Correlation of the Silurian of Bohemia. 67 



mal" E 2 fauna ; a considerable part is, however, common 

 to E 2 and F x . It is characterized by numerous species of 

 Hercynella, which are regarded by some paleontologists 

 as pelagic Pulmonata. 20 Moreover, cephalopods (40 

 species, badly preserved, enumerated by Barrande and 

 Novak), large lamellibranchs (Panenka, Prcducina, Modi- 

 olopsis, Dalila, Cypricardinia, Hemicardium, Avicula), 

 gastropods (St ropho stylus, Potellomphalus, Stylonema), 

 Conularia, and Tentacidites, are other prominent groups ; 

 a noteworthy feature is the thin shell of the molluscs men- 

 tioned. Graptolites are represented by two last species, 

 Monograptus hercynicus and M. kayseri Per. 



Concerning the more detailed division of these F 1 beds, 

 I must content myself with giving a brief recapitulation 

 of results published elsewhere, 21 and adding some further 

 remarks. In the " normal " F x can be distinguished three 

 horizons, which are not sharply delimited, as follows : 



1. The lowest consists of dark or black thick lime- 

 stones, alternating with thick beds of shales ; it contains 

 rare fish remains (M achcer acanthus , and some new genera 

 resembling Ateleaspis, Aspidichthys, Cyathaspis, Dinich- 

 thys, Macro pet alichthys, and Mylostoma). Other fossils 

 are also rare. 



2. Fine-grained limestones, thinly bedded, alternating 

 with shales. The greater part of the F x fossils occur 

 here. Characteristic ones are: Hercynella nobilis, PL. 

 radians, H. bohemica, H. paraturgescens, Rotellomphalus 

 tardus, Strophostylus gregarius var. proeva, Stylonema 

 solvens, Dalila obtusa, D. reseda, Lunulicardium analo- 

 gum,L. evolvens, Panenka amcena, P. grata, Ceratiocaris, 

 Aristozoe, Pygocaris, and Gigantostraca. 



3. Shaly limestones and shales (black, brown or gray) , 

 with Monograptus hercynicus and M. kayseri. Spirifer 

 inchoans is very abundant, and the following species are 

 common: S. nerei, Atrypa canalicidata, Pentamerus 

 janus, P. linguifer, Cyrtia trapezoidalis, Avicula migrans, 

 A. pusilla, and Conocardium aptychoides. In the upper 

 part of this horizon also appear trilobites. Common 

 among them and very characteristic (confined to FJ is 



20 These are wanting in the reef limestone of F 2 (Koneprusy) and reappear 

 in the shaly limestones of G^ 



21 Centralblatt f. Min. u. Geol., 19-20, 318-322, 1918. 



