Black Devil Snails Have A Relatively Large, Shell, Reaching To 9 Cm (~3.5 Inches) In Length But Usually Averaging About 5 – 6 Cm (~2 – 2.5 Inches). The Average Shell Width Ranges From 0.5 – 2 Cm. Shell Color Is Black In Juveniles, Turning To Mahogany (Black And Brown In Color) As The Shell Grows. The Shell Is Elongate, Smooth-surfaced And Comprises Of Around 6 To 20 Straight-sided To Slightly Inflated Whorls Inflated Towards The Aperture Side. The Adult Shells Often Have Eroded Apical Whorls. The Aperture Is White And Ovate.