The humped tree snail (Partula gibba; akaleha, denden), in the Partulidae family, is endemic to the forest ecosystem on the Mariana Islands of Guam, Rota, Saipan, Tinian, Aguiguan, Anatahan, Sarigan, Alamagan, and Pagan. The shell of the humped tree snail can be left- or right-coiling, conic-ovate, translucent, with evenly spaced spiral sculpturing (Cowie 2014, in litt.). The color ranges from white to brown, and a pointed apex is colored rose-red, with a milky white suture. Adult snails are from 0.6 to 0.7 in (14 to 18 mm) long, and 0.4 to 0.6 in (10 to 14 mm) wide, with 4.5 whorls, the last of which is the largest (Pilsbry 1909–1910, in Crampton 1925, p. 60; Smith et al. 2009, p. 2). In general, partulid snails may live up to 5 years. The humped tree snail occurs in cool, shaded forest habitat as first observed by Crampton (Crampton 1925, pp. 31, 61), with high humidity and reduced air movement that prevents excessive water loss. Crampton (1925, pp. 31, 61) described the habitat requirements of the partulid tree snails as having ‘‘sufficiently high and dense growth to provide shade, to conserve moisture, and to effect the production of a rich humus.