a: Parietal view
b: Palatal view
A door snail's closing apparatus or clausiliar (Clausiliidae) often is an important part of systematical (taxonomical) determinations and the distinction of different door snail species. The different sides are the parieto-columellar side (frontal or apertural view) and the palatal side (back side) of the shell. The armature on the parieto-lamellar side are called lamellae, while one the palatal side they are called folds (plicae).
Upper lamella oder parietal lamella (sul), and spiral lamella (spl). Lower lamella (Columellar lamella, il) and Subcolumellar lamella (scl). The area between upper and lower lamella is called interlamellar. At the suture between whorls a parallel lamella (pll) is often found. The clausilium is made of a stem (cs) and a plate (cp).
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a: Parietal view |
b: Palatal view |
Principal fold (pri), upper palatal fold (up). If a lunella is present, the palatal fold has a frontal (anterior upa) and a rear (posterior, upp) part. Middle palatal fold or lunella (lun), lower palatal fold (lp), is a lunella is present, again with a frontal (Basalfalte bas) and a rear (Subclaustralis, scs) part. Lowest palatal fold (Sulcalis sulc). If subclaustralis and sulcalis are joined together, only the description rear (posterior) palatal fold should be used. Near the suture between whorls there often is a sutural fold. The callous thickening of the rear wall behind the aperture is called a palatal callus.
Source: Hartmut Nordsieck auf: hnords.de.