Variation of terrestrial gastropods in the Philippines in relation to shell shape and size

The bicuneate distribution of shell height (h) against maximum diameter (d) discovered in various terrestrial pulmonate faunas occurs also in that of the Philippines, but with one exceptional group, the (almost entirely) endemic He1icostylinae, which give a scatter overlapping the two usual modes and bridging the unoccupied area between them. The unrelated Papuininae in northern Australasia and nearby islands show a similar hut more restricted scatter. It is probable that ecological opportunities, taken independently by these two groups. are available in regions with tropical rain forest but not in other vegetational formations.