i58 



PEOCEEDINGS O? THE GEOLOGICAL SOCIETY. 



Llandovery series. 4 genera and 9 species pass to the Wenlock. 

 Ireland has only 2, Orthoceras coralUforme, M'Coy, and 0. subgre- 

 garium, M'Coy. Badnorshire has 1 species, Lituites cornu-arietis. 

 Sow. Taking South Wales generally, only 6 species are known 

 there, and these represent 4 genera — Actinoceras 1 species, Lituites 

 1 species, Orthoceras 3 species, and Tretoceras 1 species. 



The Upper Llandovery rocks of Scotland give us 4 species, 

 3 Orthocerata and 1 Pliragmoceras (P. corner essum). 



We therefore find that, out of the whole fauna of the Upper 

 Llandovery rocks, numbering 240 species, only 91 are confined to 

 them and do not pass up. The following list shows the special 

 Upper Llandovery fauna : — ■ 



Protozoa 



Actinozoa 10 



Echinodermata 3 



Crustacea 8 



Bryozoa 3 



Brachiopoda 22 



Lamellibranchiata 11 



Gasteropoda 17 



Pteropoda 1 



Heteropoda 5 



Cephalopoda 9 



2 species. 



91 



Wenlocb:. 



I have stated that 58 genera aud 125 species are common to the 

 "Wenlock rocks and the Upper Llandovery ; in other words, these 

 125 species pass up from the Llandovery to the Wenlock formation. 

 Next to the Caradoc and Bala, the Wenlock group, embracing the 

 Tarannon Shales, Denbighshire Grits, and Woolhope beds, possesses 

 the largest Silurian fauna known ; it numbers 168 genera and 530 

 species. Eight chief groups or classes out of the fourteen furnish the 

 majority of the species, in each case attaining their maximum in the 

 Wenlock Limestone. They are the following : — 



1. Hydrozoa 6 genera and 30 species. 



2. Actinozoa 25 „ 76 „ 



3. Echinodermata 28 genera and 68 species. 



4. Crustacea 27 „ 78 „ 



5. Brachiopoda 21 



6. Lamellibranchiata .... 16 



7. Gasteropoda 9 



8. Cephalopoda 5 



101 

 45 

 27 



30 



I may add the Bryozoa, for at no period in the history of the 



