226 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



DESCRIPTION OF PLATE 33 



PAGE 



Carnarvonia venosa Walcott 189 



Fig. I. (Natural size.) Dorsal view of the two valves of the carapace 

 flattened on the surface of the shale. The adductor muscle 

 scar (adm) shows through the test, and the fine venation 

 extending from the head portion backward is beautifully 

 shown. U. S. National Museum, Catalogue No. 57719. 



The specimen illustrated by fig. i is from locality (^^^ ] Middle Cam- 

 brian : Burgess shale member of the Stephen formation (about 75 feet 

 above the phyllopod bed near the base of the shale), on the west slope 

 of the ridge between Mount Field and Wapta Peak, one mile (1.6 km.) 

 northeast of Burgess Pass, above Field, British Columbia. 



Tusoia retifera Walcott 187 



Fig. 2. (Natural size.) View of flattened right valve showing reticu- 

 late surface markings. U. S. National iMuseum, Catalogue 

 No. 57720. 



The specimen illustrated by fig. 2 is from locality (35k) Middle 

 Cambrian : Burgess shale member of the Stephen formation, on the west slope 

 of the ridge between Mount Field and Wapta Peak, one mile (1.6 km.) 

 northeast of Burgess Pass, above Field, British Columbia. 



