Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/352

244 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. length of the shell ; umbones depressed ; ventral area extended ; deltidium narrow, triangular ; exterior of the valves covered with coarse rounded striae, which are broken at the concentric lines of growth, where they are seen to be hollow, and were probably continued in spines over the folds of the shell ; exterior of dorsal valve abruptly keeled, the lines of growth crossing, which give the keel a comb-like appearance ; interior of the dorsal valve with a sinus, which terminates at the front of the shell in a deep fold ; and it possesses teeth-sockets, cardinal process, and distinctly raised crural plates ; ventral valve, in its younger state, rather flat, but becomes concave and closely fitting to the dorsal valve; it possesses a deep sinus corresponding to the depression in the interior of the large valve ; edges of the shell closely fitting ; internal loop not known.

Shell-structure very finely punctated. This interesting shell is found with the Purisiphonia and other remains at Wollumbilla ; and as there are evidences of several more or less perfect examples in the block, it must be an abundant shell. It belongs to the group originally arranged by Dr. E. Deslongchamps under Argyope, of which he described three species from the Lias, but which, in his ' Paleontologie Francaise,' he subsequently removed to Terebratula. Having found the same species at Whatley, and referred them to Argyope, I think it convenient still to retain them in this group, though ultimately it is probable they may have to be separated from it and constituted a subgenus. At present little is known of their loops or internal characters. The Australian examples are more regularly striate than the European Liassic species. Where the striae on the A. wollumbillaensis are occasionally abraded, a canal is visible, which leads me to suspect they were originally hollow, and probably continued in spines beyond the shell, like those on Athyris or Spirifera rostrata. In its outer form this shell very much resembles some of the Strophomenidoe.

7. Argyope punctata, sp. n. Pl. X. fig. 6.

Shell small, transversely ovate ; dorsal valve flattened or slightly convex ; margins regularly rounded ; surface of valve with bifurcating longitudinal strias, which at the front are thirty in number.

This shell clearly indicates the presence of a second species of this group. Only one valve is known, and this is not perfect. The striae are much more distant, and stand up in sharp ridges, and the punctations are much coarser and fewer than on the A. wollumbillaensis. In these respects the species approaches nearer to the French and English examples.

The specimen is from Wollumbilla, and is attached to the surface of a Serpula intestinalis!

8. Discina apicalis, sp. n. Pl. X. fig. 13.

Shell small, round or slightly ovate ; apex very acute, almost central, or inclined to anterior end ; shell-structure thin, with faint concentric lines of growth.

I have only seen a single, somewhat imperfect, example of this