23153. Small imperfect dental plate. Purchased, 1849. 
28280. Seven examples. Purchased , 1853. 
28495, 29035. Three specimens, one having an only gently sinuous 
external margin. Purchased , 1853-54. 
35002-4, 35007, 38387. Five specimens. Purchased, 1860, 1862. 
41287. Harrow dental plate. Purchased, 1869. 
42721. Very broad triangular dental plate. 
Presented by H. N. Moseley , Esq., 1871. 
Enniskillen Coll. 
P. 3393. Six specimens. 
