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 Plcurofomaria and the Meso- 



Fig. i go. Hippurites Toucasiana. 

 A large individual, with two smaller 

 ones attached to it. Upper Cretace- 

 ous, South of Europe. 



Fig. -2.<x>. Valuta elongata. 

 White Chalk. 



zoic Nerintza, we meet with examples of such modern types 

 as Turritella and Natica, the Staircase-shells (Silarium], the 

 Wentle-traps (Scalaria), the Carrier-shells (P/wrus), &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 

 (Valuta, fig. 200), the Cowries (Cyprcea], the Mitre-shells 

 (Mitra), the Wing - shells (Strombus], the Scorpion - shells 

 (P.eroceras), &c. 



