PLATE CIII. d47 
SyntTRopHia ALATA Walcott (p. 799). 
Figures 3, 3’, and 3”. Cast of the interior of a ventral valve, with side and back views. U.S. Nat. Mus. Cat. 
No. 52466a. 
3a. Exterior of ventral valve, the type specimen. U.S. Nat. Mus. Cat. No. 52466b. 
3b and 3c. Casts of interior of ventral valves. U.S. Nat. Mus. Cat. Nos. 52466c and 52466d, respectively. 
3d. Partial cast of the interior of a dorsal valve. U.S. Nat. Mus. Cat. No. 52466f. 
The specimens represented by figures 3, 3a-d are all from Locality 69, Upper Cambrian limestone near Honey 
Creek, Burnet County, Texas. 
SYNTROPHIA RoTUNDATA Walcott (p. 804). 
Fiaures 4, 4’; 4a; and 4b, 4b’. Top and side views of three dorsal valves varying in form and in strength of median 
fold. U.S. Nat. Mus. Cat. Nos. 524938a, 52493b, and 52493c, respectively. 
4a’. View of area and hinge line of ventral valve. U.S. Nat. Mus. Cat. No. 52493h. 
4c and 4c’. Top and side views of ventral valve, the type specimen. U.S. Nat. Mus. Cat. No. 52493d. 
Another specimen (Cat. No. 52493g) was used to restore certain portions of this figure. 
U.S. Nat. Mus. 
4d. Section across the umbo of a ventral valve, showing outline of section of spondylium. 
Cat. No. 524938e. 
4e. Section of shell and spondylium of dorsal valve. U.S. Nat. Mus. Cat. No. 52493f. 
The specimens represented by figures 4, 4a-e are all from Locality 14k, Upper Cambrian limestone on Wolf | 
Creek, 15 miles (24.2 km.) west-southwest of Sheridan, Bighorn Mountains, Wyoming. 
