404 



Mr. J. Lycett on Fossil Shells from the 



somewhat diminished at Stroud, 

 and loses the greater portion of •:| 

 its volume, including the Oolite w 

 marl and all the upper beds before 

 it reaches Bath, where it is repre- 

 sented by 60 feet of freestone. The 

 Bath section is taken from a va- 

 luable paper by Mr. Lonsdale in 

 the Geological Transactions. The 

 shells of the middle division are 

 for the most part distributed in 

 beds of no great thickness ; the 

 great mass of the deposit being 

 nearly destitute of organic remains, 

 or containing only minute shelly 

 detritus. 



The numerical results obtained 

 from the Tables of comparison are 

 as follow: — 255 species have been 

 examined from the middle division 

 of the Inferior Oolite, 181 being 

 from Leckhampton, and 145 from 

 Minchinhampton ; of these 73 are 

 common to the two localities and 

 64 pass upwards into the Great 

 Oolite, or 28 per cent. Of the '^ 

 Leckhampton shells alone 59, i. e. is 

 33 per cent., and of the Minchin- 

 hampton Inferior Oolite suite 43, 

 i. e. 31 per cent., pass upwards. 

 Thus, from each of the localities, a 

 larger per-centage of shells pass 

 upwards than is obtained when 

 the entire number of species are 

 reckoned ; an instance of the cau- 

 tious reliance which should be 

 placed upon estimates derived from 

 a limited number of species or 

 from shells of a single locality, 

 where the object is to draw wide 

 and general inferences. It should 

 also be stated that about 40 spe- . 

 cies in addition to these were not | 

 sufficiently perfect to be deter- "a 

 mined, nearly or quite the whole -^ 

 of which are unknown to the Great q 



