796 DR F. R. C. REED ON THE 



As in the case of all the groups of invertebrates found in the Ordovician and 

 Silurian beds of the Girvan area, most of the advance now made in our knowledge 

 of the brachiopod fauna is due to the indefatigable and long-continued labours of 

 Mrs Robert Gray, who has amassed an immense and unique collection of specimens 

 which have been freely placed at my service. 



It is therefore principally upon fossils in her possession that the following work 

 is based. But all the available -material in the museums in London, Edinburgh, 

 Cambridge and elsewhere has been utilised in the preparation of this memoir, and 

 my thanks are due to the various authorities who have afforded me the requisite 

 facilities for my work. 



The references to the synonymy of the species have been restricted to the type 

 descriptions, the British examples, and Davidson's Monograph, except in a few cases 

 where additional references appeared necessary. 



As far as possible unverified synonyms have been omitted, and foreign records 

 of the occurrence of British species abroad have not been quoted, though a different 

 practice is not unusual in geological literature. 



The collections of Girvan brachiopods which have been examined in connection 

 with this memoir are indicated by numbers in their order of importance as follows : — 



(1) Mrs Gray's collection. 



(2) Museum of Practical Geology, Jermyn Street. 



(3) Sedgwick Museum, Cambridge. 



(4) Hunterian Museum, University of Glasgow. 



(5) Geological Survey Museum, Edinburgh. 



(6) Royal Scottish Museum, Edinburgh. 



(7) British Museum (Nat. Hist.), South Kensington. 



The classification and order of treatment of the genera is that employed by 

 Schuchert in the second edition of the translation of Zittel's Text-book of 

 Paleontology, vol. i, 1913. 



Stratigraphical Classification. 



The horizons from which the species here described have been obtained are 



shown in the following table : — 



' Penkill Group. 



_,.. . Camregan Group. 



Silurian 4 ° n 



Saugh Hill Group. 



. Mulloch Hill Group. 



Drummuck Group. 

 Whitehouse Group. 

 Ordovician^ Balclatchie Group. 



Stinchar Limestone Group. 

 Ballantrae Group. 



