Pilsbry 1907. Manual of conchology; structural and systematic. With illustrations of the species. Founded by George W. Tryon, jun. Second series: Pulmonata. Vol. 18, Achatinidae: Stenogyrinae and Coeli-axinae. [In four parts (69-72). Pt. 72.] (Conchological dept., Acad. nat. sci.), Philadelphia, 1907: (273-357 + i-xii)