Thalassia propinqua Hutton, 1882

Pl. 4, fig. C

Hutton, 1882. New Zealand Journal of Science, 1: 281.

Type material. Lectotype (designated here), CMNZ M168.4, and paralectotypes, CMNZ M168.1–3 (3) and CMNZ M12772 [ex M168] (1) (dry shells). The molluscan collection at CMNZ has a radula and jaw mounted on a glass slide with the label details ‘ Thalassia propinqua, Weka Pass, XVI p. 169’, in Hutton’s handwriting (i.e., CMNZ 2017.17.83), which is probably primary type material (see description of radula by Hutton 1883d: 137).

Label details. M168—‘65. Thalassia propinqua Hutton, Weka Pass, Canterbury’, pillbox label in Hutton’s handwriting.

Type locality. ‘Weka Pass (C. Chilton)’ (Hutton 1882p: 281, 1883d: 137).

Previous illustrations of type material. Pilsbry (1892 [in 1892–1893]: 72, 304, pl. 22, figs. 55–57—‘drawn from the type, ‘H. Suter, del.’), Suter (1915: pl. 9, figs. 1, a—same shell as illustrated by Pilsbry).

Remarks. Hutton submitted a description of Thalassia (?) propinqua to the Transactions and Proceedings of the New Zealand Institute issue for 1882, but publication was delayed until May 1883 (Hutton 1883d: 137), and was pre-empted by a brief description in an account of a meeting of the Philosophical Institute of Canterbury (Hutton 1882p: 281). A description by Hutton (1884b: 169, pl. 10, fig. G, pl. 11, fig. V) of a jaw and radula purported to be from propinqua was based on a specimen from Southland collected by G. M. Thomson (i.e., CMNZ 2017.17.82) that is not type material of, or conspecific with, Thalassia propinqua Hutton, 1882. From Pilsbry (1892 [in 1892– 1893]: 72) onwards propinqua has generally been assigned to Thalassohelix Pilsbry, 1892 at subgenus or genus level, and it has been interpreted as having a wide distribution in New Zealand, between Auckland in the North Island, and the southern South Island (e.g., Hutton 1884c: 203, Hedley & Suter 1893: 636, Suter 1913: 631, Powell 1979: 318). However, preliminary results of a phylogenetic study indicate that propinqua belongs in genus Therasia Hutton, 1883; the genetic data and examination of museum collections indicate that it has a distribution spanning the south-eastern North Island and north-eastern South Island, only (M. Kennedy unpub. data).

Taxonomy. Here treated as Therasia propinqua (Hutton, 1882) n. comb.

Distribution. New Zealand; south-eastern North Island from East Cape to Cape Palliser; Marlborough and Canterbury in the South Island (AIM and NMNZ collection records).