PLATE LXV. 219 
ACROTRETA IDAHOENSIS ALTA Walcott (p. 689). 
Ficurss 4, 4’, and 4’. Top, side, and back views of a ventral valve from Locality 15d, Upper Cambrian limestone near 
Cave Spring, Fish Spring Range, Utah. U.S. Nat. Mus. Cat. No. 52099a. 
4a, da’, and 4a/’. Top, side, and back views of a ventral valve from Locality 58, Middle Cambrian shaly lime- 
stone in either New York or Secret Canyon, Eureka district, Nevada. U.S. Nat. Mus. Cat. No. 
35273a. Type specimen, figured by Walcott [1884b, Pl. I, fig. la]. 
4b. Dorsal valve associated with the specimen represented by figure 4. U.S. Nat. Mus. Cat. No. 52099b. 
ACROTRETA IDAHOENSIS SULCATA Walcott (p. 690). 
Fieurss 5, 5’, and 5’. Top, side, and back views of a ventral valve, the type specimen, with the apex broken off. 
From Locality 322a, Middle Cambrian Langston limestone near Paris, Idaho. U.S. Nat. Mus. Cat. 
No. 35275a. f 
ACROTRETA EMMONSI Walcott (p. 684). 
Fiaure 6. Cast of the interior of a dorsal valve, the type specimen, from Locality 35a, Lower Cambrian limestone on 
Bald Mountain, Washington County, New York, showing vascular markings and muscle scars. 
U.S. Nat. Mus. Cat. No. 52087a. 
