PAL^ONTOLOCilA NOV^ CAMBRIA MKRIDIONALIS— 



OCCASIONAL DKSCRIPTIONS OF NEW SOUTH WALKS 



FOSSILS— No. 7.1 



l!V 



R. Eii(ki;iim;k, .Imii'., Director aiul Curator. 

 (Plates xxviii.-xxx.) 



PKU.Mii-CAltHONIKEKOUS MoLLUSCA. 



I. — (Jeiiiis Dielasma, Kimj, 18(51. 



(Proc. Dublin Zool. Bot. Assoc, i., 1861, p. 256.)2 



Dielasma jerv^iseiisis, xj>. imv. 



(Plate xxviii., tig. 4.) 



Sp. C'/un-.s-. — Brachial valve broad-oval, of low even convexity ; margins 

 well and evenly rounded, presenting all but a circular circumference ; 

 dental sockets small and elongate ; crura in all probability short (repre- 

 sented by their bases only) ; muscular platform well developed occupying 

 exactly one-third the length of the valve, triangular wedge-shaped ; 

 regular concentric laminae of growth, unevenly spaced apart. 



Ohs. — This is undoubtedly a very uncommon form of the genus, the 

 broad, low-convex surface, and the almost circular outline distinguish this 

 internal cast of a brachial valve from any other Dielasnia occurring in our 

 Permo- Carboniferous rocks. 



Loc. — Cabbage Tree, ten miles fi'om Jervis Bay, Shoalhaven (li. 

 Barnes). 



Hor. — Upper Marine Series. 



Dielasma in versa, de Kouinck, up. 



(Plate xxix., fig. 3 and 4.) 



Rhynchoiiella ivversu, de Koninck, Pal. Foss. Nouv. Galles du Sud, 1877, 

 pt. 3, p. 82, pi. xi., figs. 11, 11(( and b. 



Dielasma inversa, Eth. fil., Rec. Geol. Survey N.S.Wales, v., pt. 4, 1898, 

 p. 175, pi. xix., figs. 1-13. 



Ohs. — Two specimens, but neither perfect, are figured to illustrate 

 the size to which this remarkable shell attained, and the variability of the 

 folds of the brachial valve, when compared with the largest figure given 



J Continued from Vol. xi.. p. 219. 



2 Teste Marshall, Nomenclator, 1873, p. 113. In two previous publications, at 

 least. Geology and Pal. Q'land, 1892, p. 225, and Bull. Geol. Survey W.Austr., No. 

 27, 1907, p. 19, 1 gave an incorrect generic reference to King's genus. 



