PLATE XXIV. 
. Pedicle groove. 
. Median septum. 
. Visceral cavity. 
. Main vascular sinus. 
a. Central lateral Space of area. 
a’. Outer lateral space of area. 
. Flexure line of area. 
. Central muscle scar. 
. Anterior Jateral muscle scar. 
adutd 
i=7 
Pay 
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LINGULELLA NANNO (Walcott) (p. 521). 
Ficures 1 and la. Ventral valves, preserving natural form and convexity, from Locality 16, Middle Cambrian 
limestones in Blountsville Valley, Blount County, Alabama. U.S. Nat. Mus. Cat. Nos. 27328a and 
27328b, respectively. Figure la represents the type specimen. 
1b and 1c. Dorsal valves associated with the specimens represented by figures 1 and la. U.S. Nat. Mus. 
Cat. Nos. 27328¢ and 27328d, respectively. 
id. Unusually large and convex dorsal valve from Locality 91, Middle Cambrian limestone at Cedar 
Bluff, Cherokee County, Alabama. U.S. Nat. Mus. Cat. No. 57005a. 
LINGULELLA LEOS (Walcott) (p. 513). 
Fieure 2. Partly exfoliated ventral valve. U.S. Nat. Mus. Cat. No. 27323a. 
2a. Cast of the interior of a ventral valve, the type specimen. U.S. Nat. Mus. Cat. No. 27323b. 
2b and 2c. Casts of interior of two dorsal valves. 2c is strongly convex and unusually narrow and elongate. 
U.S. Nat. Mus. Cat. Nos. 27323c and 27323d, respectively. 
The specimens represented are all from Locality 96, Upper Cambrian limestone, 1.5 miles south of Rome, Floyd 
County, Georgia. 
LINGULELLA HELENA (Walcott) (p. 506). 
Figure 3. Exterior of a slightly distorted ventral valve from Locality 302s, Middle Cambrian siliceous shale 1.5 miles 
south of Helena, Lewis and Clark County, Montana. U.S. Nat. Mus. Cat. No. 27320a. 
3a and 3b. Casts in siliceous shale of the interior of two ventral valves that differ in outline, from the locality 
represented by figure 3. U.S. Nat. Mus. Cat. Nos. 27320b and 27320c, respectively. Figure 3a 
represents the type specimen. 
3c. Cast of the interior of a dorsal valve showing area, from the locality represented by figure 3. U.S. Nat. 
Mus. Cat. No. 27320d. 
3d. Small ventral valve doubtfully referred to the species, from Locality 30a, Middle Cambrian shale in 
Big Cottonwood Canyon, near Salt Lake City, Utah. U.S. Nat. Mus. Cat. No. 51819a. 
LInGULeLia puBIA (Walcott) (p. 494). 
Ficure 4. Cast of interior of ventral valve, the type specimen, associated with Obolus ( Westonia) ella at Locality 31, 
Middle Cambrian shales at Pioche, Nevada. U.S. Nat. Mus. Cat. No. 2731]4a. 
4a. Cast of interior of dorsal valve on same piece of shale with the specimen represented by figure 4. U.S. 
Nat. Mus. Cat. No. 27314b. 
LINGULELLA AaRGUTA (Walcott) (p. 478). 
Figure 5. Perfect ventral valve, the type, from Locality 318f, Upper Cambrian limestone at Schellbourne, Schell 
Creek Range, Nevada. U.S. Nat. Mus. Cat. No. 273805a. Drawn from specimen represented by 
White [1877, Pl. III, fig. 2a] as Lingula? manticula. 
5a. Dorsal valve that is doubtfully referred to this species from Locality 318a, Middle Cambrian limestone 
at Schellbourne, Nevada. U.S. Nat. Mus. Cat. No. 51845a. : 
5b. Partly exfoliated dorsal valve from Locality 10y, Middle Cambrian Marjum limestone, near Marjum 
Pass, House Range, Utah. U.S. Nat. Mus. Cat. No. 58303. 
86 
