PLATE LXII. 
c. Area. j. Anterior lateral muscle scar. 
el. Cardinal scar. k. Middle lateral muscle scar. 
F’. Cast of foraminal tube. 1. Outside lateral muscle scar: 
h. Central muscle sear. ys. Vascular sinus. 
ACROTHELE AVIA Matthew (p. 634). 
(Pl. LXI, figs. 7, 7a-b.] 
Ficure 1. Top view of a typical form of the ventral valve from Locality 13n’, Middle Cambrian sandstones of Division 
B3e of Matthew’s section, Dugald Brook, Cape Breton, Nova Scotia. U.S. Nat. Mus. Cat. No. 56598a. 
la. Top view of a ventral valve nearly circular in outline from Locality 13d’’, Middle Cambrian sandstones 10 
feet below top of Division E2a of Matthew’s section, Dugald Brook, Cape Breton, Nova Scotia. U.S. 
Nat. Mus. Cat. No. 56601a. 
1b. Laterally compressed ventral valve from Locality 181’, Middle Cambrian sandstones of Deion E3a on 
Dugald Brook, Cape Breton, Nova Scotia. U.S. Nat. Mus. Cat. No. 51970a. 
lc. Partly exfoliated ventral valve from Locality 18m, Middle Cambrian sandstones of Division E3f on 
Gillis Brook, Cape Breton, Nova Scotia. U.S. Nat. Mus. Cat. No. 56596a. The surface of this 
specimen is enlarged in figure 1}. 
1d. Exfoliated ventral valve (locality unknown). » University of Toronto, Canada. 
le. Fragment of the interior of a ventral valve associated with the specimen represented by figure 1. U.S. 
Nat. Mus. Cat. No. 56598b. 
1f. Cast of interior of dorsal valve, from Locality 18n, Middle Cambrian sandstones of Division E3f of Mat- 
thew’s section, Dugald Brook, Cape Breton, Nova Scotia. U.S. Nat. Mus. Cat. No. 56597a. 
1g. Interior of dorsal valve associated with the specimen represented by figure 1c. U.S. Nat. Mus. Cat. No. 
56596b. 
th. Interior of a compressed dorsal valve placed with the specimens from Locality 18m; the exact locality is, 
however, unknown. U.S. Nat. Mus. Cat. No. 56596c. 
li. Exfoliated dorsal valve from Locality 344b, Middle Cambrian shales of Division E3d of Matthew’s 
Etcheminian, Dugald Brook, Cape Breton, Nova Scotia. University of Toronto, Canada. Specimen 
fizured by Matthew [1902b, Pl. XVII, fig. 2b]. 
1j. Enlargement of a portion of the surface of the specimen represented by figure 1c. 
1k. Posterior portion of a ventral valve showing the apex. Associated with the specimen represented by 
figure Ib. U.S. Nat. Mus. Cat. No. 51970b. 
ACROTHELE PRIMA (Matthew) (p. 653). 
[Pl. LXI, figs. 6, 6a-b.] 
Ficure 2. Partly exfoliated ventral valve from Locality 13t, Middle Cambrian shaly sandstones of Division E1b on 
Dugald Brook, Cape Breton, Nova Scotia. U.S. Nat. Mus. Cat. No. 52009a. 
ACROTHELE PROLES Matthew (p. 654). 
Ficure 3. Exterior of a slightly compressed ventral valve from Locality 18m, Middle Cambrian shaly sandstones of 
Division E3f on Gillis Brook, Cape Breton, Nova Scotia. U.S. Nat. Mus. Cat. No. 52011a. 
34. Portion of a dorsal valve associated with the specimen represented by figure 3. U. S. Nat. Mus. Cat. 
No. 52011b. 
3b. Interior of a fragmentary ventral valve associated with the specimen represented by figure 3. U.S. Nat. 
Mus. Cat. No. 52011c. 
3c. Interior of a small slightly distorted ventral valve associated with the specimen represented by figure 3. 
U.S. Nat. Mus. Cat. No. 52011d. 
3d. Partly exfoliated dorsal valve associated with the specimen represented by figure 3. U.S. Nat. Mus. Cat. 
No. 52011e. 
3e. Partly exfoliated dorsal valve, showing vascular markings on the inner layers of the shell. Locality 
13n, Middle Cambrian shaly sandstones of Division E3f on Dugald Brook, Cape Breton, Nova Scotia. 
U.S. Nat. Mus. Cat. No. 52012a. 
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