PLATE LII. I 7(Al 
DICELLOMUS PECTENOIDES (Whitfield) (p. 575) 
[Text figs. 48A-B, p. 575.] 
Fravure 6. A transverse, partly exfoliated ventral valve from Locality 355b, Middle Cambrian sandstone on Castle 
} Creek, Black Hills, South Dakota. U.S. Nat. Mus. Cat. No. 24592a. Specimen figured by Whit- 
field [1880, Pl. II, fig. 18] as Obolus ? pectenoides. This may be the type specimen, but it can not 
be identified with any of Whitfield’s figures [1875, unnumbered plate, figs. 1-3]. 
6a. Partly exfoliated dorsal valve associated with the shell represented by figure 6. U.S. Nat. Mus. Cat. 
No. 24592b. Specimen figured by Whitfield [1880, Pl. II, fig. 19] as Obolus ? pectenoides 
6b. Cast of interior of a ventral valve from Locality 164, Middle Cambrian sandstone near Deadwood, Black 
Hills, South Dakota. U.S. Nat. Mus. Cat. No. 5191la. 
6c. Cast of interior of a dorsal valve associated with the shell represented by figure 6b. U.S. Nat. Mus. Cat. 
No. 51911b. 
DiceLLomus sp. undt. Walcott (p. 578). 
Ficures 7 and 7a. Exterior and side views of a dorsal valve, from Locality 3101, Middle Cambrian at Andrarum, 
Province of Christianstad, Sweden. U.S. Nat. Mus. Cat. No. 58304. 
