Therasia thaisa Hutton, 1883

Brook, Fred J., Kennedy, Martyn, King, Tania M., Ridden, Johnathon, Shaw, Matthew D. & Spencer, Hamish G., 2020, Catalogue of New Zealand land, freshwater and estuarine molluscan taxa named by Frederick Wollaston Hutton between 1879 and 1904, Zootaxa 4865 (1), pp. 1-73 : 37-38

Therasia thaisa Hutton, 1883

Pl. 4, fig. G

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

Type material. Lectotype (designated here), CMNZ M12784 [ex M268], and paralectotypes (7), CMNZ M268 (dry shells). The molluscan collection at CMNZ has a shell, radula and jaw mounted on a glass slide with the label details ‘ Therasia thaisa , Southland, XVI p. 182’, in Hutton’s handwriting (i.e., CMNZ 2017.17.65–2017.17.66), which is probably primary type material (see descriptions of radula by Hutton 1884b: 182).

Label details. CMNZ M268—‘49. Therasia thaisa Hutton , Southland’, pillbox label in Hutton’s handwriting.

CMNZ molluscan catalogue details. M1045—‘ Therasia thaisa Hutton , Southland (old number ZS 690)’

Type locality. ‘Waiau, Southland (G. M. Thomson)’ ( Hutton 1883g: 477, 1884b: 183).

Previous illustrations of type material. Jaw and radula teeth illustrated by Hutton (1884b: pl. 9, fig. M, pl. 11, fig. T) probably from type material; Pilsbry (1892 [in 1893–1895]: 346, pl. 3, figs. 14–16—‘ Type. Suter, del.’).

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). Therasia thaisa Hutton is the type species of Therasia Hutton, 1883 , by subsequent designation of Pilsbry (1893 [in 1893–1895]: 15). Pilsbry had earlier (1892) nominated Nanina celinde Gray, 1850 as the type of Therasia , but this was invalid as the latter species was not in Hutton’s original list. There has been confusion over the identity and distribution of T. thaisa : it has variously been interpreted as having a wide distribution in New Zealand, from Auckland, in the North Island, to the southern South Island (e.g., Hutton 1884c: 202, Hedley & Suter 1893: 641, Suter 1894b: 247); or being present throughout the South Island and on Rakiura/Stewart Island, only (e.g., Suter 1913: 661, Powell 1979: 316). Preliminary results of a phylogenetic study, and examination of museum collections, indicate that the distribution of T. thaisa Hutton, 1883 is in fact restricted to the southern South Island, Rakiura and Whenua Hou/Codfish Island (M. Kennedy unpub. data).

Current taxonomy. Therasia thaisa Hutton, 1883 — Hutton (1884c: 202), Hedley & Suter, (1893: 641), Suter (1913: 660), Powell (1979: 316), Spencer et al. (2009: 216).

Distribution. New Zealand; southern South Island, Rakiura and nearshore islands, Whenua Hou (AIM and NMNZ collection records).