THE UPPER: SILURIAN PERIOD. 127 
Trimerellids ; the old and at the same time modern Zingwle, 
Discine, and Cranieé ; together with many species of Atrypa 
Fig. 68.— Upper Silurian Brachiopods. aa’, Lefptocelia plano-convexa, Clinton 
Group, America; 68’, Rhynchonella neglecta, Clinton Group, America; c, Rhynchonella 
cuneata, Niagara Group, America, and Wenlock Group, Britain; @ a’, Orthis elegan- 
zula, Llandeilo to Ludlow, America and Europe; e e’, Atrypa hemispherica, Clinton 
Group, America, and Llandovery and May Hill Groups, Britain; /_/’, Atvxyfa congesta, 
Clinton Group, America ; ¢ g’, Orthis Davidsoni, Clinton Group, America. (After Hall, 
Billings, and the Author.) 
(fig. 68, e), Leptocelia (fig. 68, a), Rhynchonella (fig. 68, 4, ¢), 
Meristella (fig. 69, a, ¢, f), Athyris, Retzia, Chonetes, &c: 
Niagara Group, America. (After Hall, Billings, and the Author.) 
The higher groups of the A/o/usca are also largely repre- 
sented in the Upper Silurian. Apart from some singular types, 
