219 
furrows ; the surface of these folds is oruamented with hue parallel strite. 
Unlike what is usually the case, these folds are broadest nearest the beaks. 
The test is relatively thick, and generally transformed into a limestone spar. 
I do not know its internal structure. 
Dimensions . — The length is twenty-four, breadth twenty-four, and 
thickness fifteen, millimetres. 
Relations and Differences . — Of all the species of Pacliydomiis known 
to me, there is only P. intrepidus [Astartila intrepida) Dana, of which the 
surface folds bear any resemblance to those of the shell in question. But 
this species is larger, more elongated and relatively thinner ; its test also 
appears to be thinner. I dedicate this pretty species to the learned naturalist 
who was one of the first to describe a large number of the Palaeozoic fossils of 
Australia. 
Horizon and Localities . — The species, as yet, has only been found in a 
greyish sandstone at Wollongong. 
Genus — MiEONIA, J. D. Dana} 
M/EONIA Konincki, W. B. Clarke. 
PJ. XIX, Pig. 6. 
This is a large, very tumid and elongated, very inequilateral, suboval 
shell, a little truncated posteriorly. The valves are gibbous, the hinge-line 
very long and arched ; the anterior margin is short and joined to the inferior 
margin by a curve of small radius ; the ventral margin is slightly curved, 
longer than the hinge-line, and slightly sinuous in adult individuals ; the 
posterior margin is rather regularly curved, and joined to the adjacent margins 
without any decided boundary between. The beaks are thick, very ol)tuse 
and placed very anteriorly. Under the freaks the margins are strongly 
depressed so as to form a deep pit that could not l)e mistaken for a lunnle as 
it has no ajopreciable limit. The test has a mean thickness of three millimetres, 
except on the edges, which are sharp, and towards the beak where it is a little 
thicker. The surface is very nearly smooth, the ornamentation consisting 
^ [For a discussion of the generic value of Maonia, Pachydomus, Notomya, see Stoliezka, Cret. Fauna S. 
India (Pal. Iiidica), 1871, p. 8.3 ; K. Etheridge, Junr., Cat. Austr. Foss., 1878, pp. 71, 72 ; Geol. and Pal. Q’land., 
1892, pp. 282, 28.3.— W.S.D.]- 
2 G 
