Fam. 1. Testacellidae.—Animal carnivorous, slug-like or spirally coiled, no jaw (whence the name Agnatha, often given to this group), radula with usually few, large, sickle-shaped teeth (p. [232]), shell variable, rarely absent, usually external. Cretaceous——. Principal genera: Chlamydephorus (shell a simple plate, internal), Apera, Testacella (slug-like, shell terminal), Strebelia, Streptostyla, Glandina, Salasiella, Petenia, Pseudosubulina, Streptostele, Tomostele, Streptaxis (Fig. [203]), Gibbus, Ennea, Daudebardia (Fig. [193]), Schizoglossa, Guesteria, Aerope, Paryphanta, Rhytida (subg. Diplomphalus, Elaea and Rhenea).
Fig. 294.—A, Ennea (Gibbulina) palanga Fér; A´ young of same; B, Gibbus lyonetianus Pall.
Fam. 2. Selenitidae.—Shell internal, external, or absent; jaw present, radula Testacellidan, central tooth present. Tertiary——. Genera: Selenites, Plutonia, Trigonochlamys, Pseudomilax (?), Rathouisia (?).
Fam. 3. Limacidae.—Shell present or absent, internal or external, spiral or not, tail often with a mucus pore, jaw (Fig. [107] A, p. 211) with projecting rostrum on cutting edge, radula with central tooth tricuspid, laterals bi- or uni-cuspid, marginals aculeate. Eocene——. Genera: Otoconcha, Urocyclus, Mariaella (subg. Tennentia), Parmarion, Helicarion, Cystopelta, Aspidelus, Estria, Vitrinopsis (subg. Vitrinoidea, Parmella), Damayantia, Nanina (= Ariophanta, including Pachystyla, Rhysota, Hemiplecta, Trochonanina, Euplecta, Orpiella, Xesta, Macrochlamys, Microcystis, Sitala, Kaliella, Durgella, Austenia, Girasia, Parmacochlea, Africarion, Sesara, Macroceras, and others), Vitriniconus, Parmacella, Limax (subg. Amalia and many sections), Vitrina (subg. Vitrinozonites, Velifera), Zonites (subg. Stenopus, Moreletia, Mesomphix, Hyalinia, Gastrodonta, Pristiloma, Poecilozonites, Thyrophorella).
Fam. 4. Philomycidae.—Shell absent, jaw limacidan, radula helicidan, shield covering all the body. Single genus, Philomycus (= Tebennophorus), with subg. Pallifera.
Fam. 5. Helicidae.—Shell present or absent, internal or external; jaw of various types, radula with central tooth tricuspid, equal in size to the first laterals, laterals bi- or tricuspid, marginals smaller, cusped. Eocene——. Principal genera: Oopelta (no shell), Arion (shell absent or formed of calcareous granules), Ariolimax, Geomalacus, Anadenus (subg. Prophysaon), Hemphillia, Cryptostracon, Binneya, Helix (see below), Cochlostyla, Bulimus (subg. Borus, Orphnus, Dryptus, Strophochilus, Pachyotus, and possibly Caryodes, Leucotaenia, Liparus, Livinhacea, Pachnodus, Rachis, Atopocochlis, Cerastus, Clavator belong here, or with Buliminus), Berendtia, Rhodea. Pilsbry proposes[408] to group Helix as follows:
A. Eggs or young very large at birth:
(1) Macroön, incl. Acavus, Pyrochilus (= Phania), Stylodonta, Helicophanta.
B. Eggs or young smaller or minute at birth: