[Proc. Eoy. Soc. Victoria. 27 (N.S.).. I'l. 1.. 1914 . 



Akt. V. — On a New Species of Ceratodus from the 

 Cretaceous of New South Wales. 



By FREDERICK CHAPiMAN, A.L.S., Ac. 



(Palaeontologist to the National Museum, Melbourne.) 



(With Plate v.). 



[Read 14th May, 1914]. 



Introductory. 



The specimen now described is an opalised tooth of Ceratodus, 

 from the Upper Cretaceous of Walgett, X.S.W. It was presentL'd m 

 the National Museum by T. C. Wollaston, Esq.. of Glenelg. S.A. 

 The external surface of the tooth has been remarkably well pre- 

 served during the opalisation process, even to the minutest pittings 

 and rugosities. During replacement, the precious opal has infilled 

 the hollow portions of the tooth with amorphous mineral. l)ut 

 the external part is faitlifully replaced, as it still shows, in some 

 places to the depth of 8 mm., the vasodentinal structure as clearly 

 as in a recent tooth of Cerafodus. The tooth is somewhat imperfect, 

 having lost approximately 6 mm. of the anterior denticle, and a 

 small flake from the posterior denticle. 



Description of Ceratodus (^Metaceratodus)^ wollastoni, subgen. 

 and sp. nov. 



This tooth, including a portion of the splenial bone, comes from 

 the right side of the mandible, or lower jaw. It carries four den- 

 ticles which, in their directly normal arrangement, are like those 

 of the living Ceratodus (Neoceratodus) forsferi, Krefft. The inner 

 border is more strongly convex than in the Jurassic species. C. 

 avus. Smith Woodward, 2 but exhibits parallel, longitudinal grooves, 

 as in that form. The grinding surface is nearly flat, or only slightly 

 convex, and shallow sulci extend from between the bases of the 

 denticles nearly along the entire surface to the inner margin. 

 The grinding surface, moreover, is roughened by a regular series 



1 New subgenus to include the Australian Mesozoic species. See note at end of paper. 



2 Ann. Mag. Nat. Hist., ser. 7, vol. ,\viii., 1906, pp. 1-a, pi. i., figs, la, b. Reprinted in Rec. 

 <5eol. Surv. Victoria, vol. ii., pt. 2, 1907, pp. 135-137, pi. xiv. 



