64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



REFERENCES 



Deiss, Charles. 



1938. Cambrian formations and sections in part of Cordilleran Trough. 



Bull. Geol. Soc. Amer., vol. 49, pp. 1067-1168. 



Mansfield, G. R. 



1929. Geography, geology and mineral resources of the Portneuf quad- 

 rangle, Idaho. U. S. Geol. Surv. Bull. 803. 



Resser, C. E. 



1939. The Spence shale and its fauna. Smithsonian Misc. Coll., vol. 97, 



No. 12. 

 Richardson, G. B. 



1 91 3. The Paleozoic section in northern Utah. Amer. Journ. Sci., vol. 36, 

 pp. 406-416. 

 Walcott, C. D. 



1908. Nomenclature of some Cambrian Cordilleran formations. Smith- 

 sonian Misc. Coll., vol. 53, No. 1. 

 1908. Cambrian sections of the Cordilleran area. Smithsonian Misc. Coll., 

 vol. 53, No. 5. 



EXPLANATION OF PLATES 



All figures are natural size unless otherwise marked. Localities are given 

 only when other than 54s. 



Plate i 



page 

 Micromitra haydeni Walcott 20 



1. Ventral valve (Walcott fig. B) (X4)- 



2. Dorsal valve (Walcott fig. C) (X4)- 



3. Holotype dorsal valve (Walcott fig. A) (X 5)- 



Paterina hirta, new species 20 



4. Dorsal valve (X4). 



5. Ventral valve (Walcott fig. 2a) (X 6). 



6. Smaller dorsal valve (X 3)- 



7. Ventral valve (X 5)- 



Iphidella maladensis Walcott 20 



8. Ventral valve (Walcott fig. 2) (X4)- 



9. Lectotype dorsal valve (Walcott fig. 2e) (X 3). 



10. Another dorsal valve (Walcott fig. 2d) (X 5)- 



Acrotreta sulcata Walcott 21 



11. Exterior ventral valve (X 9)- 



12. Dorsal valve (X6). 



13. Ventral valve (X6). 



14. Holotype ventral valve (Walcott fig. 5) (X9)- 



Acrotreta eucharis, new species 22 



15. Dorsal valve (X7)- 



16. Dorsal valve (X 5)- 



17. Exterior ventral valve (X6). 



18. Ventral valve (X8). 



