50 C.C. NATURAL HISTORY SOCIETY. 



The series enclosed within square lines are those which it was 

 not possible to bring into the special arrangement. 



The Stratigraphical Terms. 



A little explanation is perhaps required as regards the use of 

 the stratigraphical terms. Just as there are differences of opinion 

 as to the precise years of a man's life comprehended in the terms 

 ' youth,' ' maturity ' and ' old age,' so there are individual differences 

 of opinion as to the particular rocks to be denoted Lower, Middle, 

 or Upper Lias, and so forth. It becomes necessary then to state, 

 in certain cases, what meaning has been attached to particular 

 terms. Thus to the Middle Lias, following certain well-known author- 

 ities, has been given a wider significance than Marlstone : it has been 

 intended to include some of the clay beds immediately below, where- 

 fore the fossils from the brickyards of Cheltenham and Battledown 

 will be found inserted as Middle Lias. But such a matter of 

 naming does not affect their position in the case, which is designed 

 to represent actual relative position in the rocks irrespective of any 

 detail of nomenclature. 



Then in regard to the respective limits of Upper Lias and 

 Inferior Oolite, it has been deemed advisable to follow the recom- 

 mendation of the International Geological Congress, though the 

 division so made seems peculiarly arbitrary for this district. 

 Thus the Cotteswolds to the south of Stroud shew a few feei of 

 rock particularly rich in Cephalopoda ; known in consequence 

 as the Cephalopod Bed. But the adopted line divides the 

 lower part of this bed from the upper, placing the former to 

 the Upper Lias, and the latter to the Inferior Oolite. Wherefore 

 certain of the labels read thus, " Cephalopod Bed, Upper Lias," 

 and others, " Cephalopod Bed, Inferior Oolite." 



The Great Oolite Series as a major division should include 

 the rocks from the Fullers' Earth to the Cornbrash. It has not 

 been possible to keep the fossils from these different sub-divisions 

 always in their true line. The reason will be seen by an inspection 

 of the case. The bulk of the specimens come from the strata of 

 Minchinhampton often known for distinction as " Great Oolite, 

 proper," a sub-division of the whole Great Oolite Series. And 

 these fossils take up what may be said to be more than their share 

 of space. But this is a detail of the arrangement which may be 

 easily understood. 



