449 
Psetidomonotu, and does not agree withthe peculiar Bivalve for which Beyrich* instituted 
the latter genus — viz,, Monotis speluncaria, Sehl. Broni Stoliczka’s species, O. rochwood- 
ensis differs in its much greater size, larger number of cost®, presence of the smaller inter- 
polated ones, and an increased convexity of the surface ; nor do I tliink that it is in 
any way connected with Moore’s Avicula simples, \ A. ceqiialis (PI. 24, fig. 3), or his 
Area (?) plicala (PI. 24, fig. 5), as our shell is much too generally globose, and 
possesses a different posterior wing, and on the whole, appears to agree better with 
the left valve of Oxyfoma than with any other genus. Of some of those supposed 
species I have seen the types in the Bath Museum, and can only say that the species 
are founded on wretchedly small and most unsatisfactory material. Oxytoma is a 
typical Avicula, but more inequivalve, with a very deeply cut byssal sinus close under 
the anterior auricle of the right valve; the left valve, on the other hand, should be 
convex, or even globose, sharply ribbed, or echinated, and with a somewhat deeply cut 
posterior wing. O. rockwoodensis is no more convex about the umbonal region than 
the Oolitic Oxytoma echinata, Sby. 
Loc. Kockwood Station, Landsborough River (ii. L. Jack) ; Aramac {The 
late James Smith). 
Oxytoma ? simplex, Moore, PL 24, figs. 2-5. 
Avicula simplex, Moore, Quart. Journ. Geol. Soc., 1870, x.vvi., p. 247, t. 11, f. 3 {? f. 4). 
,, (nqualis, Moore, loc. cit., t. 11, f. 4 (? f. 3). 
Area pl'icatciy Moore, loc, cit.f p. 249, t. 12, f. 6. 
Syj. Char. Shell small, very inequilateral. Left valve convex, thickened about the 
Umbonal region ; right valve flattened, plain. In the left valve the cardinal margin or 
hinge line straight, long. Posterior wing very extended ; anterior wing small. Surface 
with seven or eight sharp, well-separated radiating costae and a few concentric laminae. 
Ohs. In describing Avicula simplex and A. aequalis, Mr. Moore would 
appear to have transposed the numbers of the figures representing these fossils in the 
eleventh plate. Uis definition of A. simplex corresponds not to fig. 3, as stated, but 
to fig. 4, and vice versa; the description of A. cequalis is applicable to the latter 
figure, and not to the former. The types of these so-called species are in the Bath 
Museum, and have been examined by me. Both are very small shells, and the original 
of Moore’s fig. 5 {A. simplex as it should be) is fairly w'ell represented. But the type 
of his fig. 3 (J. (z?^jwZ2,9 in reality) is a very obscure specimen, and is more correctly 
represented in our PI. 24, fig. 2. It is the opposite valve to Moore’s fig. 4, and may 
quite well represent its right valve ; in fact, if this is so, it will fairly well accord with 
what takes place in other species of Oxytoma. 
I cannot see on what possible grounds Moore separated from the foregoing a 
small shell termed by him Area plioata. There is no evidence of its Arca-af&nitj ; but 
having the entire outward appearance of 0. ? simplex, I have united it with the latter. 
Loc. Wollumhilla {The late Lev. TV. S. Clarke); Minmi, near Roma {L. L. 
Jack). 
Genus — PSEUI) AVICULA, gen. nov. 
Gen. Char. Shell in general outline meleagriniform, but devoid of an anterior 
wing or ear. Valves compressed, closed, nacreous within, bi-convex, inequilateral. 
Cardinal margin thin, no area, or hinge teeth, but probably with a small ligament. 
Posterior wing moderately developed, but with little or no emargination. Adductor 
4auscular scars subcentral, of medium size. 
2 E 
* Zeitsoh. Dentschen Geol. Gesellsch., 1862, xiv., p. 10. 
t Quart. Joiirn, Geol. Soc., 1870, xxvi., 1. 11, f. 3. 
