PLATE LIX. 197 
ACROTHELE YORKENSIS Walcott (p. 661). 
Fieure 4. Exterior of the type specimen, a distorted, broken ventral valve, from Locality 48d, Middle Cambrian shales 
in railroad cut at York, Pennsylvania. U.S. Nat. Mus. Cat. No. 5203la. Copied from Walcott 
[1908d, Pl. IX, fig. 10]. 
4a and 4b. Compressed, exfoliated dorsal valves associated with the specimen represented by figure 4. U.S. 
; Nat. Mus. Cat. Nos. 52031b and 52031c, respectively. 
ACROTHELE PANDERI Walcott (p. 651). 
Fiaures 5 and 5’. Exterior and side views of a ventral valve, the type specimen, from Locality 4v, Lower Cambrian 
shales on Gordon Creek, Ovando quadrangle, Montana. U.S. Nat. Mus. Cat. No. 52003a. 
5a. Exterior of ventral valve associated with the shell represented by figure 4. U.S. Nat. Mus. Cat. No. 
52003b. 
5b. Exterior of ventral valve from Locality 5j, Lower Cambrian shales 6 miles west-northwest of Scapegoat 
Mountain, Coopers Lake quadrangle, Montana. U.S. Nat. Mus. Cat. No. 52002a. 
5c. Partly exfoliated dorsal valve associated with the shell represented by figure 5b. U.S. Nat. Mus. Cat. 
No. 52002b. 
