Helix dimorpha Reeve, 1852

Brook, Fred J. & Ablett, Jonathan D., 2019, Type material of land snails (Mollusca: Gastropoda) described from New Zealand by taxonomists in Europe and North America between 1830 and 1934, and the history of research on the New Zealand land snail fauna from 1824 to 1917, Zootaxa 4697 (1), pp. 1-117 : 41

Helix dimorpha Reeve, 1852

Pl. 4, fig. E

Reeve, (1851–1854) 1852. Conchologia iconica, 7: species 775, pl. 128, fig. 775.

Type material: Lectotype, NHMUK1962729 /1, and paralectotypes (2), NHMUK1962729 /2–3 (dry shell material); ex Museum Cuming (Acc. no. 1829) . Lectotype designated by Marshall & Barker (2007: 71).

Label details: ‘Dimorpha P.’—in Pfeiffer’s handwriting. ‘New Zealand’.

Type locality: ‘New Zealand’ (Reeve 1852 [in 1851–1854]: species 775).

Previous illustrations of type material: Reeve (1852 [in 1851–1854]: pl. 128, fig. 775); Tryon (1886 [from Reeve, 1852]: pl. 62, fig. 39).

Remarks: Helix dimorpha Reeve, 1852 and H. dimorpha Pfeiffer, 1853 are based on the same type material, which H. Cuming had obtained from the Australian-based naturalist Frederick Strange. Marshall & Barker (2008: 71, 72) noted that the type material at NHMUK contained two specimens of H. dimorpha , and one of Allodiscus conopeus Marshall & Barker, 2008 (= Allodiscus nematophora Reeve, 1854 —see entry for latter species below). These taxa have allopatric distributions in the North Island ( Marshall & Barker 2008), indicating that the type material came from more than one location. Pfeiffer evidently intended to publish the original description of H. dimorpha in the Proceedings of the Zoological Society of London issue for 1851 (see Reeve 1852 [in 1851–1854]: species 775; Pfeiffer 1853a: 68), but publication was delayed until 1854 ( Pfeiffer 1854b: 148), and was pre-empted by Reeve (1852 [in 1851–1854]). Helix dimorpha Reeve, 1852 [= Helix dimorpha Pfeiffer, 1853 ] was listed as the type species of Psyra Hutton, 1883 (non Walker, 1860) by Pilsbry (1892 [in 1892–1893]: 65), and of Allodiscus Pilsbry, 1892 (replacement name for Psyra Hutton), but incorrectly as the type species had been fixed by original designation of Hutton (1883c: 532) (see remarks under Helix venulata Pfeiffer ).

Current Taxonomy: Listed as Allodiscus dimorphus (Reeve, 1852) by Hedley & Suter (1893: 638), Suter (1913b: 639), Powell (1979: 319), Marshall & Barker (2008: 70) and Spencer et al. (2009: 215). Helix dimorpha Pfeiffer, 1853 is a junior primary homonym and an objective junior synonym.

Distribution: New Zealand; northern North Island ( Marshall & Barker 2008).