484 



MESOZOIC TIxME — REPTILIAN AGE. 



Crassatclla, Cyprina, Cytherea, Venus, Lucina, Panopsea, Avicula, Pecten, Neithea, 

 Pholas, Spondylus, Tellina, Plicatula, and many other genera of existing seas- 

 Figs. 782-785. 



Conchifers, Rudistes Family. — Fig. 782, Hippurites Toucasianus ; 782 a, H. dilatatus; 783, 

 Radiolites Bournoui; 784, Spherulites Hoeningshausi. Gasteropods. — 785, Nerinaea bisul- 

 cata; 785 A, Avellana Cassis. 



which give a modern aspect to a conchological cabinet of the Cretaceous period. 

 The genera Crassatella and Neithea commence with the Chalk. Among the spe- 

 cies of the extinct tribe of Rudistes, fig. 782, Hipjmrites Toucasianus, from the 

 Upper Cretaceous, one of the most common species of southern Europe; fig. 

 782 a, H. dilatatus, vertical view, showing the interior of the lower conical valve, 

 from the Lower Cretaceous ; fig. 783, Radiolites Bournoni, upper valve in profile, 

 from the Upper Chalk; fig. 784, Spherulites Hoeningshausi, upper valve in pro- 

 file, from the Upper Chalk ; h, c, in 783, 784, attachments of muscles. 



(d.) Gasterojjods. — The extinct genera Nerineea, Actseonina, Act&onella, Avel- 

 lana, etc. The modern genera Strombus, Busycon, Buccinum, Fusus, Vo- 

 LUTA, Oliva, Fasciolaria, Ovula, Cypr^a, Trochus, Ncrita, Natica, Mitra, 

 Conus, Cerithium, Bulla, etc., showing a striking approximation to the present 

 age in the closing period of the Mesozoic. (The genera in small capitals are 

 some of those which make their first appearance in the Cretaceous period.) 

 Fig. 785, Nerineea bisulcata d'Archiac, from the White Chalk. Fig. 785 A, Avel- 

 lana Cassis, from the Upper Green-sand ; a, outline sketch, showing the toothed 

 aj^erture. 



