Hadroconus altus

(Original description by Watson) The height of the shell attains 8.2 mm. The small shell has an equilateral conical shape. It is flat-based, and sharply angulated. It is delicately sculptured, and nacreous under a thin, white calcareous surface. Sculpture : there are about 45 longitudinals. These are hair-like, strongly sinuated, flexuous, for they advance markedly at the periphery, where they are each ornamented by an elongated curved tubercle, and on the base they again retreat so as to form a sinus. On the earlier whorls these longitudinals are much more distinct than on the later, and each starts from a little bead, which lie close to the suture, but these beads are very feeble on the body whorl. In the intervals of the longitudinals and parallel to them are very faint growth lines. Above the carina two spirals are stronger than the rest, with a sharp intermediate furrow. Above these are several hair-like lines, which become feebler toward the middle of the whorl and strong again above, the upper whorls presenting one in particular, which connects the row of infra-sutural beads. On the base below the carina there are four narrow and sharp spirals, followed by about eight, which are broader and flattened, and within these is one stronger than the rest, with about sixteen rounded beads, which crenulate the edge of the umbilicus. …