Figure 27 Lower and Middle Cambrian fossils. G, Middle 

 Cambrian. (Brachiopods, A, B ; pelecypod, C; gastropod, D, E; 

 conularids, F, G; trilobites, H-K). A Obohlla gemma, x6. B 

 0. crassa, x3. C Fordilla (Aristozoe ?) troyensis, x2. D, E 

 Stenothe^ca rugosa, x2. F HyolitJies communis, x2. G H. ameri- 

 camis, x2. H Microdiscus speciosus, x2. / Atops trilineata, x^. 

 J Olenoides fordi, x2. K Olenelhts thompsoni, x^4. 



