254 PROCEEDINGS OF THE GEOLOGICAL SOCIETY.
49. Myacites planus, sp. n. Pl. XII. fig. 10.
Shell thin, ovately elongated ; umbones rather anterior, depressed, close ; anterior margin attenuated ; posterior side most convex, with an obtuse slope to a moderately rounded margin ; inferior margin rounded ; the dorsal surface possesses transverse interrupted lines of growth, with, in the interspaces, numerous fine concentric striae.
From Wollumbilla ; only one example is known.
50. Nucula Cooperi, sp. n. Pl. XII. fig. 8.
Shell trigonal, very convex ; umbones rather anterior, widely separated ; anterior side angular, posterior side rather produced and attenuated ; ventral margin rounded.
This shell, for a Nucula, attains considerable size. It is named after Sir Daniel Cooper, Bart., late Speaker of the Sydney House of Assembly.
It is from Wollumbilla.
51. Nucula Truncata, sp. n. Pl. XII. fig. 9.
Shell triangular ; umbones anterior, compressed ; anterior side very truncated; dorsal margin rounded; hinge-line with about seven large teeth on the posterior side of the umbo, and with four or five on the anterior side.
Only a single specimen of this shell occurs. It is readily distinguished from N. Cooperi by its more compressed form and truncated margin.
Loc. Wollumbilla.
52. Thracia Wilsoni, sp. n. Pl. XIV. fig. 8.
Shell thin, transversely ovate, slightly inequivalve, compressed ; umbones obtuse, anterior ; anterior side short and roundly truncated, posterior side rounded and angular ; ligament external, anterior to the umbones ; dorsal surface covered with very fine irregular wavy lines of growth, which become oblique on the posterior margin.
The right valve possesses a slight sinus towards the centre of the ventral margin, with a corresponding elevation on the opposite valve. Two specimens of this shell have been found. Breadth 3 inches, height 2-1/4 inches.
One is from the Amby river, the other from the Bungeeworgorai creek. It is named after J. R. Wilson, Esq., of Bungeeworgorai.
53. Tancredia Plana, sp. n. Pl. XIII. fig. 13.
Shell thin, smooth, flattened, transversely ovate, rather inequivalve ; anterior side rounded : posterior margin oblique ; surface of the shell covered by very fine transverse striations.
The matrix contains portions of Avicula &c.
Only one example is known. It is from Blythesdale, fifteen miles from Wollumbilla.
54. Trigonia Moorei, Lycett, sp. n.. Pl. XIV. figs. 9 & 10.
[Allied to T. costata, but has the general figure more ovate and
