Fig. 52 

 Ordovician Brachiopods : 1, Lingula rectilateralis; 2, Orbiculoidea tenuistriata; 

 3, 4, 5, 6, Plectambonites sericeus; 7, Plectambonites centricarinatus; 8, 

 Plectorthis whitfieldi; 9, 10, 11, Ploesiomys retrorsa; 18, Ploesiomys por- 

 cata; 14, 15, Clitambonites americanus. (From Ruedemann, N. Y. State 

 Mus. Bui 162.) 



