PLATE CI. 
a. Cardinal area. ye ad’. Cast of umbonal cavity. 
b. Dental sockets. 6 dl. Delthyrium. 
c. Crura. 
e. Adductor sears. 
d. Deltidium. ¢ 
aay j. Cardinal process. 
ek 
NisusiA (JAMESELLA) PERPASTA (Pompeckj) (p. 735). 
Figures 1 and la. Exterior and side views of a strongly costate ventral valve from Locality 345k, Lower Cambrian 
sandstones at Slapnicky Mlyn, near Skrej, Bohemia. U.S. Nat. Mus. Cat. No. 52302a. 
1b and le. Casts of exterior of ventral valves associated with the specimen represented by figures 1 and la. 
U.S. Nat. Mus. Cat. Nos. 52302b and 52302c, respectively. 
1d, 1d’, and 1d’. Summit, back, and side views of cast of exterior of ventral valve from Locality 345i, Lower 
Cambrian conglomeratic sandstones of the Kamennd& hirka, near Tejfovik, Bohemia. U. S. Nat. 
Mus. Cat. No. 52301a. 
le. Cast of a dorsal valve associated with the specimen represented by figures ] and la. U.S. Nat. Mus. Cat. 
No. 52302d. 
1f. Cast of a dorsal valve associated with the specimen represented by figure 1d. U.S. Nat. Mus. Cat. No. 
52301b. 
lg. Front view of cast of ventral valve from Locality $46i, see figure 1d. Copied from Pompeckj [1896b, Pl. 
XV, fig. 16d]. , 
\ 
th. Cast of dorsal valve associated with the specimen represented by figures 1 and la. U.S. Nat. Mus. Cat. 
No. 52302e. 
NisusiA (JAMESELLA) PERPASTA SUBQUADRATA (Pompeckj) (p. 736). 
Figure 2. Cast of ventral valve from Locality 345i, Lower Cambrian conglomeratic sandstones of the Kamenna hirka, 
near Tejfovik, Bohemia. U.S. Nat. Mus. Cat. No. 52304a. 
2a. Cast of ventral valve from the locality represented by figure 2. Type specimen, copied from Pompeckj 
[1896b, Pl. XV, fig. 19a]. 
2b. Cast of dorsal valve from the locality represented by figure 2. Copied from Pompeckj [1896b, Pl. XV, 
fig. 20a]. 
NisusiA (JAMESELLA) PERPASTA MACRA (Pompeckj) (p. 736). 
Figure 3. Cast of ventral valve doubtfully referred to this variety from Locality 3451, Lower Cambrian conglomeratic 
sandstones of the Kamenna hirka, near Tejiovik, Bohemia. U.S. Nat. Mus. Cat. No. 52303a. 
3a. Cast of dorsal valve from the locality represented by figure 3. Type specimen, copied from Pompeckj 
[1896b, Pl. XV, fig. 14]. 
Nisust (JAMESELLA) KUTHANI (Pompeckj) (p. 732). 
Figures 4 and 4’. Cast of exterior of ventral valve, with back view. U.S. Nat. Mus. Cat. No. 26643a. 
da, 4a’, and 4a’’. Summit, back, and side views of a cast of a ventral valve. U.S. Nat. Mus. Cat. No. 
26643b. 
4b. Cast of dorsal valve. U.S. Nat. Mus. Cat. No. 26643c. 
The specimens represented are all from Locality 345i, Lower Cambrian conglomeratic sandstones of the Kamenn4 
hirka, near Tejfovik, Bohemia. 
Nisusta (JAMESELLA) ERECTA Walcott (p. 732). 
Fieures 5, 5a, and 5b. Ventral, dorsal, and back views of the type specimen, which consists of the two valves united. 
In figure 5a the umbo has been restored; on figure 5 the ribs are too much rounded. From Locality 
313g, Middle Cambrian limestone at the south end of the Timpahute Range in the Groom mining dis- 
trict, Nevada. U.S. Nat. Mus. Cat. No. 52299a. 
338 
