REVISION OF THE GENUS ACAVUS FROM SRI LANKA (GASTROPODA: ACAVIDAE)

The genus Acavus from Sri Lanka includes three species, Acavushaemastoma (Linnaeus), Acavus superbus (L. Pfeiffer) and Acavusphoenix (L. Pfeiffer) with two subspecies, Acavus phoenix phoenix(L. Pfeiffer) and Acavus phoenix castaneus new subspecies.The conchological and anatomical differences between these species,as well as their intraspecific variation are described. Theirdistribution is shown on maps and all locality records are listed.The presence of extensive intraspecific polymorphism, the developmentof geographical subspecies and the presumable hybridizationbetween some species show that the Acavus species are not isolatedrelict species, but that speciation is in progress and thatthe radiation of the Acavus species is probably much youngerthan the radiation of the acavid genera. The three Acavus speciesare not acutely endangered at present. In contrast to manyother land snails, there is no risk of a rapid decline of theAcavus species due to deforestation, because these species alsooccur in synanthropic habitats. (Received 22 December 1998; accepted 2 October 1999)     

Additive typogenesis in Thoanteus (Gastropoda: Bulminidae)

Thoanteus ferrarii sp. nov. from Crimea is described. The phylogeny of Thoanteus is reconstructed in a cladistic analysis and the evolution of this genus is discussed. Thoanteus ferrarii sp. nov. represents an early stage in the additive typogenesis of Thoanteus , in which the appendix retractor still inserts laterally at the appendix section A₁, a short distance from its proximal top, as in the Peristoma-like stem species of Thoanteus.