part 4] THE CAMBRIAN HORIZONS OETCOMLET. 325 ' \ 



fa JUL 2 2 1921 *J 



9. The Cambrian Horizons of Cowley (She4j^'©9jBj)| ai^ffiiir^S 

 Brachiopoda, Pteropoda, Gasteropoda, efcT^'By " Etf&AR 

 Sterling Cobbold, F.G.S. (Read April 21st, 1920.) 



[Plates XXI-XXIV.] 



Contents. 



Page 



I. Introduction 325 



II. The Comley Horizons (with Table I) 325. 



III. Classification, Terminology, and References 32& 



IV. Bibliography 326 



V. The Comley Brachiopoda 328 



VI. The Comley Pteropoda, etc 354 



VII. The Comley Gasteropoda 364 



VIII. The Comley Ostracoda 367 



IX. The Faunas of the Comley Horizons (with Table II) and 



their Order of Appearance 368 



X. General Summary 374 



I. Introduction. 



The objects of this paper are to define the horizons of the 

 Cambrian sj^stem at Comley, to describe and illustrate the species 

 of brachiopoda, pteropoda, and gasteropoda, and to discuss 

 the relationships of the faunas -one to the other and to those of 

 other Cambrian areas. 



The majority of the specimens now described were obtained from 

 the excavations carried out between the years 1907 and 1914, on 

 behalf of the Committee for the Excavation of Critical Sections in 

 Palaeozoic Pocks, appointed by the British Association for the 

 Advancement of Science. Some specimens were collected in 1892 

 for H.M. Geological Survey by Mr. J. Phodes, and others have 

 been obtained by mvself or other observers at various dates since 

 1890. 



II. The Comlev Horizons. 



Details of the sections opened by excavation have been given in 

 the reports of the meetings of the British Association held at 

 Dublin in 1908, Winnipeg in 1909, Sheffield in 1910, Portsmouth 

 in 1911, Dundee in 1912, and Manchester in 1915. 



In Table I (facing p. 326) the various horizons from which 

 different assemblages of fossils have been obtained are set out in 

 descending order, with the proposed nomenclature in spaced type, 

 followed by index-letters, thicknesses, general lithological characters, 

 and suggested correlations. The designations used by me in pre- 

 vious communications and in my reports to the British Association 

 are inserted in ordinary type in the first column. Since these 



Q.J.G.S. No. 304. 2 a 



