HORN EXPEDITION—MOLLUSCA. 
185 
sublevaia and T. adcockinita. The final climatic pliasc was the creation of the 
“ Dry Zone,” which eftectually cuts off migration in a soutlierly direction. The 
limited community of species of the areas north and south of the axis of the “ Dry 
Zone” is the result of migration prior to its existence, as is partly evidenced l>y 
the fact that, over much of the country from Ooraminna Pass to Crown Point, 
Badistes fodinalis occurs in vast numbers in a subfossil state, where shelter from 
soil or herbage is non-existent; with it occurs in places Pupa coniraria. The 
desiccating climate may have killed off many of the molluscan inhabitants of this 
region, whilst the survivors found refuge in the rocky fastnesses of the country. 
These main deductions I have set forth in my Report on the Botany of the 
Expedition, and the facts of the distribution of the land mollusca lend them some 
support. Like the truly endemic plants, the land snails live on the southern 
escai'pments of the elevated land, or in the deeply-shadowed gorges of the same, 
and occur in very constricted areas, sometimes as one colony only, or, if in more, 
then usually widely-separated from one another, thus Liparus spenceri, Angaselhe 
(except A. setigern), Glyptorhagadce, Badistes 2 vatfii, B. grandituberculata^ Thersites 
sub/evata, and Charopce, were each found constituting a single colony; but in the 
aggregate the species are distributed over a few thousand square miles. 
3. Descriptive List of Species. 
Family Endodontidj^. 
Micpophyura hemiclausa, Tate. (Plate XVII., Fig. 1.) 
Reference— Planispira hetniclausa, Tate, Trans. Roy. Soc. S. Aust., vol. xviii., 
p. 192, 1894. 
Shell depressed, spire slightly prominent. Whorls tlu’ee and a half of very 
slow increase, somewhat gradated, irregularly convex, roundly convex anteriorly, 
rapidly declining to the broadish and shallow spiral excavation at the suture. 
Last whorl regularly convex from the sutural fuiTow to the circum-umbilical 
angulation. Aperture not deflected; lunate; peristome much thickened, con¬ 
tinuous all round, the parietal incrassation obliquely in advance and forming a 
vertical plate half-closing the aperture. Umbilicus relatively wide (about one- 
third the width of the shell), scalar within; the margin defined by an obtuse 
angulation terminating in the outer basal angle of the aperture, the side of the 
umbilicus inclines precipitously from the basal angulation. 
Colour. —Uniformly pale horn, pellucid and glossy. 
AA 
