I40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



DESCRIPTION OF PLATE 15 



PAGE 



Collenia occidentale (Dawson) in 



Fig. I. (Natural size.) Photograph of a thin-section showing portions 

 of two fragments. U. S. National Museum, Catalogue No. 

 33799. 

 2. (X 8.) Enlargement of the lower, smaller fragment in fig. i. 

 3, 4. (Natural size.) Photographs of two thin-sections occurring 

 in the same stratum of rock as that represented by fig. i. 

 U. S. National Museum, Catalogue No. 33799. 

 5, 6. (Natural size.) Natural sections through two turbinate forms 

 of growth. U. S. National Museum, Catalogue Nos. 60710, 

 60711. 



The specimens represented by figs. 1-6 are from the Algonkian: 

 Chuar terrane; Grand Canyon, Arizona. 



These figures (1-4) were published as figs. 1-4, plate 23, Bull. Geol. 

 Soc. America, Vol. 10, 1898, Walcott : Pre-Cambrian fossiliferous 

 formations. 



Collenia compacta Walcott 112 



Fig. 7. (Natural size.) Natural weathered vertical section showing 

 the club-shaped growth on the left with the irregular 

 lamellse about it on the right. U. S. National Museum, 

 Catalogue No. 60712. 



From locality 400a: Algonkian: Siyeh limestone; Continental 

 Divide at head of Kipps Creek, Glacial National Park, Montana. 



