164 
cally granose-vermiculate, remainder radiately ribbed. Ribs 
regular, prominent, increasing in strength with the growth 
of the shell, interstices deeply gouged, in breadth equalling 
the ribs, on the last whorl numbering about 45. Umbilicus 
oblong, narrow, and deep. Aperture oblique, lunate-ovate, 
lip expanded and reflected, margins united by a notched, cal- 
lous film. 
Maj. diam., 12 mm. : min. diam., 10 mm. : height, 6 mm. 
The nearest relation to this seems to be .-1 ngasella lyapil- 
Iftsa, Tate, which is larger, with fainter radial sculpture. 
Hah. — Mount Davies, Tomkinson Ranges, and Mus- 
grave Ranges. 
Xanthomelon asperrimum, ii. sp. 
Shell depressed, acutely carinated, narrowly perforated, 
thin, dull. Colour, uniform chalk white. Whorls four, 
flattened above, spire plane or elevated. Suture wound under 
the peripheral shelf of earlier whorls. Last whorl descend- 
ing in front. Sculpture : The first whorl and a half finely sha- 
greened, on the rest of the shell large and prominent grains 
are thickly set in anterior and posterior curves, which inter- 
sect each other at right angles. At the periphery the shell is 
pinched into a broad projecting keel. Base inflated. Um- 
bilicus deep and narrow. Aperture oblique, lip sharp and 
thin, a little expanded, columella arching over part of the 
umbilicus. Margfins united by a callus band. 
Maj. diam., 20 mm. : min. diam., 16 mm ; height, 9 mm. 
The peculiar form of this species amply distinguishes it 
from its congeners. The influence of desert conditions on the 
sculpture of the shell, such as are shown by this species, has 
been lucidly discussed bv Dr. Dall (Proc. Acad. Philad., 
1896, , p. 411). 
Hah. — Mann Ranges. 
