121 



SUMMARTf. 



In the Pliocene strata of Britain 212 distinct species of Verte- 

 brata are known to occur ; about 20 of these have evidently been 

 derived from Eocene rocks, and several others have only been 

 generically determined, or the species is somewhat jincertain. 

 After the elimination of these derived and doubtful forms, how- 

 ever, about 142 definite species remain, and it is these only which 

 are made use of in the following summary, although there are 

 about 190 species which may be accepted as constituting the 

 Vertebrata fauna of the British Pliocene deposits as at present 

 known. 



The Nodule-bed below the Coralline Crag has rarely been 

 exposed, and consequently has yielded but few vertebrate remains ; 

 the specific determination of those which have been found is in 

 most cases uncertain, and the specimens themselves are not 

 accessible. 



The Nodule-bed below the Red Crag is the horizon which has 

 been worked for " Coprolites," and from it 68 species of verte- 

 brates have been obtained, six of which are now living, while 62 

 have become extinct. From the Coralline Crag itself only 15 

 species are known, five of which are living and 10 extinct. The 

 Red Crag, properly speaking, that is, excluding the Nodule-bed at 

 its base, has yielded very few Vertebrata, only six species being 

 known, and three of these are living forms. The Norwich Crag 

 has given us 21 vetebrate species, of which five are still living. 

 From the Weybourn Crag only seven species are known, and five 

 of these are now living. From the Forest-bed Series ' of deposits 

 65 species have been obtained, and 45 of them are still living. 



The following Table gives the above statistics in a more acces- 

 sible form, and at the same time indicates the proportion of the 

 species 'of Vertebrata which lived in earlier Pliocene times, as well 

 as the numbers of those which lived on to a later period, although 

 now extinct. 



