Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/365

MOORE AUSTRALIAN MES0Z0IC GEOLOGY. 257 63. Natica ornatissima, sp. n. Pl. X. fig. 16.

Shell small ; spire depressed ; whorls convex, the last very rounded and globose ; aperture large and circular Shell-structure smooth, with broad bands of growth at intervals, within or on the surface of which are finer striations. The shell still retains some of its original colour.

One specimen only, from Wollumbilla.

64. Rissoina australis, sp. n. P1. X. fig. 23.

Shell very small, moderately elevated, spire consisting of five rounded or convex volutions, with distinct rounded sutures, which are ornamented with numerous longitudinal costae.

This shell, which is very minute, is from Western Australia. Only one specimen has been recognized.

65. Turbo australis, sp. n. Pl. X. figs. 17 & 18.

Shell small, discoidal ; spire obtuse and much depressed ; whorls 4, the outer circumference convex ; surface with slightly curved, depressed lines of growth ; mouth large, ovate.

This shell is from Western Australia.

66. Crioceras australis, sp. n. Pl. XV. fig. 3.

Shell very large, discoidal ; whorls rounded, incurved, the inner whorls rather closely fitting but separate. In the younger state, as seen in the reduced figure, the shell possesses regular rounded slightly curved ribs with intervening rounded sulci, which increase in width with the age of the shell. In the adult shell the ribs become widely separated, the largest chamber measuring at the back 3-1/2 inches, and they possess very acute ridges, with two depressed bosses on either side, the depressions between the ribs being regularly concave.

The block containing the last five chambers of the shell is slightly compressed on the back ; and, though it is not complete, the mouth measures 7-1/2 inches in depth by 7 inches in breadth. The siphuncucular tube is small and situated immediately under the back of the shell.

There appears no reason to doubt that the larger chambers belong to the smaller whorls, though the connecting portions are wanting. When complete, it is probable the shell attained nearly twice the dimensions of the C. Bowerbankii of the Lower Greensand. Its ornamentation is proportionally much coarser than in that species.

On the interior of the shell are attached Polyzoa, Serpuloe, and other remains identical with those on the interior of the Cytherea Clarkei previously noticed, from which there appears no doubt that that shell and the Crioceras are identical in age ; and as no example of Crioceras has yet been obtained out of the Neocomian period, it is reasonable to infer that they represent it on the Australian continent.

It is from the district of the Upper Maranoa.