THE CRETACEOUS PERIOD. 



279 



and Egypt. Species of this family occur in such numbers in 

 certain compact marbles in the south of Europe, of the age of 

 the Upper Cretaceous (Lower Chalk), as to have given orgin 

 to the name of " Hippurite Limestones, " applied to these 

 strata. 



Fig. 199. Hippuritea Toucasiana. 

 A large individual, with two smaller 

 ones attached to it. Upper Cretace- 

 ous. South of Europe. 



Tig. 200. Valuta elongata. 

 White Chalk. 



The Univalves (Caster o pods') of the Cretaceous period are 

 not very numerous, nor particularly remarkable. Along with 

 species of the persistent genus Pleurotcmaria and the Meso- 

 zoic Nerinaa, we meet with examples of such modern types 

 as Turritella and Natica, the Staircase-shells (Solarium}, 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 



