162 



STRATIGRAPHICAL GEOLOGY 



Echinoderma. Actinocrinus (Glyptocrinus ?) pulclier (fromLlandov.), 

 Periechocrinus moniliformis, Crotalocrinus rugosus, 

 Marsipiocrimis cselatus, Lepadocrinus quadrifas- 

 ciatus. 



Crustacea. Illaenus barriensis, Phacops caudatus (Val. to Lud.), 



P. Downingise, Calymene Bluraenbachii (Bala to 

 Lud.), Encrinurus punctatus, Lichas auglicus (to 

 Lud.). 



Brachiopoda. Atrypa reticularis, Pentamerus galeatus, Strophonella 

 euglypha, Leptfena rhomboidalis (Llau. to Lud.), 

 Orthis rustica, 0. elegantula (Bala to Lud.), Spirifer 

 plicatellus, Retzia? Barrandi, Wilsonia Wilsoni, 

 Camarotcechiaborealis, Cyrtia exporrecta. 



Lamellibranchia. Cardiola interrupta, Grammysia ciugulata. 



Gastropoda. Horiostoraa discors, H. rugosus, Eunema cirrhosis, 



Platyceras (Acroculia) haliotis, Bellerophon dila- 

 tatus. 



Cephalopoda. Orthoceras annulatum, Phragmoceras ventricosuni, 



Gomphoceras pyriforme, Trochoceras asperum, Bar- 

 randeoceras bohemicum. 



Fossils of the Ludlow Series 



Porifera. Ischadites Koanigi, Favospongia Ruthveni. 



Echinoderma. Ichthyocrinus pyrifonnis (from Wenlock), Lap - 

 worthura Miltoni, Palaeaster Ruthveni, Palceocoma 

 Golvini, Palaeodiscus ferox, Echinocystis pomum. 



Crustacea. Homalonotus delphinocephalus (from Wenl. ), H. 



Knighti, Acidaspis coronata, A. Hughesi. 



Arachnida. Pterygotus arcuatus, Eurypterus abbreviatus, Hemi- 



aspis linmloides. 



Brachiopoda. Pentamerus Knighti, Dayia navicula, Camarotoachia 



nucula (from Val. ), Orthis lunata, Chonetes striatella 

 (and var. lata), Orbiculoidea rugata, Lingula cornea, 

 L. Lewisi (from Wenl.). 



Lamellibranchia. Avicula Danbyi (from Val.), Pterinea retroflexa, Car- 

 diola striata, and'C. interrupta (both from Wenl.), 

 Orthonota semisulcata. 



Gastropoda. Cyclonema coralli, Murchisonia coralli, Holopella 



gregaria, Platyschisma hclicites. 



Cephalopoda. Orthoceras bullatum, 0. tenuicinctum, 0. ludense, 



Trochoceras giganteum, Ascoceras Barrandi. 



Pisces. Scaphaspis ludensis, Cephalaspis oruatus, Auchenaspis 



Salteri, Thelodus parvidens. 



C. BRITISH SILURIAN ROCKS 



Range and Relation to Older Rocks. Silurian rocks 

 occupy surface - tracts in the following districts. They form a 

 continuous outcrop of varying width through Wales from Car- 

 marthenshire in the south' to the Denbigh coast 011 the north. 

 They spread westward through Radnorshire and parts of Shropshire, 

 and they reappear from beneath newer rocks as inliers in Stafford- 



