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SIRENOIDEI. 



1878. Ceratodus polymorphus, L. C. Miall, Monogr. Siren, and Crossopt. 



Ganoids (Mon. Palaeontogr. 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. & 



Phil. 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 0*085, 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 reaching the internal margin. 



A long series of figures of the dental plates of this species is 

 given by Miall, op. cit. 



Form. Sf Loc. Rhaetic : Gloucestershire and Leicestershire, 

 England ; Wurtemberg. 



All the following dental plates were obtained from the Rhsetic 

 Section of Aust Cliff, 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. 



EnnisTcillen Coll. 



P. 4438. Plaster casts of sixteen specimens ; originals in the Higgins 

 Collection. Ennisleillen 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, 1 853-54. 



35002-4, 35007, 36387. Five specimens. Purchased, 1860, 1862. 



41287. Narrow dental plate. Purchased, 1869. 



42721. Very broad triangular dental plate. 



Presented by H. N. Moseley, Esq., 1871. 



P. 3393. Six specimens. Enniskilhn Coll. 



