Observations on the Genus Aclisina, De Koninck, with Descriptions of British Species and of some other Carboniferous Gasteropoda

Abstract

In 1881 De Koninck, in his ‘Faune Calc. Carb. Belg.’ Ann. Mus. Roy. Hist. Nat. Belg. vol. vi, pt. iii, p. 86, created the genus Aclisina to include some small shells which had previously been placed in one or other of the genera Murchisonia, Loxonema, Aclis, Turbonilla or Turritella , and he thus defines it: ‘Petite coquille allongée, conique, à tours convexes, striés en spirale; ouverture ovale; bord externe mince, entier et non saillant: columelle non arquée, légèrement épaissie; axe non perforé.’ Three species are described as belonging to this genus, but none is especially regarded as the type. I have examined the shells labelled as the types in the Brussels Museum, and find that they are severally quite distinct from one another in character, so much so, indeed, that each must form the type of a separate genus. It remains, therefore, to be decided which should be regarded as most typical of De Koninck's definition of Aclisina . The first-mentioned, Murchisonia striatula , was referred by De Koninck in a former work to the genus Murchisonia , but he here removes it to Aclisina , because he states there is no slit (‘fente’) in the outer lip. The surface of the specimen from Vis6 in the Brussels Museum, marked as the type of this species, is much worn, but it is sufficiently preserved to prove its identity with other individuals from the same locality in the Brussels Museum, in the Museum and in the Collection of M. Destinez at Liége, and also with two