Correlation of the Silurian of Bohemia. 59 



with J/, priodori, M. vomerinus, Cyrtograptus murchisoni, 

 and Betiolites geinitzianus, the trilobites Arethusina kon- 

 incki Barr., Acidaspis mira Barr., A. prevosti Barr., 

 A. roemeri Barr., and Bronteus planus Corda, which have 

 been many times qnoted as E 2 fossils, although they are 

 confined to E 2 . With them are associated a few brachio- 

 pods, as Leptccna transversalis and Atrypa sappho, which 

 are also met with in E 2 ; and several cephalopods extend- 

 ing into higher zones occur here. 



c. Zone with Monograptus riccartonensis Lapiv. — 

 Chiefly brown or dark fissile calcareous shales with 

 nodules and intercalations of dark compact limestones. 

 Best localities: Lodenice, Vyskocilka, colony "Krejci," 

 Koneprusy. Here have been found: M. riccartonensis 

 Lapw., 12 M. vomerinus Nich., M. dubius Suess var. 

 proceva, M. solitaries n. sp., 71/. validus Per., and M. prio- 

 don Brn. Associated are : Slava bohemica Barr., Apty- 

 chopsis prima Barr., and Arethusina koninchi Barr. 



E^/— Dubius Beds. 



These are characterized by the occurrence of Mono- 

 grapti of the type of M. dubius Suess, and allied forms, 

 such as M. colonics Barr., etc. 13 The shales of these beds 

 very often alternate with seams of calcareous nodules and 

 limestones, in which, besides the rarer graptolites, some- 

 times occur brachiopods, various molluscs, and crinoidal 

 remains. In the northwestern region of Barrande's 

 " Silurian basin" these beds are developed as coral-reef 

 limestones (see section beyond). 



Two zones can be distinguished : 



a. Zone with Monograptus testis Barrande. — Brown 

 or grayish yellow, argillaceous, slightly calcareous shales 

 without concretions or nodules (Barek), or dark shales 

 with concretions and limestone intercalations (Dvorce, 



12 Most of the specimens of this species I formerly considered to belong to 

 M. flemingi Salter and allied forms. The admirable monographs of British 

 graptolites by G. E. Elles and E. M. E. Wood (Mrs. Shakespear) in Paleon- 

 togr. Soc. London 1901-1913 now enable me to undertake a revision of all 

 the British species formerly recorded in my ' ' Etudes, ' ' and to correct some 

 previous determinations. 



13 The original designation, Marr's " colonus zone", I think should be 

 changed to "dubius beds" since M. dubius occurs in the whole of E^, 

 while M. colonus is absent in the lower part. 



