Memoirs of the Indian Museum. Vol. VII No. 2. Observations on the Shells of the Family Doliidae

The contrasted whiteness of the non-maculated portions of the ribs is partly due to the opaque appearance caused by the thickening of the shell substance, while the bluish appearance of the intervals is partly caused by their thinner substance allowing the porcelain-like effect of translucency ; nevertheless, whenever the specimens are sufficiently fresh, it can be readily ascertained that the col [...] The increase is due to the appearance, one at a time, of an additional rib at the anterior limit of the convexity of the base, just along the edge of the terminal zone of accre- tions. [...] The ribs are ribbon-like, and become more crowded and somewhat narrower towards the anterior limit of the base, in consequence of which the intervals, which throughout the greater part of the body-whorl are broader than the ribs, become, towards the anterior extremity, of about the same width as the ribs or narrower. [...] It is divided into two sub-equal portions, a posterior one corresponding with the accretions of the deep indentation of the notch, across which the lines of growth are deeply concave, and an anterior portion corresponding with the accretions of the anterior border of the notch and anterior termination of the shell, across which the lines of growth are convex. [...] As is usual in the shells of this genus, the external ornamentation is reproduced in the interior of the shell in inverted relief, so that it is the sunken intervals or grooves of the outer surface which assume the appearance of ribs on the internal walls.