272 Coralline and Red Crag Species. 



chiata 151 species, of the Gasteropoda 160, and 1 Ptero- 

 pod, Cleodora infundibulum. Of the 316 species only 

 52 are said to be extinct, or about 1 6 per cent, or, in 

 other words, 84 per cent, are still living. Sixteen 

 species of Echinodermata are known, 6 of which still 

 live ; and fish are found identical with living species 

 of Cod, Pollack, and Whiting, together with large 

 teeth of a shark, Carcharodon megalodon, Otodus, 

 Raia antiqua, &c. It is quite possible that the Coral- 

 line Crag beds may be approximately of the same age 

 with the marine shell beds of the Faluns of Touraine, 

 in France, commonly called Miocene. 



The Red Crag is chiefly a ferruginous sand, often 

 crowded with shells entire and broken, very irregularly 

 bedded, in a manner which shows that it was deposited 

 partly in shallow seas, with strong tidal currents near 

 shore, and, indeed, was partly accumulated between the 

 high and low water lines. 



At Felixstow the Red Crag is well seen on the sea- 

 cliff, lying directly on the London Clay. It is crowded 

 with shells, many of them broken, and was evidently 

 deposited in shallow water. At Walton-on-the-Naze, 

 where it also lies on London Clay, the sea was deeper, 

 the shells being often unbroken, and in the state in 

 which they died. 



A hundred -and-forty species are common to the 

 Red and Coralline Crag. In 234 species of shells, 150 

 now live in British seas, while ' 32 are now restricted to 

 more southern and 23 to more northern seas ' (Prest- 

 wich). In all about 92 per cent, of the Mollusca are 

 said to be still living. In 25 species of corals, 14 still 

 inhabit our coasts. Among its characteristic shells are 

 Trophon antiquum (Fusus contrarius), and various 

 species of Murex, Valuta, Buccinum, Natica, Purpura, 



