MOORE — AUSTRALIAN MESOZOIC GEOLOGY. 245
shell ; its chief peculiarity appears to be its very high and conical
figure in proportion to its size.
It is from Wollumbilla.
9. Rhynchonella rustica, sp. n. Pl. X. figs. 7-9.
Shell variable, usually wider than long ; beak acute ; when young, compressed, with both valves slightly convex, without sinus, and margins rounded ; with age, the shell is furnished with a broad sinus in the ventral, with a corresponding convexity or mesial fold in the dorsal valve ; surface covered with striae, from 20 to 25 in number, which in the adult shell are somewhat wavy or irregular.
With age the dorsal valve becomes very convex, and the frontal margin considerably thickened. It approaches most closely to the Rh. concinna of the Great Oolite and Bradford Clay ; but in its general aspect it is a coarser shell, and the plicae are more irregular. I have seen about twenty examples, so that it must be very abundant. In the hollows of the striae are occasionally Polyzoa, and attached Foraminifera.
It is from the Wollumbilla district.
10. Rhynchonella solitaria, n. sp. Pl. X. fig. 10.
Shell wider than long ; ventral valve with broad mesial sinus, in which are four widely spreading costae, with a single lateral costa on either side of the sinus. Towards the umbo the shell is smooth, and without appearance of costae.
Only a single specimen of a ventral valve of this species occurs, in one of the Wollumbilla blocks ; and this is not quite perfect.
11. Terebratella Davidsonii, sp. n. Pl. X. figs. 1 & 2.
Shell rather large, transversely ovate or subtrigonal, slightly convex ; beak truncated ; ventral area extended and slightly depressed below a lengthened, slightly rounded hinge-line. The surface of the valves exhibits distinct but very minute punctations, and possesses wide concentric bands, on which are regular, but much finer, lines of growth ; these are crossed by numerous radiating striae, which, towards the margins of the folds, give the shell a fimbriated appearance, very fine plicae being visible on the whole of the surface. The larger or dorsal valve possesses a wide mesial fold, with a corresponding sinus on the ventral valve.
Three examples of this very pretty species occur, but only one is free from the matrix and tolerably perfect.
From the Wollumbilla drift-boulders.
12. Avicula Barklyi, sp. n. Pl. XI. figs. 1 & 2.
Shell slightly inequilateral, orbicular ; large valve convex, small valve flattened, umbones prominent ; auricles rather small, nearly equal.
The large valve is slightly produced posteriorly, and is ornamented by about 24 radiating costae, which are more raised and appear
