< Previous family introduction

Next family introduction >

Family  Olivellidae

Rice shells




The Olivellidae was previously classified as a subfamily of the Olividae.  The shells resemble the olives in shape and in having a high gloss, but differ by being smaller, with the aperture only one-third to one-half of the total shell length.  They were moved to their own family because of anatomical differences to the olives, particularly the absence of tentacles and eyes, the absence of accessory salivary glands, and the shape of the visceral mass.  In contrast to olives, most olivellids have a horny operculum, which covers all of the large aperture.  Regardless, the classification of the group is not agreed at family level.

The family is small in size, best represented in tropical and sub-tropical northern and southern America, with common species extending into temperate areas of eastern North America .  There are only four species in temperate eastern Australia and additional but poorly studied species in Queensland and Western Australia .

The American species live intertidally or in the shallow subtidal, on sand or mud, sometimes in large aggregations, where they are carnivores or scavengers, including small bivalves in their diet. The Australian species live in the shallow subtidal zone, down to about 100 metres, and most are uncommon, apart from the small, white Cupidoliva nympha which is common in beach drift. 

Family References:  There in no revision of the group in Australia .  The most recent work, which deals with the American species, is:

Olsson, A.A. 1956. Studies on the genus Olivella.  Proceeding of the Academy of Natural Sciences of Philadelphia 108: 155-225

Coverage:  All of the species which occur in NSW are treated here.

Identification Notes:   Olivellids have a deeply grooved suture, a character which is also found in the olives.  The columella is smooth, apart from a strong plait formed by the fasciolar band at the bottom.  The fasciolar band callus may by transparent, allowing the underlying pattern to show through, or opaque and obscuring the pattern. The fasciolar band is demarcated by the fasciolar edge ridge which commences on the inner lip of the aperture, often adjacent to the centre of the aperture.