CAINOZOIC FAUNAS 207 



characteristic Pliocene species was sinistral, while 

 modern types are normally dextral. Spinous Muricidae 

 are hardly less abundant; Typhis, with small shells 

 ornamented by hollow excrescences, being especially 

 common in the Barton Clay. Purpura (Thais) is 

 abundant in the Pliocene, as at present. The Fusidae 

 are one of the most familiar Cainozoic families. Fusus 

 is common in the Eocene, and is there associated with 

 gerontic side-lines such as Sycum and Clavella. The 

 Barton Clay is particularly famed for its abundant 

 Volutidae ; scores of exquisite forms of Volutilithes 

 (PI. xvi. fig. 7) occur, together with the less ornate 

 species of Lyria. Maculopeplum is a well-known 

 Pliocene genus. The chief families of Toxoglossa are 

 the Turritidae and Conidae. Turris (Pleurotoma, PI. xvi. 

 fig. 8), divided into numerous sub-genera, is common 

 throughout the Eocene ; Conus> while enjoying its acme 

 at the present day, is well represented by less involute 

 forms (Conorbis) in the Eocene. 



Curiously enrolled types, such as Bullaria and 

 Seraphs, are familiar Tertiary members of the Tecti- 

 branch Euthyneura, but it is in the Pulmonate section 

 that the subclass finds its fullest Cainozoic expression. 

 Limnaea(f\. xvi. fig. 9) and Planorbis (PL xvi. fig. 10), 

 represented by species closely resembling modern types, 

 are largely responsible for the Bembridge Limestone, and 

 occur abundantly in other fresh-water Oligocene strata, 

 especially the Headon Beds. Snails are usually scarce 

 as fossils, but Helix (sens, lat.) and Amphidromus are 

 not uncommon in the Bembridge Beds. The degenerate 

 shells of Slugs are occasionally found in the same 

 deposit. 



Cainozoic Cephalopoda call for little palaeontological 

 comment. Nautiloids are almost restricted to the family 

 Nautilidae, one species of Nautilus still surviving. Large 



