A Manual of Conchology / According to the System Laid Down by Lamarck, with the Late Improvements by De Blainville. Exemplified and Arranged for the Use of Students.

by Thomas Wyatt

T. niloticus. The large marble Trochus.

Species not umbilicated, conical, with base flat and circular; the columella twisted; the aperture very angular.

T. obeliscus. The obelisk Trochus.

Species not umbilicated, conic, elevated, flat and circular base; the termination of the columella strongly twisted, but passing down by the margin, appearing sloped by the advance of an internal longitudinal plait.

T. iris. The iris Trochus.

Species not umbilicated, conic, base oblique; aperture large, slightly angular; the columella twisted, and forming a kind of tooth at its termination.

T. granulatus. The granulated Trochus.

Conic, imperforate at the base, spirally granulated and not marginated at the edges of the volutions; body swelling out; spire tapering abruptly; apex acute, flesh-coloured.

T. umbilicaris. The umbilicated Trochus.

Shell conico-convex, rather flat, rounded at the top; apex depressed, volutions sub-marginate; striated spirally; aperture compressed and angular; umbilicus large, extending to the apex; colour whitish.