MESGZOIC TIME — CRETACEOUS. 



861 



iar Eudistes, of which there are over a hundred species in the Cretaceous, 

 and none later; they are especially common in the Mediterranean region. 



1450-1455. 







14 )i 



1i54 



Lamellibranchs, JRudistes Family. — Fig. 1450, Hippurites Toucasianus ; 1451, H. dilatatus ; 1452, Eadiolites 

 Bournonl ; 1453, Sphaerulites Hceninghausi. Gastropods. — 1454, Nerinea bisulcata ; 1455, Cinulia aveUana. 



1456, 1457. 



1457 



Pig. 1450 represents Hippurites Toucasianus d'Orb. (with a small one 

 attached), and 1451, the interior of the shell of H. dilatatus. Figs. 1452, 

 1453 show the forms of the upper 

 valves, in profile, of species of 

 Radiolites and Sphceridites, of the 

 same family. The prominences 

 b, c are for the attachments of 

 muscles. A single species, Radio- 

 lites Mortoni Woodw., has been 

 found in England. Figs. 1454, 



1455, are Gastropods of the pecul- 

 iar genera Nerinea and Cinulia, 

 both now extinct. 



Two of the fresh-water shells from the Wealden are represented in Figs. 



1456, 1457, one a Unio, and the other the common Viviparus. 

 Ammonites were in great numbers ; and, as in America, the open-coiled 



forms are far more abundant than in the Jurassic. Several of the latter are 

 shown in Figs. 1458-1461, and a spiral form, Turrilites, in 1462. Another 

 related form is that of the open-coiled Turrilite, Helicoceras, which has 

 several species in Europe, as well as in America. Nautilus also has many 



Fig. 1456, Unio Valdensis ; 145T, Viviparus (Paludina) flu- 

 •riorum. 



