6. Genus Conus. Pl. [XII].

Animal. Elongated, much compressed, involute; foot small, oval, long, widest in front, where it is edged by a transverse furrow; head tolerably distinct; tentacula cylindrical, having the eyes near their summit, which is setaceous; mouth at the bottom of a long labial trunk; a somewhat short tongue, although projecting into the visceral cavity, and bristled with long styliform hooks in two rows.

Shell. Covered with a periosteal membrane, thick, solid, involute, conical; summit of the cone anterior, spire slightly projecting, or not at all; a very narrow longitudinal aperture; external edge straight and trenchant; the internal also straight with oblique folds in its anterior portion; a very small horny operculum, subspirated, with a terminal summit. Found in the Australian and Mediterranean seas. One hundred and eighty-one species.

FAMILY XXII.
Nautilacea. Two genera.

1. Genus Spirula. Pl. [XII].

Animal. Body elongated, cylindrical, terminated posteriorly by two lateral lobes partially concealing the shell; head provided with five pairs of tentacula, of which two are longer than the others.

Shell. Very symmetrical, longitudinally twisted throughout nearly all its extent; the cone spiral, conical, regular, circular; whorls of the spire very evident; partitions simple, concave, and pierced by a single syphon. Inhabits the West Indian seas. One species.