246 PROCEEDINGS OF THE GEOLOGICAL SOCIETY.
spinous on the posterior margin. The small valve is but very slightly
convex, and is very distinct in its ornamentation from the larger,
the costae being much finer and about 44 in number. The costae are
decussated by numerous regular concentric lines of growth, which,
when they meet, give them a nodulated aspect. The lines of growth
have been reflected or folded over the anterior auricle and side, which
gives the shell a very peculiar appearance. The small valve possesses
a large and deep groove for the passage of a byssus.
The punctate structure of the Aviculidae may be clearly distinguished, by aid of the lens, in this species. Sections of the shells of this genus are to be seen in almost every block from Wollumbilla ; but the above is the only specimen clear of the matrix. It is from Wollumbilla, and is named after Sir Henry Barkly, late Governor of Victoria.
13. Avicula reflecta, Sp. n. Pl. XII. fig. 1.
Shell rather inequivalve, rather longer than wide ; large valve regularly convex ; surface ornamented by about 38 radiating and slightly undulating costae, every fourth costa being rather more prominent, which are crossed by widely separated interrupted lines of growth. The surface is also decussated by thin bands of concentric striae, which terminate with a slightly fimbriated or ragged edge.
On the back of this specimen, covering the auricles and the umbo, a small valve is attached, which probably belongs to it. In its general contour it resembles A. Barklyi ; but the longitudinal costae are finer and in greater number, being as 57 to 44 in the latter ; these are decussated, as on the larger valve, by very thin wavy concentric striae.
Numerous examples of Planorbulina Ungeriana are attached to the small valve ; and a Natica, with a Lima and fragments of other Aviculidoe, are in the same block.
Loc. Wollumbilla.
14. Avicula umbonalis, sp. n. Pl. XII. figs. 2 & 3.
Shell thick, transversely ovate ; umbo produced and sharply incurved over small valve ; hinge-line extended and nearly equal on both anterior and posterior sides ; large valve convex, small valve flattened, both of which have longitudinal striae and narrow wavy lines of growth.
This species is represented by a single specimen, the test of which is imperfect. Its peculiar hinge-line clearly separates it from either of the other Australian species ; and its shell, unlike that of the Aviculidae, is comparatively very thick.
Loc. Wollumbilla.
15. Aviculla corbiensis, sp. n. Pl. XI. fig. 7.
Shell longitudinally ovate, longer than wide, nearly equilateral; umbo distinct, raised, curving over hinge-line ; posterior auricle short, anterior obsolete ; anterior margin and front regularly round-
