3l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



DESCRIPTION OF PLATE 50 



PAGE 



Lingulella hitka Walcott 312 



Fig. I. (Natural size.) Group of shells flattened on surface of shale. 

 (Locality 6ik.) U. S. National Museum, Catalogue No. 

 60067. 



2. (X 2.) A ventral and a dorsal valve enlarged from fig. i. 



3. (X 2.) A dorsal valve that occurs on fig. i. 



Lingulella chapa Walcott 311 



Fig. 4. (X 3-) A group of shells on surface of shale. (Locality 6ik.) 

 U. S. National Museum, Catalogue No. 60068. 



5. (X 4) A small uncompressed ventral valve. (Locality 6ik.) 



U. S. National Museum, Catalogue No. 60069. 



6. (X 4-) Natural matrix of the interior of a ventral valve. 



(Locality 6ik.) U. S. National Museum, Catalogue No. 

 60070. 



7. (X 4-) A partly exfoliated ventral valve. (Locality 6ik.) 



U. S. National Museum, Catalogue No. 60071. 



8. (X 4-) A small, uncompressed dorsal valve. (Locality 6ik.) 



U. S. National Museum, Catalogue No. 60072. 



9. (X 4) A broader form of the dorsal valve than that repre- 



sented by fig. 8. (Locality 6ik.) LT. S. National Museum, 

 Catalogue No. 60073. 



Mickwitzia muralensis Walcott. (See Plates 51 and 52) 310 



Fig. id. (X 3-) Flattened dorsal valve with excentric apex. (Locality 

 6ik.) U. S. National Museum, Catalogue No. 60093. 

 II. (X 6.) Area about apex and posterior margin enlarged to 

 illustrate surface character. (Locality 6ik.) U. S. Na- 

 tional Museum, Catalogue No. 60094. 

 The specimens represented by figs, i-ii are from locality 6ik. 

 Lower Cambrian : Mahto formation ; dark, hard siliceous shale, 

 northeast base of Mumm Peak above Mural Glacier on the west side 

 of Hitka Pass, 6 miles (9.6 km.) in a direct line north of summit of 

 Robson Peak and northwest of Yellowhead Pass, in western Alberta, 

 Canada. 



