Coherent Identifier About this item: 20.500.12592/v201d6

Journal of the Asiatic Society of Bengal Part II (Natural History &c.) 1870




Hence the suture of the last whorl rises rapidly behind the constriction runs for a short distance in front of it parallel with the preceding suture and finally again ascends to the margin of the peristomo. [...] This copstriction of the whorl marks of eourse the position of the operculum when the animal is fully withdrawn into the shell and the operculum of dead specimens is also to be found at this point. [...] Behind the costriction the inside of the whorl appears thicker and is much more polished ; with the constriction this contracts leaves the outer surface of the shell and continues as a rim like the sharp thread of a screw running down and round the columella terminating on the columellar margin of the peristome in the more8 Descriptions of flew species of Diplommatinee. [...] Possibly the extremity of the foot carrying the operculum travels along the screw-like thread and the ridge above may give the necessary guiding surface to the operculuA when the animal issues from its shell. [...] 4 the interior of the shell from the loft hand side where t. represents the spiral rim ; o the position of the constriction ; r the upper ridge or tube.



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