108 



BRITISH CRETACEOUS BRACHIOPODA. 



And as the stratum in question contains some twelve or more species of Brachiopoda, by 

 casting these into one or other deposit, the number of forms peculiar to each is necessarily 

 materially modified. This will in great measure explain why in my table only eight species 

 are recorded from the Lower Green Sand, while there would exist twenty-two, according to 

 Viscount D'Archiac and others. 



I mentioned in 1852 (page 2 of this Monograph), "that the age of the Farringdon 

 beds may yet afford a subject of discussion, although several geologists state them to be 

 Lower Green Sand?' Since then, Mr. Sharpe has renounced his share in the views enter- 

 tained by Messrs. Austen, Forbes, and others, 1 and has lately published a very interesting 

 memoir, 2 wherein he exposes his present opinion, which is chiefly founded upon the 

 examination of 111 species he had been able to assemble from that celebrated locality. 

 But as these results are not in accordance with those of other geologists, and differ like- 

 wise with my own, I will endeavour in a few short observations to explain wherein we 

 disagree. 



Mr. Sharpe records his palseontological inferences in the following table : 





bo 



a 



o 



CL, 



</2 



O 

 N 

 O 

 >> 



pS 



O 

 CL, 

 O 



13 



a 

 u 

 cq 



i * 



.J 2 



.0 



U 



■Si 



a <s 



'0 

 C 

 t/2 



la 



H 



Species peculiar to the deposit 



4 



1 



1? 



3 



4 



1 



14 



Maestricht Sands ...... 



2 



3 



4 



3 



- 



- 



12 



Upper Chalk ...... 



1 



20 



3 



5 



- 



3 



32 



Lower Chalk ...... 



1? 



2 



3 



2 



- 



4 



12 



Upper Green Sand, including Tourtia 



11 



17 



11 



- 



- 



3 



50 



Gault 



— 



1 



1? 



2 



- 



1 



5 



Lower Green Sand 3 ..... 



— 



4 



2 



3 



3 



1 



13 



Total number of Species examined . 



16 



44 



19 



18 



7 



7 



111 



1 Quarterly Journal of the Geol. Soc, vol. vi, p. 454, 1850. 



2 lb., yoI. x, p. 176, Nov., 1853. 



3 Mr. Sharpe mentions the following Lower Green Sand species as occurring in the Farringdon 

 Gravels : 



" Reptomulticava micropora. 



,, collis, also found in the White Chalk. 



" Heteropora cryptopora, also found in the Maestricht Sand. 

 " Proboscina marginata. 

 " Terebraiula tamarindus. 



„ oblonga, also found in the Upper Green Sand. 



" Ostrea macroptera, also in the Gault and Upper Green Sand, and perhaps in the Chalk. 

 " Pecten Dutemplii, also in the Upper Green Sand. 

 " Pecten inter striatus, perhaps identical with P. Dutemplii. 

 " Serpula quinque-angulata. 



