Vol. 51.] OF THE MID-C0TTESW0LDS. 391 



Conformable Strata. — When the sequence is complete. 

 Non-sequential Strata. — When the sequence is incomplete, 



but the planes of the deposits are practically parallel. 

 Unconformable Strata. — When the sequence is incomplete, 



and the planes of the deposits are not parallel. 



Part I. 



The Deposits of Bajocian Age from near Stroud to 

 Leckhampton Hill. 



In my former paper I mentioned that there had obviously been 

 confusion between the Gryphite- and Lower Trigonia-grits l ; that 

 in the Stroud area what was really the latter had been mistaken 

 for the former. As it is an important matter, in local as well as in 

 more extended correlation, that the names for two non- contempo- 

 raneous deposits should not be used indiscriminately or employed 

 the one for the other in different localities, one of the objects of 

 this part of the present paper is to show the development of the 

 different deposits. 



If the deposits were always present no difficulty would have been 

 experienced ; but it has long been recognized that in the Stroud 

 neighbourhood some of the ' intervening beds ' were absent, and it 

 has usually been taught that the Lower Trigonia-grit was the 

 missing member. Thus Wright, 2 in dealing with Rodborough Hill, 

 near Stroud, places 2 feet 6 inches of the 'intervening beds' as 

 Gryphite -grit, and only 1 foot as Lower Trigonia-grit ; but even 

 this allowance to the latter is dissented from by Lycett in a note 

 published by Wright in the same paper. Lycett 3 himself had, two 

 years previously, stated that ' in the Southern Cotteswolds the 

 series D [beds below the Gryphite-grit, namely the Lower Trigonia- 

 grit] seems to have thinned out altogether,' and further (op. cit. 

 p. 62) that there was ' a pause in the marine deposits during which 

 a series of beds, 24 feet thick, were accumulated in the Northern 

 Cotteswolds.' Lastly, Witchell 4 gives, in his general section of the 

 vicinity of Stroud, the Gryphite-grit as the only one of the ' inter- 

 vening beds,' varying from \\ to 12 feet in thickness. On p. 57 he 

 says that the Lower Trigonia-grit does not occur in the Stroud 

 neighbourhood, except possibly at Stroud Hill ; on p. 58, that in the 

 deposition in the Stroud area, as compared with Cleeve, there must 

 have been a considerable pause, as about 27 feet of strata are seen 

 at the latter place and not at the former. 



These statements of Witchell and Lycett in regard to the amount 

 missing are rather curious errors, seeing that the Lower Trigonia- 

 grit, ' the missing member,' is only about 7 feet thick. They cannot 

 have been based upon personal observation. Lycett's ' 24 feet ' is 



1 Quart. Journ. Geol. Soc. vol.xlix. (1893) p. 511. 



2 ' Subdivisions of Inf. Ool. in S. Engl.,' Quart. Journ. Geol. Soc. vol. xvi. 

 (1860) p. 44. 



3 ' Cotteswolcl Hills,' London & Stroud, 1857, p. 60. 

 - 1 ' Geology of Stroud,' 1882, p. 38. 



