﻿Yol. 66. J JURASSIC STRATA OF SOUTH DORSET. 53 



packing of specimens, and many have not been unpacked again. 

 As a consequence the identification of species must often be given 

 in general terms, as they were set out in the notes : to wait until 

 the specimens were brought together, freed of matrix, and exactly 

 identified, would lead to indefinite postponement. 



However, identification in general terms is sufficient at present, 

 because one does not ascertain the dates of the deposit so much 

 by the actual species, as by the general facies, in the case of 

 Ammonites. Coarse-ribbed Dumortierice, fine-ribbed Dumortierice, 

 Ammonites of aalensis pattern, Opalijioids, show the dates as well 

 as more exact identifications ; because the successive Ammonites 

 of different genera assume certain developmental facies. Examples 

 of how this may be a guidance will be given later. In some cases 

 there may be difficulty, and more exact identification is necessary : 

 especially in detailed division ; for instance, there are three or four 

 successive series of Opalinoids which are not easy to distinguish in 

 the rough, even in a general way, but their particular features are 

 noted in Table I (p. 55). 



(a) Bibliography of some of the Author's similar 

 communications. 



This paper is part of a series of communications made upon 

 similar subjects, mainly to this Society, but also to other scientific 

 bodies, so that a list of such prior communications is desirable. 



<1) 1889. 'Oa the Cotteswold, Midford, & Yeovil Sands, & the Division 



between Lias & Oolite' Quart. Journ. Geol. Soc. vol. xlv, 



pp. 440-73. 

 1 On the so-called " Upper Lias " Clay of Down Cliffs ' Quart. 



Journ. Geol. Soc. vol. xlvi, pp. 518-21. 

 'On the Jurense Zone' Journ. Northants. Nat. Hist. Soc. vol. vi, 



pp. 76-80. 

 1 The Ammonite Zones of Dorset & Somerset ' Rep. Brit. Assoc. 



(Cardiff) pp. 655-56 ; & Geol. Mag. dec. 3, vol. viii, pp. 502-04. 

 1 The Bajocian of the Sherborne District ; its Relation to Subjacent 



& Superjacent Strata' Quart. Journ. Geol. Soc. vol. xlix, 



pp. 479-521. 

 ' The Bajocian of the Mid -Cotteswold s ' Quart. Journ. Geol. Soc. 



vol. li, pp. 388-462, & pi. xiv. 

 ' Dundry Hill : its Upper Portion, or the Beds marked as Inferior 



Oolite (go) in the Maps of the Geological Survey' Quart. Journ. 



Geol. Soc. toI. lii, pp. 669-720. (In collaboration with the late 



Edward Wilson.) 



(8) 1897. 'Deposits of the Bajocian Age in the Northern Cotteswolds : the 



Cleeve Hill Plateau' Quart. Journ. Geol. Soc. vol. liii, pp. 607-29 

 & pi. xlvi. 



(9) 1898. ; On the Grouping of some Divisions of so-called "Jurassic" Time 



Quart. Journ. Geol. Soc. vol. liv, pp. 442-62. 



(2) 



1890. 



(3) 



1890. 



(4) 



1891. 



(5) 



1893. 



(6) 



1895. 



(7) 1896. 



