THE UPPER SILURIAN PERIOD. 



127 



Trimerellids ; the old and at the same time modern Lingulce, 

 Discince, and Crania ; together with many species of Atrypa 



fig. 68. Upper Silurian Brachiopods. a a', Leptoccelia plano-convexa, Clinton 

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

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

 tuta, Llandeilo to Ludlow, America and Europe; e e , A try fa. hemispherica, Clinton 

 Group, America, and IJandovery and May Hill Groups, Britain ;//', Atrypa congesta, 

 Clinton Group, America ; g g 1 , Orthis Davidsoni, Clinton Group, America. (After Hall, 

 Billings, and the Author.) 



(fig. 68, e), Leptocalia (fig. 68, a), Rhynchoiiella (fig. 68, /;, c) t 

 Meristella (fig. 69, a, ,f], Athyris^ Reizia, Cuonetes, &c. 



Fig. 69. a, n! Meristella intermedia, Niagara Group, America; b, Spirifera Niagar- 

 ensis, Niagara Group, America; c c , Spirijcra crispn, May Hill to Ludlow, Britain, and 

 Niagara Group, America ; d, Stroflwtnena (Streptorhynchris) subplana, Niagara Group, 



/, Meristella cylindrica. 



America ; e, Meristella namfortni*. N 

 Niagara Group, America. (After Hall 



Group, Amer 

 illings, and the At 



The higher groups of the Mollusca are also largely repre- 

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



