Il8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL.53 



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Micromitra (Paterina) stuarti, new species 58 



Figs. 8 and 8a. Top and posterior views of type specimen of ventral 

 valve from the Middle Cambrian limestones of the Ute 

 formation, Blacksmith Fork Canyon, Cache County, Utah. 

 U. S. National Museum Catalogue No. 514850. 



Obolus smithi, new species 62 



Fig. 9. Exterior of a slightly distorted dorsal valve. U. S. National 

 Museum Catalogue No. 51611a. 

 pa. Cast of the interior of a dorsal valve. U. S. National Mu- 

 seum Catalogue No. 5161 1&. 



The specimens represented by Figs. 9 and ga are from 

 Lower Cambrian Montevallo shale, .125 mile (.20 km.) 

 northeast of Helena, Shelby County, Alabama. 



Obolus parvus, new species 61 



Fig. 10. Exterior of ventral valve. U. S. National Museum Cata- 

 logue No. 514000. 

 loa. Exterior of dorsal valve. U. S. National Museum Cata- 

 logue No. 51400&. 



The specimens represented by Figs. 10 and loa are from 

 a drift block of Lower Cambrian shale on the slope of Mt. 

 Bosworth, British Columbia. 



Obolus membranaceous, new species 61 



Fig. II. Type specimen showing cast of ventral valve flattened in the 

 Middle Cambrian shales of the Eldon formation, north- 

 west of Mt. Bosworth, British Columbia. U. S. National 

 Museum Catalogue No. 53674a. 



Obolus ( Westonia) elongatus, new species 68 



Fig. 12. Type specimen showing cast of ventral valve from Middle 

 Ordovician shales in Wasatch Canyon, north of Brigham, 

 Box Elder County, Utah. U. S. National Museum Cata- 

 logue No. 51722a. 



Obolus ( Westonia) notchensis, new species 69 



Fig. 13. Type specimen showing exterior of partially exfoliated ven- 

 tral valve from Lower Ordovician limestones on Notch 

 Peak, House Range, Millard County, Utah. U. S. Na- 

 tional Museum Catalogue No. 51731a. 



Obolus ( Westonia) dartoni, new species 67 



Fig. 14. Type specimen showing exterior of ventral valve from Mid- 

 dle Cambrian sandstones west of Garfield Peak, Natrona 

 County, Wyoming. U. S. National Museum Catalogue 

 No. 51683a. 



Obolus (Fordinia) gilberti, new species 65 



Fig. 15. Top and side views of a ventral valve. U. S. National Mu- 

 seum Catalogue No. 519460. 

 15a. Interior of a ventral valve. U. S. National Museum Cata- 

 logue No. 51946^. 



The specimens represented by figures 15 and 15a are 

 from Middle Cambrian limestones of the Marjum forma- 

 tion, south of Marjum Pass, House Range, Millard County, 

 Utah. 



