Fig. 125.—Portion of the radula of Cassis sulcosa Born., × 40. The marginals to the right are not fully drawn.
(c) The Taenioglossa comprise 46 families in all, of which the most important are Tritonidae, Cassididae, Cypraeidae, Strombidae, Cerithiidae, Turritellidae, Melaniidae, Littorinidae, Rissoidae, Paludinidae, Ampullariidae, Cyclophoridae, Cyclostomatidae, and Naticidae. The radula is characterised by a central tooth of very variable form, the prevailing type being multicuspid, the central cusp the largest, on a rather broad base; a single lateral, which is often a broad plate, more or less cusped, and two uncini, rather narrow, with single hooks, or slightly cusped. The accompanying figures of Cassis, Vermetus, and Cypraea, and those of Littorina and Cyclophorus given on pp. [20, 21], are good examples of typical taenioglossate radulae.
Fig. 126.—Four rows of teeth from the radula of Vermetus grandis Gray, Andamans. × 40.
In Homalogyra the radula is much degraded, the central tooth is large and triangular on a broad base, the lateral is represented only by a thin oblong plate, and the uncini are absent. In some species of Jeffreysia the uncini are said to be absent, while present in others. Lamellaria has lost both its uncini, but the radula of the allied Velutina is quite typical. A peculiar feature in this group is the tendency of the marginals to increase in number. A stage in this direction is perhaps seen in Ovula, Pedicularia, and the Cyclostomatidae. Here the outermost of the two marginals is by far the larger and broader, and is strongly pectinated on its upper edge; in the Cyclostomatidae the pectinations are rather superficial; in Ovula (where both marginals are pectinated) they are decidedly deeper; in Pedicularia they are deeper still, and make long slits in the tooth, tending to subdivide it altogether. In Turritella the number of marginals is said to vary from none (in T. acicula) to three (T. triplicata), but the fact wants confirmation. Solarium is an aberrant form, possessing simply a number of long uncini, which recall those of Conus or Pleurotoma, and is therefore hard to classify; the allied Torinia has a radula which appears allied to Ovula or Pedicularia. In Triforis the teeth are identical throughout, very small, about 27 in a row, tricuspid on a square base, cusps short.
The normal formula of the Taenioglossa is 2.1.1.1.2; in Lamellaria, 1.1.1; in Triforis, 13.1.13, or thereabouts.
Fig. 127.—Two rows of the radula of Cypraea tigris L. × 30.
Fig. 128.—Portion of the radula of Ianthina communis Lam. × 40.