ANNIVERSARY ADDRESS OF THE PRESIDENT. 



165 



find a large proportion absolutely restricted to that horizon. Of 

 such restricted species in the true Wenlock rocks (limestones and 

 shales) we have 24 or 25 per cent. None of the following species 

 occurs in any other horizon ; and they may therefore be accepted as 

 definitely typical Wenlock species — Atrypa Barrandii, Dav., Cra- 

 nia Grayii, Dav., C. Sedgwichii, Lewis, C. siluriense, Dav., Cyrtia 

 nasuta, Lewis, Leptama segmentum, Aug., Meristella nitida, Hall, 

 Nueleospira pisum, Sow., Obolus Davidsoni, Salt., rbiculoidea 

 Becketiana, Dav., Orthis cequivalvis, Dav., 0. bascdis, Dalm., 0. 

 Lewisii, Dav., 0. Hughesii, Dav., Metzia Salteri, Dav., Siphonotreta 

 anglica, Mor., Spirifera sulcata, His., Strophomena Dayi, Dav., S. 

 Fletcheri, Dav., S. Hendersoni, Dav., S. Orbignyi, Dav., S. Walm- 

 stedti, Linds., S. IValtoni, Dav., and Triplegia MacCoyana, Dav. 



The Wenlock Brachiopoda of Scotland number 11 genera and 20 

 species, most of them belonging to the long-range species, the more 

 restricted being Meristella Maclareni, Hasw., Nueleospira pisum, 

 Sow., Orthis Leiuisii, Dav., 0. ivenlocJcensis, Dav., 0. poly gramma, 

 Sow., and Strophomena Hendersoni, Dav. 



The Irish Wenlocks contain 11 genera and 31 species ; the most 

 important are Obolus Davidsoni, Salt., Pentamerus undatus, Sow., 

 lihynchonella Beltiana, Dav., H. chjlexa, Sow., Orthis rustica, Sow., 

 Spirifera bijugosa, M'Coy, and Strophomena Dayi, Dav. The genera 

 numerically rich in species are Orthis (16 species), Rhynchondla 

 (10), Spirifera (8), Strophomena (16), Pentamerus (6), Meristella 

 (5), and Atrypa (5). The rarer genera are but feebly represented. 

 12 genera and 32 species pass to the Lower Ludlow, 10 genera and 

 26 species appear in the Aymestry, and 11 genera and 17 species in 

 the Upper Ludlow. Again, the "Wenlock is allied to the Caradoc 

 and Llandovery groups through 11 genera and 41 species, 39 being 

 Upper Llandovery, 22 Lower Llandovery, and 14 Caradoc species ; 

 5 Llandeilo species lived on through all five periods, viz. Leptcena 

 sericea, Orthis biforata, 0. calligramma. 0. elegantula, and Stropho- 

 mena rhomboidalis. 



Lamellibranchiata. — Out of the 16 genera and 44 species of 

 bivalve shells ranging through the Wenlock rocks, the upper divi- 

 sion or Wenlock Limestone yields 43 species, the one absent or 

 uncertain form beiDg doubtfully Lunulacardium aliforme, Sby. 



The Tarannon Shale contains, so far as we kuow, only 2 species, 

 and both are Upper Llandovery shells, Pterincea pla.mdata, Conrad, 

 and P. retrofiexa, Wahl. ; both pass to the Ludlow beds. The Den- 

 bighshire Grits from all available sources yield 7 genera and 10 

 species. The Woolhope only 3 genera and 5 species : these, with 

 the Denbighshire-grit species, are all Upper Wenlock also. The 

 local stratigraphical position of the "Woolhope or Barr" Limestone 

 carries with it occasionally a peculiar fauna, and, although strictly 

 of Wenlock age, there is always uncertainty as to the occurrence of 

 few or many species, but it is next in numerical value to the Upper 

 Wenlock. The Wenlock rocks of North Wales furnish 8 genera 

 and 14 species, Pterincea, Cardiola, and Cucullella being the chief 

 genera. Pterincea has yielded 6 species, Cardiola 3, and Cucullella 

 vol. xxwii. n 



