ordovician brachiopoda 23 



Table ii 



The number of pedicle or brachial valves of the listed species 

 recovered from 4 localities of Whittery Shales 



1234 



Bicuspina subquadrata 2 1 17 15 



Caeroplecia plicata 3 - 14 7 



Dolerorthis cf. tenuicostata - - 3 - 



Furcitella sp. — — 1 — 



Glyptorthis viriosa — — 2 — 



Kiaeromena sp. 1 — — — 



Leptaena cf. ventricosa - 1 1 1 



Mcewanella sp. - - - 2 



Nicolella actoniae 3 9 6 5 



Onniella ostentata lepida 4 3 9 25 



Orthambonites exopunctata 4 7 12 11 



Palaeoglossa attenuata 1 — — - 



Palaeostrophomena sp. 1 1 1 - 



Petrocrania dubia - - 1 3 



Platystrophia caelata 1222 



Plectorthis whitteryensis - - 7 2 



Rafinesquina sp. — - 1 - 



Reuschella horderleyensis carinata 12 11 6 3 



Salopia sp. — - 2 1 



Skenidioides cf. costatus 1 - 2 1 



Sowerbyella cf. sericea 2 1 1 8 



Triplesia sp. - - - 1 



Whittardia paradoxica 3-82 



association (Williams 1973 : 242), but elements like Bicuspina and Leptaena 

 further suggest that remnants of the Dinorthis association may also be present. 



In conclusion, it is noteworthy that the composition of brachiopod assemblages 

 collected from the Ordovician succession of Shelve appears to be closely connected 

 with the nature of the entombing sediments. In general, two main groups seem to 

 be involved : an inarticulate association connected with the finer clastic sediment 

 and a predominantly articulate one sustained in the coarser, banded, sporadically 

 calcareous siltstones or fine sandstones. Both associations may be traced throughout 

 much of the Ordovician succession with one dominant over the other. Both show 

 profound changes in the composition and relative importance of their constituent 

 taxa and, thereby, greatly reduce the prospects for precise interprovincial correlation. 



IV. SYSTEMATIC METHODS 



The procedure adopted during the systematic study of the Shelve brachiopods was 

 to quantify, wherever possible, any morphological variation displayed by conspecific 

 specimens from any one locality or horizon and evaluate differences detected among 

 congeneric samples by standard statistical tests for significance. This method is 

 similar to that used by the writer during researches on Girvan and Bala faunas 

 (Williams 1962 : 69-79 > I 963 : 333), and requires only a few words of explanation. 



