Type locality: SW of Seguam Island, Aleutian Is., Alaska (52°09.22 N, 172°39.6 W). 153 m (NMFS 23-199701-80).
Description: Shell moderately large (to 109 mm, LACM 3611), pyriform, whorls rounded; white, with thick, fibrous periostracum. Nuclear whorls eroded, four to five teleconch whorls; shell thin, a fraction of a mm thick, except for strengthening along columella and in the deposition of final, flared lip. Spiral sculpture weak or absent. Axial sculpture absent. Aperture less than half of shell height, oval; canal short, broad.
Radula: Rachidian tooth nearly twice as broad as long, lateral edges rounded. Lateral teeth large, tricuspid, outer cusp thick, curved, tapering, constricted at base, forming a notch; central cusp, small, fairly thick, rather blunt; inner cusp thick, triangulär, angled inward, twice as long as central one, about 1/4 the length of outer cusp.
Remarks: This species is unique among the Beringiinae, in being very fragile, and the shell cannot be dried, because it begins to unravel at the suture and then fracture into many fragments . Treating the shell with glycerin and keeping it in a sealed bag or Container prevents this fragmenting.
Etymology: From the Latin: exilis meaning fragile or easily broken, and fragilis brittle, in, reference to the fragile, poorly calcified shell.
Distribution: Known only from the vicinity of Seguam and Amutka Passes (171° W to 173° W), at depths of 153-338 m.
Habitat: Volcanic sand bottom, with a bottom temperature of 3.7-4.4°C. Seguam and Amutka Islands are somewhat isolated islands in the central Aleutians, surrounded by deep, swift passes, Seguam Pass to the west, and Amutka pass to the east.