Size and distribution of Archachatina ustulata, a South African achatinid land snail, with the description of a new subspecies

Archachatina (Tholachatina) ustulata (Lamarck, 1822), a species of the Afrotropical endemic pulmonate gastropod family Achatinidae, is a fairly well known taxon, restricted to the southeastern parts of South Africa. Connolly (1939: 302-303, pl. X fig. 3) has covered its nomenclatorial history and given a good description and figure of the shell. Mermod (1951: 746, fig. 90) has discussed and figured the holotype shell. Both these authors have used the name Achatina ustulata. Bequaert (1950: 202) and Van Bruggen (1965: 80) have merely listed the species under its now correct name, while Van Bruggen (1967: 22-24, fig. 10) has reviewed the distribution and dimensions of the shell in addition to supplying a first description and figure of the genital anatomy. Therefore this achatinid was considered seemingly well-known. However, a sample recently acquired by the Musée Royal de l’Afrique Centrale, Tervuren (Belgium; abbreviation MRAC) and in 1981 recognized as belonging to the above species by Prof. A. R. Mead, adds new data of considerable interest. This material was collected far beyond what was considered the range of the species and the shells appear to be aberrant in size. For reasons given below the new material is considered to represent a new subspecies. The nominate form and the new subspecies may be distinguished as follows: Shell length 53-85 mm, 6¼-7 whorls, coastal southeastern Cape Province from ca. 21°30’E to ca. 24°E ............................ A. ustulata ustulata Shell length 87-120 mm, 7¾-8¼ whorls, Pondoland ........ A. ustulata limitanea