PLATE LV. 
a. Central lateral space of area. pe. Cast of pedicle opening. 
i. Transmedian muscle scar. s. Median septum. 
j. Anterior lateral muscle scar. v. Visceral cavity. 
1. Outside lateral scar. vs. Main vascular sinus. 
p. Pedicle groove. x. Heart-shaped cavity 
OBOLELLA ATLANTICA Walcott (p. 589). 
(Text fig. 51, p. 590.] 
Figure 1. Exterior of an unusually convex, elongate ventral valve. Locality 50, Lower Cambrian siliceous shale, 
Smith Sound, Trinity Bay, Newfoundland. U.S. Nat. Mus. Cat. No. 51948a. 
la. Cast in siliceous shale of the exterior of a ventral valve, showing surface characters of the shell. Same 
locality as specimen represented by figure 1. U.S. Nat. Mus. Cat. No. 51948b. 
lb. Exterior of a small ventral? valve. Locality 41a, Lower Cambrian limestone beneath Topsail Head, 
Conception Bay, Newfoundland. U.S. Nat. Mus. Cat. No. 56957a. 
le. Exterior of small dorsal valve, associated with specimen represented by figure 1b. U.S. Nat. Mus. Cat. 
No. 56957b. 
1d. A slightly distorted dorsal valve from Locality 50, Lower Cambrian siliceous shale, Smith Sound, New- 
foundland. U.S. Nat. Mus. Cat. No. 51948c. 
le. Interior of a ventral valve associated with the shell represented by figure 1d. The pedicle furrow is too 
strong in the figure. On the specimen it is indicated by a slightly depressed line on each side of 
what is usually the pedicle furrow. This specimen is also figured in a slightly different position in 
text figure 51, p.590. U.S. Nat. Mus. Cat. No. 51948d. : 
1f and lg. Casts of the interior of ventral valves associated with the shell represented by figure 1d. U.S. 
Nat. Mus. Cat. Nos. 51948e and 51948f, respectively. 
lh. Top and side view of cast of the interior of a ventral valve, the type specimen, from Locality 41, Lower 
Cambrian decomposed limestone, from Manuels Brook, Conception Bay, Newfoundland. U.S. Nat. 
Mus. Cat. No. 18322a. 
li. Cast of the interior of a dorsal valve, associated with specimen represented by figure lh. U.S. Nat. Mus. 
Cat. No. 18322b. 
OBOLELLA (GLYPTIAS) FAVOSA (Linnarsson) (p. 600). 
Ficure 2. Exterior and side view of ventral valve. U.S. Nat. Mus. Cat. No. 35264a. 
2a. Exterior and side view of dorsal valve. U.S. Nat. Mus. Cat. No. 35264b. 
2b. Cast of the interior of ventral valve that retains a portion of the shell. U.S. Nat. Mus. Cat. No. 35264c. 
2c. Cast of the interior of small dorsal valve. U.S. Nat. Mus. Cat. No. 35264d. 
2d. Outer surface of shell greatly enlarged. U.S. Nat. Mus. Cat. No. 35264e. 
The specimens represented by figures 2, 2a-d are from Locality 309c, Lower Cambrian sandstone at Billingen, 
Province of Skaraborg, Sweden. 
OBOLELLA MOBERGI Walcott (p. 597). 
Figures 3 and 3a. Exterior and side view of ventral valve, drawn from a cast taken in a natural mold in sandstone. 
Original in the collection of the Geological Museum, Lund, Sweden; cast in the United States National 
Museum (Cat. No. 35261a). 
3b. Posterior view of specimen represented by figure 3, showing area and cast of pedicle slit. 
3c. Cast in fine sandstone of interior of ventral valve, the type specimen. U.S. Nat. Mus. Cat. No. 35261b. 
3d. Enlargement of a natural cast of a portion of the outer surface. U.S. Nat. Mus. Cat. No. 35261c. 
3e. Cast of the interior of a dorsal valve. U.S. Nat. Mus. Cat. No. 35261d. 
3f. Cast of the interior of a dorsal valve. U.S. Nat. Mus. Cat. No. 3526le. 
The specimens represented are all from Locality 321s, Lower Cambrian sandstone at Sularp, near Lund, Province 
of Malméhus, Sweden. 
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