aperture

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Shell: Medium to large, depressed-discoidal to planorboid, spire very low with little other than embryonic whorls projecting in apertural view; final part of last adult whorl descending gently prior to aperture; whorls more or less evenly rounded, suture indented; umbilicus very wide, its margin evenly rounded; underside of embryonic whorls clearly visible.
Nucella kill and consume their prey by either drilling through the shell or wedging open the prey item's shell margin with their apertural edge (Barnett 1979, Perry 1987).
The data used to measure the three characters were based on seven apertural landmarks, which are illustrated elsewhere (Wagner 1995a, 1996).
Key to genera of Chilodontidae in the south-western Indian Ocean (applies only to specimens with mature apertural dentition)
integrifolium, apertural views show the right-hand lopha overlapping above the left (Fig.
Apical and apertural refer to directions along the spiral of the shell towards the tip or opening respectively: the columellar muscle narrows apically, but is wide aperturally.
They reported that when all other shell variables are approximately equal, gastropods with larger shells, thickened apertural lips, or sculptured shells suffered significantly fewer fatal attacks from shell-crushing crabs than gastropods with small, thin or unornamented shells.
It is a subadult specimen in which the apertural dentition is not fully developed (Fig.
Thorson (1946) illustrated several pyramidellid shells near metamorphosis and stated that the outer apertural margin of the larval shell thickens to become a new columella at metamorphosis.
Numerous shell attributes of marine gastropods can deter predation, including spines (Palmer 1979), thicker apertural lips (Kitching et al.
10 ridge-like denticles, with an additional row of smaller granules just inside lip edge; apertural dentition absent in immature specimens, in these the outer lip is strongly notched at ends of spiral cords; interior nacreous, weakly angled beneath external cords, but labral denticles not extending into aperture as in-running ridges.