Helix chimmoi Pfeiffer, 1857

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 : 31-32

Helix chimmoi Pfeiffer, 1857

Pl. 3, fig. C

Pfeiffer, 1857. Proceedings of the Zoological Society of London, 24: 328.

Type material: Lectotype (here designated), NHMUK 1962709 /1; paralectotypes, NHMUK 1962709 /2-5 (4), NHMUK 20170010 (2) (dry shell material); ex Museum Cuming (Acc. no. 1829).

Label details: NHMUK 1962709/1-5, ‘ Helix Chimmoi Pfr, Sunday Is. Kermedec’—in Pfeiffer’s handwriting; ‘ Charopa , not fr. Kermadecs, T.I.’—in Tom Iredale’s handwriting; NHMUK 20170010, ‘ Helix Chimmoi Pfr, Sunday Islands’—in Pfeiffer’s handwriting.

Type locality: ‘ Sunday [= Raoul] Island, Kermandec (sic) Group (Lieut. Chimmo, R.N.)’ ( Pfeiffer 1857a: 328) .

Remarks: This species was described from material in the Cuming collection that had been obtained from William Chimmo. As noted in the introduction, Chimmo accompanied H.M.S. Herald on the first part of a hydrographic survey of the southwest Pacific in the early 1850s. The Herald visited Raoul Island in 1854, but Chimmo was not aboard at the time, and presumably obtained the type material of Helix chimmoi from the ship’s naturalists, John MacGillivray, William Milne, or one of the officers or crew of the Herald. Our examination indicates that the two lots in the NHMUK collection that were identified as H. chimmoi by Pfeiffer (i.e., 1962709, 20170010), and which are regarded here as primary type material, contain two species. We interpret the specimens in NHMUK 1962709/1- 5 as matching Pfeiffer’s description of H. chimmoi and designate 1962709/1 as the lectotype of this species. Other material of typical H. chimmoi that was collected on Raoul Island in 1854 by John MacGillivray was sent to the British Museum (NHMUK 1855.11.19.64), and is regarded here as a topotype lot. Sometime later, in the 1860s or early 1870s, further material of H. chimmoi was obtained from the Kermadec Islands by Dr. Edouard Graeffe, sent to the Museum Goddefroy, Hamburg, and redescribed by Mousson (1873) as Patula modicella var. vicinalis . The latter name is here treated as a junior synonym of H. chimmoi (see entry for P. modicella var. vicinalis , below). Tom Iredale carried out an extensive survey of the land snail fauna of Raoul Island in 1908, the results of which were reported on by Iredale (1913). He had examined the collection at the British Museum, and noted ( Iredale 1913: 384) that “I have ……found specimens which bear the label H. Chimmoi , and which someone has marked ‘Type”, and which agree with the Pfeifferian description. I have carefully examined them and would now suggest that the locality is quite erroneous. They are quite unlike anything I have collected, and though I do not claim to have absolutely obtained every mollusc, I cannot think that such a large and conspicuous form should have escaped me. My suspicions seem further confirmed in that two species about the same size were contained in this typical lot, and the other one is also quite unrepresented in my collection and is quite as unfamiliar as the typical H. chimmoi ”. Similarly, in comments on Patula modicella var. vicinalis, Iredale (1913: 384) noted that “Here, again, nothing agreeing with this description [i.e., by Mousson, 1873: 112] was found”. His comments indicate that he did not realise that H. chimmoi and Patula modicella var. vicinalis are conspecific. Oliver (1915: 565) followed Iredale in concluding that these two taxa were mislocalised, and not part of the Kermadec Islands fauna. However, it is very unlikely that the specimens obtained by Chimmo, MacGillivray and Graeffe, respectively, were all mislocalised. Rather, it is more probable that this species was present on Raoul Island up until at least the mid 1800s, but became extinct there sometime before Iredale’s visit to the island in 1908. Helix chimmoi is here assigned to the genus Charopa [Albers MS.] Martens, 1860 (family Charopidae ). The shells in NHMUK 1962709 and 1855.11.19.64 are very similar in shape, size and protoconch details to the New Zealand species Charopa montivaga Suter, 1894 , but differ in having more closely spaced radial ribs. The two paralectotypes in NHMUK 20170010 differ from typical H. chimmoi in having a taller spire and more widely-spaced ribs. They also appear to belong in genus Charopa , and if the locality details are correct, represent a previously unrecognised endemic species from the Kermadec Islands that is probably also now extinct.

Taxonomy: Treated here as Charopa chimmoi (Pfeiffer, 1857) n. comb.

Distribution: Kermadec Islands; Raoul Island ( Pfeiffer 1857a).