578 HISTORY OF GEOLOGY. 



majority, in another, a minority of existing species. 

 We are not to run into this incongruity, for we are 

 not so to apply the names. The formation which 

 has been called pleiocene, must continue to be so 

 called, even where the majority of recent species 

 fails; and all rocks that agree with that in date, 

 without further reference to the numerical relations 

 of their fossils, must also share in the name. 



To invent good names for these large divisions 

 of the series of strata is indeed extremely difficult. 

 The term Oolite is an instance in which a descrip- 

 tive word has become permanent in a case of this 

 kind; and, in imitation of it, Pcecilite (from TTOIK/AOS, 

 various,) has been proposed by Mr. Conybeare 5 as a 

 name for the group of strata inferior to the oolites, 

 of which the Variegated Sandstone (Bunter Sand- 

 stein, Gres Bigarre',) is a conspicuous member. For 

 the series of formations which lies immediately over 

 the rocks in which no organic remains are found, 

 the term Transition was long used, but with ex- 

 treme ambiguity and vagueness. When this series, 

 or rather the upper part of it, was well examined in 

 South Wales, where it consists of many well-marked 

 members, and may be probably taken as a type for 

 a large portion of the rest of the world, it became 

 necessary to give to the group thus explored a 

 name not necessarily leading to assumption or con- 

 troversy. Mr. Murchison selected the term Silu- 

 rian, borrowed from the former inhabitants of the 



5 Report, p. 379. 



