C2 CARBONIFEROUS TRILOBITES 



reason to include with them representatives of at least a portion of the true Coal- 

 Measures, and possibly also of the Carboniferous Limestone." 



(1) The North Devon series of Carboniferous deposits about Barnstaple and 

 Bamptori is thus given by Prof. Phillips (p. 189) •} 



(a) " Upper part anthracitiferous, and containing ironstone, and by these 

 characters agreeing with the Coal-deposits of Pembrokeshire. This is in general 

 a Gritstone series, with plants of the Coal-formation." 



(b) " Coddon Hill cherts, black-grits, jasper-rock, lydian-stones and shales of 

 considerable, but variable, thickness ; 1500 to 2000 feet (according to the Rev. 

 D. Williams)." 



(c) " Limestone and black shale with Posidonomya, Goniatites, &c. = Posido- 

 nomya (Posidonia) limestone of Swimbridge and Venn." 



(d) " Black shale group." 



(2) The South Devon strata about Trescott and Lew Trenchard have been 

 thus divided (op. cit., p. 194) : 



(a) " Gritstone group of Central Devon." 



(b) " Upper shale group — dark shales, carbonaceous grits and shales (equal to 

 the Coddon Hill series." 



(c) " Calcareous group — limestone of dark colour, and irregular bedding, with 

 shales (Posidonomya)." 



(d) "Lower shale group, with few fossils (no slaty cleavage)." 



1832. — Dr. A. Geikie, F.R.S. (the present Director- General of the Geological 

 Survey of Great Britain), writes in his ' Text-Book of Geology' (p. 748) as follows : 



" In Moravia, Silesia, Poland, and Russia, the Carboniferous Limestone 

 reappears as the base of the Carboniferous system, but not in the massive calcareous 

 development which it presents in Belgium and England. One of its most charac- 

 teristic phases is that to which the name ' Culm ' (applied originally to the 

 inferior slaty coal of Devonshire) has been given, when it becomes a series of 

 shales, sandstones, greywackes, and conglomerates in which the abundant fauna of 

 the limestone is reduced to a few molluscs {Productus antiquus, P. latissimus, P. 

 semi-reticulatus, Posidonomya Becheri, Goniatites sphcericus, Orthoceras striatulum,* 

 &c). The Posidonomya particularly characterises certain dark shales known as 

 ' Posidonomya schists.' About fifty species of plants have been obtained from 

 the Culm, typical species being Catamites transitionis, Lepidodendronveltheimianwm, 



1 ' Figures and Descriptions of the Palaeozoic Fossils of Cornwall, Devon, and West Somerset,' 

 by Prof. John Phillips, F.E.S., 1841. 8vo. 



2 = O. striolatum, Sandb. The above-mentioned shells, which are all marine, occur in the Calci- 

 ferous Sandstone around Edinburgh and in Fifeshire (see paper by Mr. E. Etheridge, junr., " On the 

 Invertebrate Fauna of the Lower Carboniferous or Calciferous Sandstone of Edinburgh, &c," Quart. 

 Journ. Geol. Soc, 1878, vol. xxxiv, pp. 1 — 26, plates i and ii). 



