Shell: minute to small, elongate-conic to turbiniform. Outer lip opisthocline to prosocline, with or without varix, thickened or thin, with or without denticles internally; peristome simple in most species, with or without weak posterior sinus. Axial and spiral sculpture present, sometimes spiral sculpture alone distinct; axial ribs usually continue over base but are weaker than on remainder of body whorl. Protoconch of 1 1/2 to more than 2 1/2 whorls, sculptured with raised dots to a few very strong spiral keels, often with irregular raised lines and dots in combination. Apex generally not strongly tilted in species with paucispiral protoconch.
Head Foot: cephalic tentacles long, ciliated, with parallel sides, anterior and posterior pallial tentacles present in most species; metapodial tentacles, in most species, 3-7. Anterior pedal gland present, posterior pedal gland usually inconspicuous and possibly absent in a few species.
Operculum: simple, thin, nucleus eccentric, paucispiral.

World-wide except Antarctic and Subantarctic regions. Upper Cretaceous (?) to Recent

Diagnosis. Shell minute, moderately elevated, whorls rounded, suture deep; sculpture clathrate, with axial and spiral elements; aperture simple, rounded.
Biology. Like other rissoids, species of Alvania feed on diatoms and microalgae. Eastern Pacific species have a planktonic larval stage.
Remarks. The genus is worldwide with numerous species. Ponder (1985:36) treated anatomical characters and recognized five subgenera worldwide. Eastern Pacific species were placed in the typical subgenus. The two species treated here are the only species occurring offshore in southern California.

Genus Alvania Risso, 1826
Type species: Alvania cimax (Linné, 1758)
Diagnosis: Shell, oval-conic with protoconch, paucispiral, dotted. Cancellate sculpture with spirals only at bottom. Aperture, ovate; outer lip, thin with dentition inside. Operculum without process.

The opercular, sculptural and radular characters of of Alvania are similar to those of Rissoa. The external features of the animal of species of Alvania are somewhat similar to those of Rissoa but the sole is often less distinctly partitioned into anterior and posterior segments, the posterior mucous gland is sometimes indistinct and has a relatively small opening, there are always 2 (not 1-2) pallial tentacles (anterior and posterior) and 3-7 (not 1) metapodial tentacles.