Genus Assiminea (Leach) Fleming 1828.
(= Syncera Gray 1821, Med. Repos., p. 239. A nomen nudum, according to Thiele, 1927, p. 114.)
Type: (by subsequent designation, Gray 1847; for Assiminea). A. grayiana Leach = Nerita Syncera hepatica Gray 1821 (fide Gray 1857, p. 23 in Turton's British Shells).
Assiminea vulgaris (Webster).
1905. Rissoia vulgaris Webster. Trans. N.Z. Inst., vol. 37, p. 277.
1913. Rissoa (Setia) vulgaris (Webster). Suter, Man. N.Z. Moll., p. 216.
1913. Barleeia chrysomela Melv. and Stand. Iredale, Pro. Mal. Soc., vol. 10, p. 370.
1915. Notosetia vulgaris (Webster). Iredale, Trans. N.Z. Inst., vol. 47, p. 454.
1915. Assiminea nitida (not of Pease 1865). Oliver, Trans. N.Z. Inst., vol. 47, p. 522.
1924. Tatea hedleyi Brookes. Trans. N.Z. Inst., vol. 55, p. 153.
1926. Assiminea nitida (not of Pease 1865). Finlay, Trans. N.Z. Inst., vol. 57. p. 379.
The first reference of the New Zealand shells to their correct family was in Finlay (1926, p. 379), where on Iredale's authority our species was referred to the widely distributed Polynesian Assiminea nitida (Pease). Finlay also mentioned that this species has been recorded from the Kermadecs by Oliver.
The species nitida, however, is not an Assiminea, as has been demonstrated by Thiele (1927, p. 128), for the dentition and open umbilicus show that it belongs to the genus Paludinella.
The writer has examined the dentition of Rangitoto specimens, which are topotypes of Brookes's Tatea hedleyi, and it is almost inseparable from that of grayana, the English genotype (as figured by Thiele 1. c.), having the characteristic hinder denticles on the central tooth, and moreover the shell has the umbilicus closed, which is a characteristic feature of the genotype, but not of nitida, in which it is quite open. The open umbilicus in nitida was mentioned in Pease's original description, and this feature is clearly shown in specimens from Tonga in the Auckland Museum collection.
Furthermore, upon shell characters, Kermadec Island specimens are inseparable from New Zealand examples.
If Iredale's statement (l.c., 1913, p. 370) is correct, that the Loyalty Island Barleeia chrysomela, Melville and Standen (1896, J. Conch., vol. 8, p. 309), is identical with the Kermadec Island shells, then it may be necessary later to change the specific name of the New Zealand shell once more. However, in the absence of Loyalty Island specimens, and taking into account both the poor condition of the holotype (as mentioned by Iredale, l.c., p. 370) and the fact that Iredale misidentified the Kermadec specimens as nitida, the wisest course meanwhile is to select an available New Zealand name for the New Zealand shell. This name comes from an unexpected source, as was revealed by a comparison between Webster's holotype of Rissoia vulgaris and topotypes of Brooke's Tatea hedleyi, which proved to be identical. It is possible that the combination Assiminea vulgaris has been used before, but I have not succeeded in tracing any such combination, so Webster's name may be employed for the New Zealand and Kermadec Island Assiminea, the type locality for which becomes Waipipi, Manukau Harbour.
Dentition (Fig. 7): The dental formula of Assiminea vulgaris is 1 + 1 + 1 + 1 + 1 + 1 + 1. Central tooth with five cusps, and three denticles on each side, below. Inner lateral with six cusps and outer lateral with five. Marginal teeth with 15 pectinate cusps. The central tooth is a little broader, and the cusps more regular in size, otherwise the dentition of vulgaris is almost identical with that of the genotype.