66 WEALDBN AND PURBECK FOSSIL FISHES. 



Purbeck formations. The dentition is so variable that snch fossils can only be 

 provisionally named. 



A restoration of the skeleton of a small species, Cvelodus costae, based partly on 

 specimens in the British Museum (nos. P. 1671, P. 1071 a, P. 4394), partly on 

 figures by Bassani and D'Erasmo, 1 is given in Text-fig. 24. 



1. Coelodus mantelli (Agassiz). Plate XV, figs. — 11. 



1827. " Palates of au unknown fish," G-. A. Mantel], Foss. Tilgate Forest, p. 58, pi. xvii, figs. 26, 27. 



1833. Pycnodus microdon, L. Agassiz, Poiss. Foss., vol. ii, pt. i, p. 17. 



1839-44. Pycnodus mantellii, L. Agassiz, torn. cit.. pt. ii, p. 196, pi. lxxiia, figs. 6 — 14. 



1839-44. Gyrodus mantellii, L. Agassiz, torn, cit., pt. ii, p. 234, pi. lxixa, fig. 18. 



1853. Glossodus mantellii, O. Gr. Costa, Atti Accad. Pontau., vol. vii, p. 28. 



1856. Coelodus mantelli, J. J. Heckel, Denksclir. k. Akad. Wiss., math.-naturw. CL, vol. xi, p. 203. 



1895. Coelodus mantelli, A. S. Woodward, Catal. Foss. Fishes B.M., pt. iii, p. 252. 



Type. — Jaws; British Museum. 



Specific Characters. — A species of small or moderate size known only by the 

 jaws and dentition which rarely exceed 2 cm. in length. All teeth smooth, with a 

 shallow apical pit, which in unworn specimens is faintly crenulated round the 

 margin. Teeth of median series on vomer somewhat more than twice as broad as 

 long, with a concave posterior margin, sometimes mesially constricted; teeth of 

 two lateral series nearly equal in size, often slightly elongated antero-posteriorly. 

 their width together not equalling that of the median series. Teeth of principal 

 series on the splenial bone about twice as broad, as long, scarcely tapering inwards, 

 slightly raised at their outer end; their width scarcely equalling that of the two 

 outer series, of which the innermost is nearly twice as wide as the outermost ; the 

 inner of these teeth more or less raised at the inner end ; a seines within the 

 principal series rarely represented even by scattered small teeth. Initial anterior 

 end of splenial narrow, with the teeth in three regular series. 



Description of Specimens. — The original portions of dentition in the Mantell 

 Collection, described by Agassiz, are rightly identified as belonging both to the 

 vomerine and splenial bones, and. exhibit most of the principal characters of the 

 species. One specimen showing the narrow splenial dentition of a young indi- 

 vidual, with three regular series of teeth, is also described under the name of 

 Gyrodus mantellii. All these fossils were obtained from the Wealden (presumably 

 Tunbridge Wells Sands) of Tilgate Forest, Sussex. 



The largest known specimen of the vomerine dentition, already figured by 



Agassiz, torn, cit., pi. lxxiia, fig. 12, is shown enlarged in PI. XV, figs. 6, 6a-c. 



The median teeth are well spaced and all are worn by mastication except the 



1 F. Bassani and G. D'Erasmo, " La Ittiofauna del Calcare Cretacico di Capo d'Orlando presso 

 Castellammara (Napoli)," Mem. Soc. Ital. Sci. [3], vol. xvii (1912), pi. v, figs. 4, 5. 



