Lapparia Conrad, 1855.

The genus Lapparia is based on V. pactilis Conrad, a small shell with a contracted base, persistent spiral ornamentation, and a shoulder armed with sharp tubercles. A deep anterior notch to the aperture causes a prominent raised fasciole; the columella is furnished with four strong plaits decreasing anteriorly; and the nucleus is scaphelloid.

Suter (1907, p. 202) placed his species L. parki in this genus at the instance of Dall, who had examined the specimen. Later, when he had seen Dall's new section of Adelomelon—Miomelon—with a spiked nucleus and more elongated shape, he transferred his species to it, in the meantime having synonymized L. parki with L. corrugata (Hutton). The generic change was an improvement, but, as has been stated above, the New Zealand shells are more closely related to Alcithoe, and have been here given the new name of Spinomelon. Adelomelon, Miomelon, Alcithoe, and Spinomelon are probably offshoots from a common Antarctic ancestor of Cretaceous age.

The generic position of one of the shells supposed by Suter to be Lapparia hebes (Hutton), but classed below as Alcithoe angusta (Suter), is a different question. None of the specimens has a well-preserved nucleus, but in size, shape, axial sculpture, and apertural notch they show considerable resemblance to Lapparia. Spiral sculpture, however, is lacking; the columellar