Vol. 56.] FORMATION AND ITS GRAPTOLITE-FAFNA. 419 



known to be of Lower Ludlow age, from beds in Languedoc, 

 the Pyrenees, the Ardennes, and Normandy. Of several of the 

 species he gave descriptions, but no figures. 



In 1895 Lake, 1 in his paper on the 'Denbighshire Series of 

 South Denbighshire,' referred three of his local groups to the period 

 of time intervening between the Wenlock and Aymestry Limestones, 

 and he recognized two distinct graptolitic horizons. His divisions 

 are as follows, in descending order : — 



(3) i Lei?itwardinensis-heds.' > 



(2) Upper gritty beds, unfossiliferous. 



(1) Nantglyn Flags, containing M. Nilssoni and M. colonus. 



(2) Paleeontological. (Graptolites.) 



In 1839 Murchison 2 noted one species of graptolite as being 

 very characteristic of the Upper Silurian strata, and abundant in 

 the Lower Ludlow Beds. This he figured as Graptolithus ludensis, 

 but gave no description of it. 



In 1850 Barrande, in the ' Graptolites de Boheme,' described and 

 figured five new species now known to be confined to beds of 

 Lower Ludlow age, namely Monograptus colonus, M. Bosmeri, 

 M. Nilssoni, M. bohemicus, and M. chimcera. Barrande's memoir 

 gave a great impetus to graptolitic research abroad, and during the 

 next thirty years or so various authorities described and figured 

 graptolites from corresponding beds in Central Europe, as, for 

 example, Suess, 3 Geinitz, 4 Heidenhain, 5 Haupt, 6 Kayser, 7 etc. 



In 1855 M'Coy, in his 'British Palaeozoic Fossils/ pp. 4-5, 

 described what he believed to be Murchison's species ludensis, 

 together with a new form (variety) of this which he named Grapto- 

 lites minor. 



In 1868 Nicholson, in his paper ' On the Graptolites of the 

 Coniston Flags,' 8 recorded three of Barrande's species from the 

 Lake District, namely, M. Nilssoni, M. colonus, and M. bohemicus, 

 and figured and described each of them. He also figured a specimen 

 of M. colonus from the Lower Ludlow Shales of Ludlow. 



In 1873 Mr. Hopkinson, 9 who had collected and studied the grapto- 

 lites from the Lower Ludlow Shales in the typical Ludlow district, 

 recorded several species of Rhabdophora from these beds, but his 

 new species remained undescribed for some years. 



In 1880 Prof. Lapworth 10 described and figured five species of 

 graptolites from the Lower Ludlow Shales of the typical Ludlow 



1 Quart. Journ. Geol. Soc. vol. li, p. 22. 



2 ' Silurian System ' pi. xxvi, fig. 2. 



3 'Ueber Bohmische Graptolithen ' Haidinger's Abhandl. vol. iv (1851) pt. iv, 

 p. 87. 



4 ' Die Graptolithen ... der Grauwackenformation in Sachsen ' 1852. 



5 Zeitsehr. d. Deutsch. Geol. Gesellsch. vol. xxi (1869) p. 143. 



6 ' Die Fauna des Graptolithengesteines ' Neues Lausitz. Mag. vol. liv (1876). 



7 'Die Fauna der altesten Devon-Ablagerungen des Harzes' Abhandl. geol. 

 Specialkarte v. Preussen, vol. ii (1878) pt. iv. 



8 Quart. Journ. Geol. Soc. vol. xxiv, pi. xx, figs. 9-11, 18-19 & 22-24. 



9 Brit. Assoc. Eep. (Bradford) p. 83. 



10 Ann. & Mag. Nat. Hist. ser. 5, vol. v, p. 149. 



