164 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Atrypa reticulata. 

 Chouetes striatellus. 

 Crania hnplicata. 

 Leptasna transversalis. 

 Meristella tumida. 

 Or this elegantula. 



E-hynchonella nucula. 

 Spirifera elevata. 



exporrecta. 



Strophoinena pecten. 

 rhomboidalis. 



All those named have appeared in the Llandovery or Caradoc 

 before, and all pass to the Ludlow ; but their universality through 

 the Wenlock renders them conspicuous or long-lived, though not 

 perhaps the best witnesses in determining the age of any particular 

 horizon through the Wenlock deposits ; those species which are 

 short-ranged, or essentially typical or confined to particular beds, 

 should be named, as contradistinguished from those given above. 

 No species is peculiar to the Tarannon Shale, although 10 genera 

 and 15 species range through this series of beds. No species essen- 

 tially marks, distinguishes, or is confined to the Denbighshire Grits ; 

 yet 14 genera and 19 species also occur in this horizon. 



Although 17 genera and 56 species are known in the Woolhope 

 beds, yet only 2 species are restricted to them ; these are Orthis 

 mullochensis, Dav., and Pentamerus undatus, Sby. This last species 

 occurs in the "Woolhope (?) of Ireland. 



Every Tarannon species except Lingida Symondsii had previously 

 occurred, or apx>eared in one or other of the two Llandovery horizons 

 or in the Caradoc. All the species in the Denbighshire Grits except 

 three, Discina 2forrisii, Meristella tumida, and HJiynchonella navicida, 

 also have appeared in and passed up from the same deposits. Thus 

 we find that the restricted Brachiopodal fauna (so far as we at pre- 

 sent know) in these beds at the base of the Wenlock is extremely 

 scanty. 



Out of the 101 known Wenlock species, 56 had not occurred in 

 any earlier formation, but first appeared in the Woolhope and 

 Wenlock Limestone ; these newly introduced Wenlock forms repre- 

 sent 20 genera. I deem it important to name them and give the 

 numbers of the species in each genus ; they are : — 



Athyris 3 species. 



Atrypa 2 „ 



Crania 3 ., 



Cyrtia 1 



Discina 4 „ 



Eickwaldia 1 ,, 



Leptasna 2 



Lingula 2 



Meristella 4 „ 



Nucleospira *. 1 „ 



Obolus 3 species. 



Orbiculoidea 2 



Orthis 6 



Pentamerus 3 



Eetzia 2 



Ehynchonella 4 



Siphonotreta „ 1 



Spirifera 3 



Strophomena 8 



Triplesia 1 



Out of so large a fauna as 101 species, 96 of which occur in one 

 division (the Wenlock Limestone and Shale), we should expect to 



