RADULA OF THE TAENIOGLOSSA 



223 



until he was fortunate enough to discover that S. spectrtim, 

 unlike all other species of Sistrum, lives exclusively on a branch- 

 ing coral. 



The dental formula for the HacJtiglossa is thus 1.1.1, except 

 in those cases where the laterals are absent, when it is 0.1.0. 



(c) The Taenioglossa comprise 46 families in all, of which the 

 most important are Tritonidae, Cassididae, Cypraeidae, Strom- 

 bidae, Cerithiidae, Turritellidae, Melaniidae, Littorinidae, 

 Itissoidae, Paludinidae, Ampullariidae, (Jyclophoridae, Cyclostonia- 



FiG. 125. — Portion of the radiila of Cassis sulcosa Born., x 40. Tlie marginals 

 to the right ai'e not fully drawn. 



tidae, and JSTaticidae. The radula is characterised by a central 

 tooth of very variable form, the prevailing type being multi- 

 cuspid, the central cusp the largest, on a rather l)road base ; a 

 single lateral, whicli is often a broad plate, more or less cusped, 

 and two uncini, rather narrow, with single hooks, or slightly 



Fig. 126. — Four rows of teeth 

 from the radula nf Vcrmetus 

 grandis Graj', Audamaus. 

 x40. 



cusped. The accompanying figures of Cassis, Vermctus, and 

 Cypraca, and those of Littorina and Cydopliorvs given on pp. 

 20, 21, are good examples of typical taenioglossate radulae. 



In Hoiiialogyra the radula is much degraded, the central 

 tooth is large and triangular on a Ijroad base, the lateral is 

 represented only liy a tliin oblong plate, and the uncini are 

 al)sent. In some species of Jcffreysia the uncini are said to be 

 absent, while present in others. Lamellaria has lost l)oth its 

 uncini, l)ut the radula of the allied Velutina is quite typical. A 

 peculiar feature in this group is the tendency of the nuirginals 

 to increase in number. A stage in this direction is perhaps seen 



