Figure 1. 
1 
i) 
Ib. 
Hes 
1d. 
lr. 
1s. 
PGA Ee xan: 
a. Central lateral space of area. h. Central muscle scar. 
a’. Outer lateral space of area. j. Anterior lateral muscle scar. 
c. Trapezoidal area, including central, middle p. Pedicle groove. 
lateral, and outside lateral muscle scars. vs. Main vascular sinus. 
{. Flexure line of area. x. Heart-shaped cavity. 
LINGULELLA (LINGULEPIS) EXIGUA (Matthew) (p. 551). 
[Pl]. XXXII, figs. 4 and 4a] 
Narrow acuminate ventral valve from Locality 10t, Middle Cambrian sandstone on McLean Brook, near 
Marion Bridge, Cape Breton, Nova Scotia. U.S. Nat. Mus. Cat. No. 34766a. 
. Slightly broader form of ventral valve than that represented by figure 1, but associated with it. U.S. 
Nat. Mus. Cat. No. 34766b. 
Broader form of ventral valve than that represented by figure la, but associated with it. Specimens 
showing gradations of form between figures la and 1b occur in the collections. U.S. Nat. Mus. Cat. 
No. 34766c. 
Still broader form of ventral valve intermediate between specimens represented by figures 1b and If. 
Associated with the specimens represented by figures 1, la~b. U.S. Nat. Mus. Cat. No. 34766e. 
Small ventral valve with slightly rounded instead of straight or incurved cardinal slopes, from Locality 
3i, Middle Cambrian sandstone on McLean Brook, 1.5 miles west of Marion Bridge, Cape Breton, 
Nova Scotia. U.S. Nat. Mus. Cat. No. 3476la. 
. Small narrow ventral valve laterally compressed, associated with the specimen represented by figure 1d. 
U.S. Nat. Mus. Cat. No. 34761b. 
. Large, partly exfoliated ventral valve associated with the specimen represented by figure ld. U. 8. 
Nat. Mus. Cat. No. 34761c. é 
. Elongate and attenuate ventral valve, showing cast of the interior surface, also a portion of the outer 
surface. It is associated with the shell represented in figure 1d. U.S. Nat. Mus. Cat. No. 34761d. 
. Small ventral valve with outer shell on posterior portion. It is associated with the shell represented in 
figureld. U.S. Nat. Mus. Cat. No. 3476le. 
. Small, partly exfoliated ventral valve compressed and flattened in the arenaceous shale. It isassociated 
with the shell represented in figure ld. U.S. Nat. Mus. Cat. No. 34761f. 
j. Cast of interior of a broad form of ventral valve somewhat like specimen represented by figure 1c in outline. 
It is associated with the specimens represented by figures 1, la-c. U.S. Nat. Mus. Cat. No. 34766d. 
. Small dorsal valve with strong median sinus. It is associated with the shell represented in figure 1d. 
U.S. Nat. Mus. Cat. No. 34761g. 
. Cast of the interior of a dorsal valve that hasa few pustulesonit. It isassociated with the shell represented 
in figure ld. U.S. Nat. Mus. Cat. No. 34761h. 
. Cast of part of the interior of a well-preserved dorsal valve. It is associated with the shell represented in 
figure 1d. U.S. Nat. Mus. Cat. No. 347611. 
. Fragment of arenaceous shale from Locality 10t (see fig. 1, above), with 2 group of small shells upon it. 
Natural size. U.S. Nat. Mus. Cat. No. 34766f. 
. Cast of the interior of ventral valve, showing cast of pits and the strong ridges of the main vascular canals, 
from Locality 3i, Middle Cambrian sandstone on McLean Brook, 1.5 miles west of Marion Bridge, 
Cape Breton, Nova Scotia. U.S. Nat. Mus. Cat. No. 34761). 
. Part of the interior of a ventral valve associated with the specimen represented by figure lo, showing the 
strong ridges beneath the main vascular sinuses. U.S. Nat. Mus. Cat. No. 34761k. 
. Cast of interior of a ventral valve, showing heart-shaped area (x), trapezoidal area (c), and cast of vascular 
canal ridges (vs). Locality 10s, Middle Cambrian sandstone on McLean Brook, near Marion Bridge, 
Cape Breton, Nova Scotia. U.S. Nat. Mus. Cat. No. 52468b. 
Cast of interior of a dorsal valve associated with the specimen represented by figure 1q, showing area, 
visceral cavity, and portion of vascular canal ridges. U.S. Nat. Mus. Cat. No. 52468c. Another 
specimen (Cat. No. 34761r, from Locality 3i) was used to restore certain portions of this figure. 
Cast of the interior of a dorsal valve associated with the specimen represented by figure lo, showing strongly 
marked visceral and vascular ridges. U.S. Nat. Mus. Cat. No. 34761 1. 
142 
