In the Bulimulidae, which include the important genera Placostylus, Amphidromus, Partula, Amphibulimus, and all the groups of South American Bulimulus, the jaw is very characteristic, being thin, arched, and denticulated at the edges, as if formed of numerous narrow folds overlapping one another. The radula is like that of the Helicidae, but the inner cusp of the laterals is usually lengthened and incurved. In Partula the separation between laterals and marginals is very strongly marked.
The remaining families of Pulmonata must be more briefly described. In the Cylindrellidae there are three distinct types of radula: (a) Central tooth a narrow plate, laterals all very curiously incurved with a blunt cusp, no marginals (Fig. [140], D); (b) radula long and narrow, central tooth as in (a), two laterals, and about eight small marginals; (c) much more helicidan in type, central and laterals obtusely unicuspid, marginals quite helicidan. Type (c) is restricted to Central America, types (a) and (b) are West Indian.
Pupidae: Radula long and narrow; teeth of the helicidan type, centrals and laterals tricuspid on a quadrate base, marginals very small, cusps irregular and evanescent. This type includes Anostoma, Odontostomus, Buliminus, Vertigo, Strophia, Holospira, Clausilia, and Balea.
Stenogyridae, including Achatina, Stenogyra, and all its sub-genera: Central tooth small and narrow, laterals much larger, tricuspid, central cusp long, marginals similar, but smaller.
Achatinellidae: Two types occur; (a) teeth in very oblique rows, central, laterals, and marginals all of the same type, base narrow, head rather broad, with numerous small denticles (Achatinella proper, with Auriculella and Tornatellina, Fig. [140], E); (b) central tooth small and narrow, laterals bicuspid, marginals as in Helix (Amastra and Carelia).
Fig. 140.—Portions of the radula of A, Hyalinia nitidula Drap., Yorkshire, with central tooth, first lateral, and a marginal very highly magnified; B, Helix pomatia L., Kent, showing central tooth, laterals, and one extreme marginal, the two former also highly magnified; C, Orthalicus undatus Brug., Trinidad, with three laterals highly magnified; D, Cylindrella rosea Pfr., Jamaica, central tooth and laterals, the same very highly magnified; E, Achatinella vulpina Fér., Oahu, central tooth (c) and laterals, the same highly magnified.
Succineidae: Central and laterals helicidan, bi- or tricuspid on a quadrate plate, marginals denticulate on a narrow base; jaw with an accessory oblong plate.
Janellidae: Central tooth very small, laterals and marginals like Achatinellidae (a).
Vaginulidae: Central, laterals, and marginals unicuspid throughout, on same plan.