8 . 
LAND SHELLS' 
S.A. NAT., 
VOT.. X'^'TTI. No. 2. 
Expedition is responsible for many of the species, and also many 
of the problems, as they lumped together specimens from the 
various places under the vague locality, Central Australia. If 
series were separately collected and studied, the variation seen, 
might be accurately determined as geographic, ecologic or indiv- 
idual. The negative features of this faunula are as notable as. 
the positive, as the Leeuwiniar^ family, Bothriembryontidae, is 
only represented by three distinct forms, two coastal and one 
interior, a fourth entering the western limit only. No Dampier- 
ian species have yet been recognised, though some may occur in. 
the north-west of this Area whence we have no molluscs. Per- 
onian peculiar forms are notably absent, especially those charac- 
teristic of the Oxleyan Sub-Area, while the Solanderian Xa 7 itho~ 
melo7i, Hadra, Sphaerospira, Austrochloritis ^ etc., are really miss- 
ing, but appear to be ancestral relatives of Sinumelon, Meraco- 
7uelo7i, Fleuroxia, Glyptorhagada, etc. 
Throughout Australia land shells prove to be apparently 
very variable and this variation does not seem at first sight truly 
geographical and has been regarded as colonial or ecological, but 
it may be due to geological formation and hence the study of 
Geozoology becomes paramount. Thus in this Centralian Area, 
the mountain ranges are separated in time as well as space and 
hence the molluscan inhabitants differ. A series from the- 
Musgrave Ranges differs decidedly from a similar series from 
the MacDonnell Range, and this does not occasion surprise when 
we know that a strong fault occurs between. Local conchologists 
must consider the geology in connection with land shells and 
also determine whether the specimens collected are truly geo- 
graphical forms or merely ecological variations. The latter will 
provide a deal of study, as these may be further divided Into- 
forms dependent on the local ground conditions, which may be 
termed geodecols, or have been produced by climatic moods 
which differ in years, the former being stable for the place, the 
latter unstable through time variation: the latter may be called 
horecols, and the determination of Australian land molluscs must 
be governed by a knowledge of all the environmental conditions, 
including the climatic. I will explain these terms more fully 
in another place. 
The excellent figures, provided by Miss Joyce Allan, of the 
Australian Museum, to whom my best thanks are again due, will 
be most useful to students as, in addition to the new species,, 
they illustrate each South Australian genus. 
