Short, broad, no divisions of body evident; spicules closely adpressed to body and thickly overlaid; oral shield divided; radula large, distichous with 20-30 rows, teeth heavily sclerotized, each tooth with a large lateral denticle and one or more smaller median denticles on a broad base.
Syntypes: ALBATROSS Stn 4369: CAS 021401, 021402, spicule slide and
serial sections; wet specimen, MCZ.
Description: A short, stout species up to 7.4 mm long x 2.3 mm wide (to 10 mm long, Schwabl, 1963), length/width index 3.2-3.5; mantle cavity distinctly set off from trunk by sharply reduced width; oral shield not known; dorsoterminal sense organ present, but not evident except in sectioned material. Spicules deeply embedded in cuticle over entire body and forming ring around mantle cavity. Spicules long, all 10 µm thick, slightly curved towards body, with very short, sharp keel at tapered distal end, taper more or less abrupt; often longitudinally grooved on either side of raised medial section; narrowest from dorsoanterior region, up to 440 µm long and 58 µm wide; mid-dorsally and dorsoposteriorly to over 500 µm long and up to 87 µm wide; shorter ventrally, many <400 µm long, to 87 µm wide. Radula with up to 30 rows, lateral denticles up to 135 µm long, medial denticles single, up to 72 µm long, distance between inner edges of denticles at base 41 µm (Fig. 2.7B, C) to about 53 µm (holotype).Most specimens taken from the Santa Maria Basin were from muddy silts with 66% or
more silt and up to 31% clay; one specimen was collected from sandy silt having 34% sand.
Distribution: An upper continental slope species from off Oregon to Southern California Bight
between 200-600 m, except to 1,830 m south of Santa Cruz Island. Schwabl (1963) reported a depth range in the Southern California Bight of 140-810 m.