200 TERTIARIES OF COS. 



same geological period with those of the valleys 

 of Xanthus and Cibyra. We have seen that 

 those Lycian fresh-water beds were of date pos- 

 terior to the meiocene marine formations of the 

 same region. Thus we get an ante-date ; and in 

 Cos we get a distinct after-date, for there the 

 same beds, or what were probably beds of the 

 same age, form the walls of a tertiary basin of 

 later date. This basin consists of a well-de- 

 fined series of marine deposits, containing nume- 

 rous newer pliocene fossils, identical with those of 

 Rhodes and of Sicily. The Cos fresh-water beds, 

 and those of Lycia, may therefore be regarded 

 as older pliocene at latest. 



The fossils in the newer pliocene marine 

 formation are extremely numerous, both as to 

 species and individuals. They consist of such 

 testacea as now live in the neighbouring sea, 

 mingled with others extinct, or known only as 

 inhabitants of the Red Sea and Indian Ocean. 

 Many species, too, now very rare in the neigh- 

 bouring seas, such as Nassa semistriata, and Sili- 

 quaria anguina> are abundant in the fossil state, 

 whilst others now plentiful in the iEgean, are very 

 scarce in the tertiaries. Such shells as the Phorus, 

 and the Niso, conspicuously represent the extinct 

 forms. 



