ANNIVERSARY ADDRESS OE THE PRESIDENT. 



75 



South Wales, a great amount of new work has been done by eminent 

 geologists and palaeontologists. Much of the work done by the 

 Survey has had to be readjusted and reconstructed ; the maps then 

 prepared with so much skill by Ramsay, Selwyn, Jukes, Aveline, 

 and others, and which contributed so much to our knowledge, and to 

 the elucidation of the structure of these intricate regions, are now 

 in some areas behind the requirements of the age, through the pro- 

 gress of modern research and nomenclature. The horizons of many 

 of the lowest fossiliferous groups of rocks as now recognized are 

 not expressed or delineated on the Survey maps ; the now well- 

 determined Menevian, Tremadoc, and Arenig rocks of North and 

 South Wales — in other words, all the fossiliferous deposits below 

 the Llandeilo flags, or between that formation and the base of the 

 Tremadoc, are not yet delineated on the maps of the Survey. It 

 may be said by some that the groups of the Harlech, Menevian, and 

 Lingula-flags may be subdivided and placed upon the Survey maps ; 

 but the aspect of these beds and the way they occur in the field will 

 ever prevent this on a 1-inch scale. Transcendentalism in mapping 

 has been, and still is, carried to a greater extent and perfection by 

 the officers of the British Survey than by any other government survey 

 in the world ; and although neither the Tremadoc nor Arenig rocks 

 are recognized on the maps of the Survey, I believe it will be found 

 that these formations have received the fullest recognition and atten- 

 tion in the forthcoming new edition of Prof. Ramsay's ' Geology of 

 North Wales.' 



The Lingula-flags of the Survey and authors generally are equiva- 

 lent to the Middle Cambrian of Sedgwick, and the Upper Cambrian 

 of Lyell and Salter ; the divisions into Lower, Middle, and Upper 

 have long troubled systematists in Britain ; and the extensive 

 and almost hypercritical subdivisions adopted have led to much 

 misunderstanding. The obscurity of these beds in the field, the 

 smallness of the fauna, and the difference in physical condition in 

 areas widely separated often render it a matter of opinion where the 

 lines of demarcation should be drawn, or what should be embraced 

 by the terms Lower, Middle, and Upper Lingula-flags. The so-called 

 Middle group has no value whatever, its fauna consisting of five 

 species only. Three of these are Brachiopoda — Kutorgina cingulata, 

 Lingulella Davisii, and Lingula squamosa. There is one Trilobite 

 {Conocoryphel bucejpJiala, Belt), and also BelleropTion cambrensis, Belt. 

 These last two forms occur in the upper part of the Dolgelly beds 

 of that area, and are said to have been associated with Hymenocaris 

 vermicauda, elsewhere known only in the Lower Lingula-flags. 



We must also remember that the " Lower Lingula-flags " of Sedg- 

 wick are the " Menevian group " of Salter and Hicks, and that the 

 " Ffestiniog group " of Sedgwick constitutes the Middle and Upper 

 Lingula-flags of Salter. Thus the greatest care is required when 

 analyzing or correlating these groups, either through their literature 

 or by research in the field. In the year 1867 the late Mr. Belt* eon- 

 * Geol. Mag. vol. iv. 



