Longchaeus conicus is a species of sea snail, a marine gastropod mollusk in the family Pyramidellidae, the pyrams and their allies.

The early whorls are flesh-colored; the later ones light brown with an occasional varix of flesh color.

They are depressed helicoid, having their axis almost at right angles to that of the succeeding turns, in the first of which they are about half immersed.

The thirteen whorls of the teleoconch are decidedly flattened, slightly shouldered and weakly crenulated at the summit.

The entire surface of the spire and the base is marked by numerous exceedingly fine lines of growth only.