Rectacirsa fregata

Description:

Dimensions range from 4 mm - 4 mm high and 1.5 mm wide.
Width to height ratio: 0.38:1 ~ 0.38:1

Shell: stout, ventricose; solid; minute. Exterior colour dirty white. About 9.5 whorls, well rounded, convex; protoconch elongate, slightly tilted, terminating in a vertex with ~3.5 whorls smooth; teleoconch with ~6 whorls. Suture deep. Imperforate: no umbilical chink. Approximately 11 costae on the body whorl. Costae are separated, elevated, do not continue onto the base. Intercostal spaces spirally straiate. Interstices with approximately 10 spiral striae per whorl. Base with a strong keel where the axial ribs terminate. Aperture roundly oval, lip with strong flattened varix.

Beechey [2008ah] commented that Rectacirsa fregata (Iredale, 1936) may be distinguished from Cylindriscala distincta (E. A. Smith, 1891) by its smaller, angled protoconch and microscopically pitted intritacalx. Additionally, R. fregata has 11 costae on the final whorl, whereas C. distincta has 16.

Distribution:

Sydney, New South Wales, Australia. Known form the holotype and one other specimen [Beechey, 2008].

Habitat:

continental shelf -deep water.

Etymology:

Unclear. If it is a Latin derivative, it may be from the Latin fregata (frigate), presumably referring to a frigate or frigate ship; the reason for the name was not explicitly stated by the author.

Type Material:

Holotype: AMS C.24412 for Rectacirsa fregata Iredale, 1936 - Type Locality: off Sydney, New South Wales, 250 fms [= 457 m]. [Brown & Neville, 2015: 74]