ANNIVERSARY ADDRESS OF THE PRESIDENT. 1 35 



species each, occur in any one locality, as in Shropshire, Scot- 

 land, and Ireland. North and South Wales have yielded only 2 

 genera, each with 2 species, in any of the six counties. The 

 Actinozoa even afford us stronger evidence still of the importance 

 of specific evidence. In this class we know through the fullest 

 research that 20 genera and 40 species occur, thus averaging only 

 2 species for each genus. Many genera (13) have as yet yielded 

 only 1 species ; they are Plasmopora, Syringophyllum, Holy sites, 

 Stylarcea, Omphyma, TJiecostegites, Alveolites, Aulacopliyllum, Calo- 

 stylis, Oyathophyllum, Fistulipora, Tredadium, and Prosopora. We 

 cannot suppose for one moment that these genera are not repre- 

 sented by more species ; it is a matter of research only. The 

 genus Favosites has 8 species, Heliolites 6, Petraia 6, and Monti- 

 culipora 4. The 20 genera make 90 appearances through the 

 10 areas, and the species 188 ; 32 of the generic and 68 of the 

 specific appearances occur in the formations above the Caradoc, 

 and show the relation of one group of strata to another, as deter- 

 mined through palaeontological research. The Lower Llandovery, 

 which succeeds or is the natural termination of the Caradoc, con- 

 tains 9 genera and 20 species of the whole fauna (f§); and the 

 Upper Llandovery 6 genera and 17 species of the whole. The 

 coral fauna of the Caradoc at once makes its appearance underived, 

 the older Llandeilo possessing only 3 species of Actinozoa, Halysites 

 catenularius, Favosites Jibrosus, and Monticuliporafrondosa; whereas, 

 next to the Wenlock, the Caradoc possesses the largest Ccelenterate 

 fauna of the Lower Palaeozoic rocks. Nowhere, either in Europe 

 or America, does this class appear with so large a generic grouping. 

 20 of the 40 species pass to the Lower Llandovery ; most of the 

 same appear in the overlying and unconformable Upper Llandovery. 



The Crustacea pre-eminently characterize the Caradoc and Bala 

 rocks, and constitute the largest group in the whole of the Palaeo- 

 zoic series ; 37 genera and 146 species have been collected, de- 

 scribed, and registered through the labours of the Geological Survey 

 of the three countries, England, Ireland, and Scotland, as well as 

 by the researches of Sedgwick, Salter, M'Coy, Baily, Sharpe, Prof. 

 Hughes, &c. No zoological group is better understood, none more 

 important to the student of stratigraphical geology. The Lower, 

 Middle, and Upper Bala beds could with difficulty be read or under- 

 stood without a minute acquaintance with the Trilobita of this vast 

 middle series of Lower Palaeozoic deposits. They are to this group 

 of rocks what the Ammonitidae and Echinidae are to the Mesozoic 

 series. The order Trilobita is illustrated by 27 genera, the re- 

 maining 10 are mostly Ostracoda ; among them is Turrilepas. 





'Caernarvonshire has 



yielded 



11 genera and 17 species 



North 



Denbighshire 



?? 



17 „ 



33 „ 



Wales. 



Montgomeryshire 





13 „ 



29 „ 





Merionethshire 





16 „ 



36 „ 



South 1 



' Pembrokeshire 



JJ 



16 „ 



24 „ 



Wales. ; 



Caermarthenshire 



55 



13 „ 



20 „ 



12 



