HORN EXPEDITION—MOLLDSCA. 
193 
the columella on the body and over the umbilicus is excessive ; columella arched. 
Umbilicus wide and deep, about one-fourth the diameter of the base. 
The ground colour is a pale brown, varied by three rufous bands, one at the 
suture, one adjacent to the periphery on the upper face, and one subperipheral. 
Sculpiure .—The two apical whorls (relatively large) are minutely granulated ; 
the rest of the surface is ornamented with elevated, compressed, acute, arched ribs; 
the intercostal spaces densely granulated ; the ribs on the body-whorl number 
about forty, and are continued from the suture into the umbilicus as shallow 
sigmoid curves. 
Dimensions. —Diameters, 17 (with lip 18) and 15 ; height, 18; height of last 
whorl behind anterior deflection, 7 ; width of umbilicus, 4-25. 
Locality .—On the southern slope of the escarpment, bounding Horn Vnlley 
on the south, at the Finke Gorge on its eastern side. Dead shells in vast abund¬ 
ance, but only a few individuals taken alive beneath the large loose blocks of 
sandstone after a couple of hours’ toil. 
The specific name, arcigerens (bow-bearing), is in allusion to the arched costie. 
Affinities .—This shell exhibits a somewhat similar sculpture to T. silve7'i, 
T. kooringensis, T. kordaensis, Angas, approaching in shape most to the last, but is 
flatter, less angulated, and the cori ugations r(\gular, sharply elevated and distant. 
From all it differs by its expanded aperture, reflection of the outer lip, and exten¬ 
sive deflection of the united margins of the peristome, in which particular it 
assimilates to T. grandituherculata, mihi. 
Chlopitis squamulosa, Tate. (Plate XVIII., Fig. 10.) 
Reference —Hadra squamulosa., Tate, Trans. Roy. Soc. S. Aust., vol. xviii., 
p. 193, 1894. 
Shell depressedly subglobose, regular convex on the side and broadly convex 
below; spire short. Whorls five, of moderate increase, moderately convex, 
separated by a well-defined suture. Last whorl roundly flattened at the suture, then 
broadly curved to the base, not at all inflated, rather abruptly descending a little 
at the aperture. Aperture nearly circular, its plane obli(|ue to the vertical axis of 
the shell; peristome incomplete, its margins moderately approximating and united 
by a thin callus, the outer lip slightly everted, columella dilated and reflected over 
the umbilicus. Umbilicus about one-fifth of the width of the base, somewhat 
abruptly descending, its margin being somewhat flatly rounded. 
EB 
