ANNIVERSARY ADDRESS OF THE PRESIDENT. 





1 out of 10 



Hydrozoa 



1 





36 



Coelenterata 



20 



>•> 



40 



Annelida 



2 



99 



15 



Echinodermata . . . 



. 2 



55 



32 





16 



35 



146 



Bryozoa 



4 



99 



21 



Brachiopoda 



33 



53 





m PllilrraTinma \c\ 



J^CLi-U.Ci_Ll Ul clllL/ULl CI LcX . 



. 3 



33 



76 





10 



99 



53 



Pteropoda 



1 



59 



12 



Heteropoda 



1 



33 



15 





. 7 



93 



47 





101 



95 



612 



Pass to Lower 

 Llandovery. 



The important zoological groups in the Caradoc are therefore the 

 Hydrozoa, Coelenterata, and Echinodermata — the latter especially 

 through the Cystideans, no less than 8 genera and 23 species illus- 

 trating this rare group. The Crustacea number 146 species, of which 

 106 are peculiar; 20 species are from the Llandeilo and 16 pass 

 upwards to the Lower Llandovery, leaving thus for the Caradoc 

 and Bala beds the largest Crustacean fauna known in the Lower 

 Palaeozoic rocks. Only 4 species of Bryozoa out of the 21 appear to 

 pass to the Lower Llandovery ; and they all commence in the 

 Caradoc : they are Fenestella subantiqua, d'Orb., Ptilodictya dicho- 

 toma, Portl., P. coslellata, M'Coy, and P. lanceolata, Goldf. We 

 should expect more species in common in this group, from the fact 

 of their being usually a moderately deep-sea family, and less subject 

 to vicissitude or change than littoral or sublittoral species. The 

 Brachiopoda of the Caradoc and Bala group number 109 species, 

 representing 16 genera ; they are more numerous than in other of 

 the Palaeozoic rocks. 33 of the 109 pass to the Lower Llandovery ; 

 and we have seen that the connexion with the Llandeilo below is 

 through 26 species, leaving, therefore, 50 as Caradoc proper. As 

 regards geographical distribution, N"orth-"Welsh forms greatly pre- 

 dominate, owing probably to the larger amount of research to which 

 the rocks of the four counties of Caernarvon, Denbighshire, Mont- 

 gomeryshire, and Merioneth have been subjected. Ireland also has 

 yielded 60 species, and Scotland 40. Their more complete* distribu- 

 tion will be further discussed under that head. 



The littoral or shallow-sea condition of the Caradoc is further 

 illustrated by the occurrence of a large number of bivalve Mollusca. 

 No less than 76 species are known ; and of these only 3 species pass 

 to the Lower Llandovery, viz. Pterincea retrqflecca, Wahl., Orthonota 

 sulcata, His., and Mytilus mytilimeris, Conr. ; and 2 of these 3 forms 

 pass to the Ludlow and the "Upper Llandovery, viz. Pterincea retroflexa 

 and Mytilus mytilimeris ; so that 66 species of Lamellibranchata be- 

 long to the Caradoc exclusively ; and, strange as it may appear, these 

 3 are the only species known in the whole of the Lower Llandovery. 



