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Plastiscala morchi (Angas, 1871)

Description: Shell tall and slender, of up to 8½ teleoconch whorls. Protoconch of 1½ smooth, inflated whorls. Teleoconch whorls convex, with 2 varices per whorl, sculptured with low, rounded axial ribs. Ribs about 25 on second-last whorl, crossed by about 10 spiral cords; relative strength of axial and spiral sculpture variable, surface sometimes cancellate. Weak spiral cord level with top of aperture, terminating axial ribs. Base with several weaker cords. Aperture oval; outer lip thickened by varix externally. Umbilicus closed. Colour fawn.

Size: Up to 13 mm in length.

Distribution: Australia and Japan. In Australia, Manning River, NSW, southwards to Spencer Gulf, SA. In Japan, off Imazato Amami O-shima Island, Ryukyu Islands, in 200 m (Nakayama, 2003).

Habitat: Known from beach washup, and down to 457 m. Rare.

Comparison: Compared with P. magna, this species is more elongate, has more rounded whorls with stronger sculpture, and has stronger varices which are more regularly spaced. P. magna has no basal rib, but there is a weak rib in P. morchi.

Remarks: Two subspecies have been described. Plastiscala morchi bentha Iredale, 1936 (Fig. 2, HOLOTYPE) was described as "a larger, more slender shell with more rounded whorls. … the longitudinals are more sharply cut and the spiral cords are finer and more distinct". Plastiscala morchi profundior Iredale, 1936 (Fig. 3, HOLOTYPE) was differentiated by "the sculpture is much weaker, the longitudinal ribs notably so, while the concentric cording is also much less defined and the varices more flattened".

Fig. 1: Off Lakes Entrance, Victoria, 27-37 m (C.461137)

Fig. 2: HOLOTYPE of Plastiscala morchi bentha. 3.5-4 miles off Wattamolla, NSW, 99-108 m (C.016342)

Fig.3:  HOLOTYPE of Plastiscala morchi profundior 23 miles east of South Head, Sydney, 457 m (C.024420)


Copyright Des Beechey 2008