PLATE LXXVI. 
el. Cardinal sear. vs. Main vascular sinus. 
{p. False pedicle groove. x. Foraminal aperture. 
s. Median septum or ridge. x’. Cast of foramimal tube. 
v. Visceral area. x’’. Cast of apical callosity. 
ACROTRETA INFLATA (Matthew) (p. 690). 
Fieures | and 1’. Top and side views of an unusually well-preserved ventral valve, showing radiating lines on 
inner lamellee of the shell. Locality 2f£, Middle Cambrian sandstones of Division 1b1 of Matthew’s 
[1895, p. 108] Protolenus zone, Hanford Brook, St. John County, New Brunswick. U.S. Nat. Mus. 
Cat. No. 35276a. 
Ja and la’. Top and side views of an elevated ventral valve associated with the specimen represented by 
figure 1. U.S. Nat. Mus. Cat. No. 35276b. 
1b and 1b’. Top and side views of a ventral valve associated with the specimen represented by figure 1, 
with the apex broken off so as to show the cast of the large apical callosity and the base of the small 
foraminal tube. U.S. Nat. Mus. Cat. No. 35276c. 
le, 1c’, and 1c’. Top, side, and back views of a partly exfoliated ventral valve associated with the 
specimen represented by figure 1, showing cast of the large cardinal muscle scars and apical callosity. 
U.S. Nat. Mus. Cat. No. 35276d. 
1d and 1d’. Top and side views of a ventral valve in which the false area slopes forward. Middle Cam- 
brian sandstones of Division 1b1 (the general horizon of localities 2f and 2g) on Hanford Brook, 
St. John County, New Brunswick. University of Toronto, Canada. (See figure lg for back view.) 
le and le’. Top and side views of a broad ventral valve from Locality 2g, Middle Cambrian, in sandstones 
of Division 1b1 of Matthew on Hanford Brook, St. John County, New Brunswick, preserving the 
foraminal aperture.’ U.S. Nat. Mus. Cat. No. 35276e. 
Hf, 1f, and 1%”. Top, side, and back views of a specimen with a relatively small apical callosity and 
vertical false area. Middle Cambrian sandstones of Division 1b1 (the general horizon of localities 
2f and 2g) on Hanford Brook, St. John County, New Brunswick. University of Toronto, Canada. 
lg. Back view of specimen represented by figure 1d, with upper portion restored from another specimen. 
th. Cast of an elongate dorsal valve associated with the shell represented by figure 1. U.S. Nat. Mus. 
Cat. No. 352768. 
li. Partly exfoliated dorsal valve associated with the specimen represented by figure le. U.S. Nat. 
Mus. Cat. No. 35276g. 
1k and 1k’. Top and back views of cast of dorsal valve associated with the specimen represented by 
figure le, showing large cardinal scars and strong median ridge. U.S. Nat. Mus. Cat. No. 35276h. 
2. Ventral valve from the same general horizon as that of localities 2fand 2g, Middle Cambrian sandstones of 
Division 1b1 on Hanford Brook, St. John County, New Brunswick. University of Toronto, Canada. 
Drawn from the type specimen of the species; it was figured by Matthew [1886, Pl. V, figs. 7 and 7a] 
as Lingulella? inflata. 
2a. Ventral valve associated with the specimen represented by figure 2. University of Toronto, Canada. 
Specimen figured by Matthew [1895a, Pl. V, figs. 4a-c] as Lingulella? inflata ovalis. 
ACROTHYRA PROAVIA (Matthew) (p. 717). 
[Pl. LXXYV, fig. 3.] 
Ficure 3. Slender, elongate ventral valve from Locality 131, Middle Cambrian shaly sandstones of E3a of Matthew’s 
Etcheminian, Dugald Brook, Cape Breton, Nova Scotia. University of Toronto, Canada. This 
specimen was first illustrated by Matthew [1901b, fig. 1, p. 303] as Acrothyra proavia prima. 
3a and 3a’. Top and side views of a ventral valve. U.S. Nat. Mus. Cat. No. 52052a. 
3b. A broader form of the ventral valve than that shown by figure 3. U.S. Nat. Mus. Cat. No. 52052b. 
3c. A ventral valve associated with specimen represented by figure 3. University of Toronto, Canada. 
3d, 3d’, and 3d’. Top, back, and side views of a ventral valve with the apex broken off. Labeled ‘‘A. 
proavia var.;” it is probably the variety ‘‘crassa” Matthew. University of Toronto, Canada. Hori- 
zon and locality unknown. 
3e and 3e’. Top and side views of a broad ventral valve; this probably represents the form for which 
Matthew proposed the variety crassa. U.S. Nat. Mus. Cat. No. 52052c. 
ce 
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