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Ericusa sowerbyi (Kiener, 1839) Description: Shell medium to heavy in weight; protoconch prominent, spire whorls slightly rounded. Body whorl weakly shouldered, slightly concave between suture and shoulder. Columella with three strong plaits. Outer lip thickened internally at posterior end, flared at anterior end. Background colour cream or pale tan, marked with wavy axial brown lines; pale band below suture. Interior pinkish cream. Size: Adults 88-285 mm in length. Distribution: Endemic to Australia; Cape Moreton, Queensland, to Kangaroo Is., SA, including Tasmania. Habitat: Known from 20-494 metres. Common. Synonymy: Shells from NSW were named Mesericusa sowerbyi perspecta Iredale, 1929 and differentiated as "being larger size, lengthened spire, narrower build and somewhat different coloration" to Tasmanian shells, but this subpecific separation is not warranted as these characters vary continuously within the species. Mesericusa stokesi Cotton, 1961 was applied to a pale, fawn shell from Beachport, South Australia, also within the range of variation of the species. A specimen with white interior, instead of the usual pinkish-cream was named Ericusa sowerbyi porcellana Jackson, 1954. Remarks: This species shows considerable variation in the size of adult shells. A small form 80-100 mm in length occurs commonly off Sydney, at a depth of about 120 metres. Larger shells, up to 200 mm in length, are occasionally taken in the same trawl as the small form, and it has been suggested that there is sexual dimorphism in size. The species occurs over a great depth range - from about 50 metres to 450 metres off Sydney - with shells from deeper water being heavier than those from shallow water. There is also a trend for shells to become heavier, smaller, and more ovate with increasing latitude, but many specimens are exceptions to this trend. Fig. 1 Trawled between Sydney and Wollongong (DLB1597) Fig. 2 SYNTYPES of Mesericusa sowerbyi perspecta Iredale, 1929 (C.057721) Fig. 3 HOLOTYPE of Ericusa sowerbyi porcellana Jackson, 1954 (C.103337) |
