THE CRETACEOUS PERIOD. 



271 



The Univalves {Gasteropods) of the Cretaceous period are 

 not very numerous, nor particularly remarkable. Along with 

 species of the persistent genus Pleurotomaria and the Meso- 



Fig. 199. — Hippurites Toucasiana. 

 A large individual, with two smaller 

 ones attached to it. Upper Cretace- 

 ous, South of Europe. 



Fig. 200. — Vohita elongata. 

 White Chalk. 



zoic Nerincsa, we meet with examples of such modern types 

 as Turritella and NatiCa, the Staircase-shells {Solariufn)^ the 

 Wentle-traps {Scalaria), the Carrier-shells {Phorus), &c. To- 

 wards the close of the Cretaceous period, and especially in 

 such transitional strata as the Maestricht beds, the Faxoe 

 Limestone, and the Pisolitic Limestone of France, we meet 

 with a number of carnivorous (" siphonostomatous ") Uni- 

 valves, in which the mouth of the shell is notched or pro- 

 duced into a canal. Amongst these it is interesting to 

 recognise examples of such existing genera as the Volutes 

 (Voluta, fig. 200), the Cowries {Cyprcea), the Mitre-shells 

 [Mitra), the Wing - shells {Strombus), the Scorpion - shells 

 (Fieroceras), &:c. 



