Grabau — Faunas of the Hamilton Group. 295 



Brachiopoda : 



76 Orbiculoidea Lodensis (?). R 



91 Stropheodonta perplana. II 



99 Chonetes scitula. rc 

 100 Chonetes lepida. rc 

 lO-l Strophalosia truncata. R 

 105 Spirifer mucronatus. rc 

 109 S. granulosus, r 

 116 Amboccelia umbonata. r 

 116 (a) A. umbonata var. nana. C 



120 Nucleospira concinna. r 



121 Athyris spiriferoides. R 

 127 Camarotcechia Horsfordi. E 

 129 Camarotcechia Dotis. C 



Anthozoa : 



151 Pleurodictyum stylopora. rc 



152 Streptelasma rectum, r 



Comparing the fauna of this bed with that of the Strophalosia bed, it will 

 be seen that the Hamilton epoch was introduced with a radical change in the 

 fauna, the two beds being as distinct in that respect as possible. The Nautilus 

 bed also differs greatly from all succeeding beds. 



b. The middle Pleurodictyum bed. 



This is the bed in which P stylopora has attained its most abundant and 

 most perfect development. The bed is furthermore characterized by the 

 abundant occurrence of large and robust forms of Spirifer granulosus, many 

 of which are overgrown with bryozoa and corals. 



The fossils of this bed are as follows ; 



Crustacea 



1 Phacops rana. r 



3 Homalonotus Dekayi R 



Cephalopoda : 



Orthoceras sp. r 

 Gasteropoda : 



20 Platyceras Thetis, r 



22 P. symmetricum. R 



