459 
furrows ; umboiial fold very excentric and oblique ; byssal fold obsolete ; byssal 
sinus probably narrow and long ; anterior end rounded, with the foldings of its dorsal 
margin numerous but not strongly marked ; no wing, or oar ; posterior end rather 
produced ventrallv, semi -truncate, with a short incomplete wing (when ])erfect) ; ventral 
margin broadly r'ounded ; umbo elevated, deep, much incurved, and acute, its cavity 
hollow; adductor impression very oxcentric, concentrically ridged; pallial impression 
marked by a series of vertically impressed fibre scars ; surface with a largo number of 
radiating and bifurcating cost© ; the intercostal spaces, or valleys, crossed by fine con- 
centric lines of growth, convex in the direction of the dorsal margin, 
Ohs. By a scries of specimens with the shell preserved, and another of internal 
casts in the Collections of IMessrs. T. W. E. David and G-. Sweet, I have satisfied myself 
that the peculiar east described by Mr. E. Etheridge, E.E.S., as Orenatula ? gilhosa is that 
of the left valve of this species. Imperfect examples only are now figured (PI. 22, figs. 
8 and 9), but in a supplementary work on Queensland Palaeontology, a complete set of 
illustrations wdll be giveji. The right valve is not known with certainty. 
In the outward form of the left valve this species resembles a Orgplima, especially 
in the overhanging sharp umbo. It also presents some features like those of Uinnites, 
and some Oysters with hollow umbonal cavities. The peculiarities of the hinge structure 
are best seen in the internal easts, such as figured by Mr. Etheridge, under the name 
of Orenatula? gibhosa, and in which the infilling of the hollow umbonal cavity is always 
well displayed. In fact, the short, almost triangular area seems to form a kind of shelf 
aci’oss the cavity of the valve similar to that in some proboseidiform rostrate oysters. 
The dorsal margin of this species is in the loft valve much arched, widening out 
below the umbo into .a more or loss concave somewhat triangular cartilage area, exeon- 
trically divided by the umbonal fold as an oblique prominent ridge, the anterior half 
of the area being thus much the smaller. The byssal fold is practically obsolete, and 
the anterior crenulations of the dorsal margin but little developed. In casts the 
triangular outline of the area is more pronounced, and the umbonal fold is represented 
by an oblique groove. 
To some extent the typical Maccoyella hinge structure is not at first apparent in 
this shell, but its generic affinity becomes apparent when viewed in connection with 
that of M. mihonalis. 
The adductor impression is always large, and well to the posterior side. 
It is possible that the impression of a very convex valve (PI. 22, fig. 9) from 
Maryborough may be referable here. It possesses eighteen chief ribs, with smaller 
intermediate ones, straight, regular, and apparently non-spinous. The concentric 
lamiuffi are strongly marked, and the finer and more delicate parallel wrinklings equally 
apparent. 
Loc. Mount Corby {The late Bev. W. B. Clarke) ; Bungeworgorai Creek, near 
Mount Abundance (Cr. Sweet — Colin. Sweet, Melbourne); Blythe’s Creek, near Blythes- 
dale Station {G. .S'ircc!!— Colin. Sweet, Melbourne) ; Lake Eyre, South Australia {Prof. 
B. Tate — Colin. Adelaide University). 
Maccoyella ? stjestriata, iloore, sp., PI. 22, fig. 10, ? PI. 23, figs. 8 and 9. 
■A-v-icula suhstriata, Moore, Quart. Journ, Geol. Soc,, 1870, xxvi., p. 247, t. 11, f. (>• 
Sp. Char. Shell of medium size. Left valve very convex or subangular in 
the middle line longitudinally; posteriorly very alate and extended; dorsal margin, 
or hinge-line, very long on the posterior side, but on the anterior oblique from the 
umbo forwards, and much thickened, folded, and crumpled, forming a wide byssal 
sinus ; posterior end very wide, alate, and extended ; umbo prominent, and probably 
