ANNIVERSARY ADDRESS OP THE PRESIDENT. 



IOI 



distinctness of the Arenig from the succeeding Llandeilo is clear, 

 both physically and paheontologically. The following table exhibits 

 most of the type forms occurring in the Arenig and the Llandeilo : — 



Ogygia peltata 



Selwynii 



Calyinene parvifrons . 



iEglina binodosa 



grand is 



caliginosa 



Trinucleus Murcbisoni 



G-ibbsii 



Orthoceras Avelinii 

 Obolella plurnbea . . . 

 Cucullella anglica 

 Encrinites, ? sp. ... 



Asapbus tyrannus 



peltastes 



Ogygia Bucbii, Tar. convexa 



Calymene cambrensis 



Trinucleus favus 



Licbas patriarcbus , 



Belleropbon bilobatus 



Helicotoma 



Lingula granulata 



attenuata 



Ortbis striatula 



calligrauima , 



Ctenodonta, ? sp , 



Ogygia (Asapbus) corndensis 



Bucbii 



Barrandia (Ogygia) radians 



Oordai , 



Calymene duplicata 



Trinucleus fimbriatus 



Cbeirurus Sedgwickii 



Ampyx nudus 



Agnostus Maccoyi 



Lingula Bamsayi 



Belleropbon perturbatus 



Murcbisonia simplex 



Modiolopsis inflata 



Didymograptus Murcbisoni 

 Ortbis calligrauima 



12 



© 5 

 o s 



*? 



14? 



la a 



16 



St. David's, Whitesand Bay, 

 Stipersfcones and N. Wales. 



f Tai-birion,near Arenig-fawr. 



\ Shropshire. 



Cefn-y-Grwynlle (Stiper- 



stones). 

 Wbitesand Bay. 

 Stiperstones. 



I Every w 



Everywhere in L. Llandeilo. 



Fairfacb, near Llandeilo. 



Gilwern, near Builtb. 

 Abereiddy Bay. 



)■ Builth and Abereiddy Bay. 



Abereiddy. 

 Builth. 



" The great break in organic life between the Tremadoc slates 

 and the Arenig or Skiddaw group determined Salter, after working 

 vol. xxxvn. i 



