Amphibola Schumacher, 1817

Golding, Rosemary E., Ponder, Winston F. & Byrne, Maria, 2007, Taxonomy and anatomy of Amphiboloidea (Gastropoda: Heterobranchia: Archaeopulmonata), Zootaxa 1476, pp. 1-50 : 6-7

Genus Amphibola Schumacher, 1817

Amphibola Schumacher, 1817: 190 . Type species Amphibola australis Schumacher, 1817 (subjective synonym of A. crenata ), by original designation.

Ampullacera Quoy & Gaimard, 1832: 196 . Type species Bulimus avellana Bruguière, 1789 (as Ampullacera avellana ) by subsequent designation ( Gray 1840) (subjective synonym of A. crenata ).

Thallicera Swainson, 1840: 339 . Type species Bulimus avellana Bruguière, 1789 (as Thallicera avellana ) (subjective synonym of A. crenata ) by monotypic designation.

Ampullarina Sowerby, 1842: 64 . Type species Bulimus avellana Bruguière, 1789 (as Ampullarina avellana ) (subjective synonym of A. crenata ) by monotypic designation.

Diagnosis: Shell diameter to 35 mm, thick, grey to light brown, exterior roughened, shoulder on last whorl square, spire short; umbilicus wide with fold or plait adjacent to aperture in some specimens, columellar callus sometimes present; sinus notch raised and square. Operculum thick, brownish-red, entirely corneous, elongate, with paucispiral nucleus at base of columellar edge; inner surface of operculum with slightly raised, incomplete spiral around nucleus. Head and foot dark grey to black in formalin-preserved specimens. Opposed ciliary tracts running full length of mantle cavity. Hypobranchial gland anterior to kidney approximately 1/4 mantle length, dark red, raised to form rounded dome, with numerous black-pigmented ducts leading to embedded glandular cells. Radula with central tooth, inner and outer lateral teeth, approximately 30 marginal teeth on each side of radula; central tooth of radula with hexagonal, flattened mesocone; inner lateral teeth narrow, bicuspid; outer lateral teeth with three cusps, marginal teeth elongate, narrow, curved. Central nervous system euthyneurous, with cerebral and pleural ganglia connected by distinct commissure; subcerebral and parapedal commissures present; visceral loop long, with accessory ganglion present between left parietal and visceral ganglia. Seminal vesicle occupying upper hermaphrodite duct, highly folded and coiled; seminal receptacle unpigmented. Spermoviduct folded, with hairpin-bend distally. Spermovipositor cylindrical; spermoviduct continues through spermovipositor forming narrow duct opening beneath shallow hood at tip; second duct opens near end of spermovipositor but is blind ending internally; spermovipositor lacking microsculpture. Thin walled spermovipositor sheath enclosing spermovipositor, lacking pouches. Prostatic gland proximally lined with epithelium comprising short secretory cells. Egg mass approximately 3 cm diameter, semi-circular or collar shaped, elliptical in cross-section.

Remarks: A relatively large amount of descriptive information has been published on the type species, A. crenata (e.g. Farnie 1919). Other taxa attributed to Amphibola are of uncertain affinity (see Incertae sedis section). The generic diagnosis was thus formulated for A. crenata alone. Amphibola is distinguished from the other amphibolids by a larger shell with a prominent square shoulder and raised, indented sinus. The operculum is unique within the Amphibolidae in its elongate shape and basal, rather than eccentric, nucleus. Other characteristic features include the highly folded spermoviduct and cylindrical spermovipositor containing a second, blind-ending duct of unknown function.