THE UPPER SILURIAN PERIOD. 



127 



Trimerellids ; the old and at the same time modern Li?igtdcBj 

 Discmce^ and Cranice ; together with many species oi Atrypa 



Fig. 68. — Upper Silurian Brachiopods. aa, Leptocoelia plano-convexa, Clinton 

 Group, America ; b b', Rkynchonella neglecta, Clinton Group, America ; c, Rhynchonella 

 cuneata, Niagara Group, America, and Wenlock Group, Britain ; d d' , Orthis elegan- 

 tula, Llandeilo to Ludlow, America and Europe; e e' , Atrypa hemispherica, Clinton 

 Group, America, and Llandovery and May Hill Groups, Britain ;//', Atrypa co7igesta, 

 Clinton Group, America ; g g' , Orthis Davidsoni, Clinton Group, America. (After Hall^ 

 Billings, and the Author.) 



(fig. 68, <?), Leptoccelia (fig. 68, a), Rhyncho7iella (fig. 68, b^ c), 

 Meristella (fig. 69, a, e,f), Athy7-is, Hetzia, Chonetes, &c. 



Fig. 69. — a, a' Meristella intermedia, Niagara Group, America ; b, Spirifera Niagar- 

 ensis, Niagara Group, America ; c, c , Spirifera crispa, May Hill to Ludlow, Britain, and 

 Niagara Group, America ; d, Stropho7nena {Streptorkynchus) stibplana, Niagara Group, 

 America ; e, Meristella naviformis, Niagara Group, America ;/, Meristella cylindrica, 

 Niagara Group, America. (After Hall, Billings, and the Author.) 



The higher groups of the Mollusca are also largely repre- 

 sented in the Upper Silurian. Apart from some singular types, 



