ANNIVERSARY ADDRESS OF THE PRESIDENT. 



fined to the Lower Devonian. The Middle Devonian is represented 

 by 13 genera exhibiting 23 species — Aviculopecten 2 species, Pteri- 

 ncea 6, Anodonta JuJcesii, Cleidophorus ovatus, Corbula Hennahi* 

 Cucuttcea Hardingii, G. trapezium, Ctenodonta lineata, Leptodomus 

 constr ictus, Megalodon 3, Modiola scalaris, Pleurorhyncbus 2, Pul- 

 lastra antiqua, and Sanguinolaria elliptica. Megalodon, Pleurorhyn- 

 chus, Corbula, and Cleidophorus are generically and specifically essen- 

 tially Middle Devonian. Cucullaxi 6 species, Curtonotus 6, Cteno- 

 donta 4, are the larger genera of the Upper Devonian beds of North 

 Devon, south of the latitude of Baggy Point ; but we have seen how 

 few pass to the Carboniferous south of Barnstaple and Pilton, or along 

 the strike of the two formations from Barnstaple to Braunton. The 

 South-Petherwin and Land-lake beds in North Cornwall are Upper 

 Devonian, and have jdelded 65 species ; they cannot be affiliated with 

 the Carboniferous, the Clymenice and species of Orthoceratida? for- 

 bidding it. 



Any comparison of the insignificant British fauna with the splendid 

 series of Devonian species in Europe and America is useless : no fewer 

 than 90 genera and 900 species of Lamellibranchiata have been de- 

 scribed ; 260 are Monomyarian and 640 are Dimyarian species. 



Gasteropoda. — 13 British genera and 45 species constitute the 

 entire list of the Odontophora. No species occurs in the Lower Devo- 

 nian. The Middle, as in the case of all the other classes, contains the 

 largest number of species (36) and 12 of the 13 genera — Acrocidia 

 3 species, Euomphalus 5, Loxonema 5, Macrocheilus 6, Murchisonia 4, 

 Nerita 1, Pleurotomaria 6, Scoliostoma 1, Trochus 1, Turbo 2, and 

 Vermetus 2 species. The Upper Devonian species are 14, and occur 

 mostly in the Pilton, Brushford, and Petherwin areas ; they represent 

 7 genera — Acrocidia 1, Euomphalus 1, Loxonema 4, Macrocheilus 1, 

 Murchisonia 1, Natica 2, and Pleurotomaria 4. 5 species pass to the 

 Carboniferous — Acrocidia vetusta, Loxonema rugiferum, L. tumidum, 

 Murchisonia angulata, and M. spinosa. 



The South-Devon area has yielded 37 of the 45 Middle Devonian 

 species, North Devon only 5, viz. Euomphalus serpens, E. radiatus, 

 Acrocidia vetusta, Macrocheilus brevis, and Natica meridionalis, 

 and 11 Upper Devonian ; the Petherwin beds in North Cornwall 

 contain 7 Gasteropods, all Upper Devonian. Complete comparison 

 of the two areas will be made at the end of the Devonian fauna. 



Pteropoda. — No Conularia or Theca has appeared in the Devonian 

 rocks of either South or North Devon. 30 species are known in 

 the Devonian rocks of Germany and America. 



Heteropoda. — The order Nucleobranchiata through the AtlantidaB 

 is represented in all three divisions of the Devonian rocks by Belle- 

 rophon (5 species) and Porcellia (3). Bellerophon bisulcatus occurs in 

 the Lower and Upper divisions; B. striatus, Lower and Middle; 

 B. hiulcus, B. subglobatus, and B. JJrii in the Upper ; B. hiulcus and 

 B. JJrii appear also in the Carboniferous rocks. B. subglobatus is also a 

 Coomhola species (Irish). Porcellia Woodwardi, Sow., and P. striata, 

 Phill., occur in the Middle Devonian of South Devon ; but P. Symondsii 

 has hitherto only been found in the Upper division, or Pilton and Barn- 



