_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_). [Illustration: 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. _Onchidiidae_: Rows oblique at the centre, straight near the edges; central strong, tricuspid; laterals and marginals very long, falciform, arched, unicuspid. _Auriculidae_: Teeth very small; central narrow, tricuspid on rather a broad base; laterals and marginals obscurely tricuspid on a base like _Succinea_. _Limnaeidae_: Jaw composed of one upper and two lateral pieces; central and lateral teeth resembling those of Helicidae; marginals much pectinated and serriform (Fig. 141, A). In _Ancylus_ proper the teeth are of a very different type, base narrow, head rather blunt, with no sharp cusps, teeth similar throughout, except that the marginals become somewhat pectinated (Fig. 141, B); another type more resembles _Limnaea_. [Illustration: FIG. 141.--Portions of the radula of =A=, _Limnaea stagnalis_ L., with the central tooth and two first laterals, and two of the marginals, very highly, magnified; =B=, _Ancylus fluviatilis_ Müll., with two of the marginals very highly magnified; =C=, _Physa fontinalis_ L., with central tooth and two of the marginals very highly magnified.] _Physidae_: Jaw simple, but with a fibrous growth at its upper edge, which may represent an accessory plate; radula with very oblique rows, central tooth denticulate, laterals and marginals serriform, comb-like, with a wing-like appendage at the superior outer edge (Fig. 141, C). _Chilinidae_: Central tooth small, cusped on an excavated triangular base, marginals five-cusped, with a projection as in _Physa_, laterals comb-like, serrations not deep.