184 
Ophileta subangulata, spec nov. Plate ii., figs. 8a-b. 
Shell minute, concave above, smooth, composed of two rapidly 
increasing whorls, which are in contact but not embracing. The 
periphery of the last whorl is compressedly rounded, the upper 
surface slightly declining from it to about two-thirds the breadth, 
thence steeply sloping to the suture ; this sudden change of slope 
simulates a keel in the anterior one-third of the whorl, producing 
a slight concave slope between it and the periphery. Base 
tumidly convex. 
Dimensions.—Major and minor diameters, 3° and 1:5 re- 
spectively. 
Locality. — Cambrian limestone at Parara, near Ardrossan 
(several examples). 
The two species of Ophileta, figured by Etheridge, Proc. Roy. 
Soc., Tasmania, 1863, tab. 2, figs. 13, 14, from the Cambrian or 
“ Caroline Creek beds ” of the Mersey River District, Tasmania, 
are very different from the one here described. 
Platyceras primevum, Billings, seen from above, as figured 
by Shaler and Foerste, Bull. Mus. Comp. Zool., 1888, p. 30, 
tab. 2, fig. 10, has the general outline of Ophileta subangulata, 
but the last whorl is “throughout evenly rounded,” and more- 
over is devoid of the submedial angulation. Despite the simili- 
tude, I do not think the two species are congeneric. 
Platyeeras Etheridgei,spec. nov. PI. ii., figs. 7a-7e. 
Shell small, broadly conical ; apex obtuse, posterior, recurved, 
but not spiral, usually protruding beyond the posterior margin ; 
aperture roundly oval, but irregular in outline, subtruncated and 
narrowed posteriorly. Surface ornamented with rather thick sub- 
imbricating concentrie folds of growth, and curved beneath the 
apex coincidently with the posterior margin; faintly radially 
wrinkled. 
This very common species exhibits considerable variability in 
the outline of the aperture, and the amount of backward projec- 
tion of the apex. The shells seem to have lived on irregular 
surfaces, and in some instances at least upon trilobites. 
Dimensions.—The proportionate measures of the basal 
diameter and height are as 4 to 3; the longest diameter observed 
is 6 mills. 
Locality. —Curramulka, in Cambrian limestone. 
The species is dedicated to Mr. R. Etheridge, junr., who has 
contributed so largely to the elaboration of the Cambrian fauna 
of Australia. 
The irregularity of its margin and less-tumid sides distinguish 
P. Etheridget from P. Dawson, Walcott. 
