Therasia tamora Hutton 1883

Therasia tamora Hutton, 1883

Pl. 4, fig. E

Hutton, 1883. The New Zealand Journal of Science, 1: 477.

Type material. Lectotype (designated by Cumber 1967: 69), CMNZ M10283 [ex M260], and paralectotypes (3), CMNZ M260 (dry shells).

CMNZ molluscan catalogue details. M260—‘ Therasia tamora Hutton, Auckland (4 specimens) (old No. 48) ’.

Type locality. ‘ Auckland (T. F. Cheeseman)’ (Hutton 1883g: 477, Hutton 1884b: 182).

Previous illustrations of type material. Pilsbry (1892 [in 1892–1893]: 70, 303, pl. 22, figs. 49–51—‘from the type’, ‘H. Suter, del.’); Suter (1915: pl. 9, figs. 7, a, b—possibly the same shell as illustrated by Pilsbry); Cumber (1961: fig. 2 D–F).

Remarks. Hutton submitted a description of this species to the Transactions and Proceedings of the New Zealand Institute issue for 1883, but publication was delayed until May 1884 (Hutton 1884b: 182), and was preempted by a brief description in an account of a meeting of the Philosophical Institute of Canterbury (Hutton 1883g: 477). Powell (1948: 276) erected the genus Therasiella for T. tamora and two other species, noting that they differed from typical Therasia in having membranously plaited epidermal processes, and a smaller number of teeth in the radula. In a taxonomic review of Therasiella, Cumber (1967: 69) noted that tamora differed from other species in this genus in having “oblong, bluntly rounded extensions of the periostracal plaits together with the absence of any fine processes on these plaits”. These periostracal processes are commonly damaged or lost during life or subsequent preservation of shells, and although depicted in illustrations by Pilsbry (1892 [in 1892–1893]: pl. 22, figs. 49–51) and Suter (1915: pl. 9, figs. 7, a, b), they are absent from the three extant type specimens of T. tamora.

Current taxonomy. Therasiella tamora (Hutton, 1883) — Powell (1948: 276, 1957: 118, 1979: 312), Cumber (1967: 67), Spencer et al. (2009: 216).

Distribution. New Zealand; northern North Island and nearshore islands from Houhora south to Kawhia and Gisborne, and on Marotere/Chicken, Taranga/Hen and Hauturu/Little Barrier islands (Suter 1913: 660; Cumber 1967: 69, fig. 5E; Powell 1979: 312; AIM and NMNZ collection records).