PLATE XCIX. 
a. Cardinal area. f. Cast of dental sockets. 
b. Dental sockets. pe. Pseudocruralium. 
d. Delthyrium. sp. Free spondylium or cast of it. 
d’. Cast of didnetor scars. t. Teeth. 
PROTORTHIS BILLINGSI (Hartt) (p. 739). 
Figure 1. Cast of ventral valve from a natural mold, in which the area is compressed and crowded backward. U.S. 
Nat. Mus. Cat. No. 52424a. 
la. Natural cast of compressed ventral valve. U.S. Nat. Mus. Cat. No. 52424b. 
1b, 1b’, and 1d, 1d’. Top and back views of natural casts of compressed ventral valves in which the area is 
shown. 1d’ shows the cast of the spondylium. U.S. Nat. Mus. Cat. Nos. 52424c and 52424d, 
respectively. 
lc. Natural cast of a compressed ventral valve (locality unknown). University of Toronto, Canada. 
le and 1f. Natural casts of compressed dorsal valves. U. S. Nat. Mus. Cat. Nos. 52424e and 52424f, 
respectively. 
lg. Natural cast of the outer surface of a small dorsal valve. U.S. Nat. Mus. Cat. No. 52424¢. 
With the exception of figure 1c the specimens represented are all from Locality 3b, Middle Cambrian shale, head 
of Seeley Street, St. John, St. John County, New Brunswick. None of them has been figured before. 
PROTORTHIS QUACOENSIS (Matthew) (p. 742). 
Fictre 2. Exterior of a compressed ventral valve. 
2a. A minute ventral valve referred to this species. 
2b. Top, side, and posterior views of the cast of an uncompressed ventral valve, showing elevation, cardinal 
area, and deltidium. Type specimen, figured by Matthew [1886, Pl. V, figs. 20b and a 
2c. An uncompressed dorsal valve, with posterior and side view in outline. 
2d. Dorsal valve distorted by compression and movement in the shale. 
2e. Top and posterior views of the cast of a dorsal valve. Specimen figured by Matthew [1886, Pl. V, figs. 
20 and 20a). 
The specimens represented are from Division le of Matthew’s Etcheminian, but Matthew does not state [1886, 
pp. 44 or 82] whether they are from Porters Brook (Locality 301m) or Portland (Locality 301g), St. John County, 
New Brunswick. They are all in the collections of the University of Toronto, Canada. 
PROTORTHIS LATOURENSIS (Matthew) (p. 741). 
Figures 3 and 3’. Mold of interior of a dorsal? valve, with side outline (locality unknown). University of Toronto, 
Canada. 
3a. Matrix in fine shale of the exterior of a ventral valve from Locality 308h, Middle Cambrian shales of 
Division 1cl at Portland, St. John, New Brunswick. U.S. Nat. Mus. Cat. No. 18185a. 
3b. Posterior view of mold of a ventral valve showing mold of spondylium (locality unknown). University 
of Toronto, Canada. 
3c. Posterior view of the mold of a ventral valve (locality unknown). University of Toronto, Canada. 
3d. Matrix of exterior of a dorsal valve from Locality 301w, Middle Cambrian shales of Division 1c2 of Matthew 
at Portland, St. John, New Brunswick. U.S. Nat. Mus. Cat. No. 18168a. 
Figures 3, 3b, and 3c were drawn from specimens in Matthew’s original material, but none of the specimens 
represented by Matthew in figures 18, 18a-c [1886, Pl. V] is redrawn in this monograph. 
PROTORTHIS HELENA Walcott (p. 740). 
Fiatre 4. Cast of ventral valve, the type specimen, from Locality 2u, Middle Cambrian shale on south side of Long 
Island, Kennebecasis Bay, St. John County, New Brunswick. U.S. Nat. Mus. Cat. No. 52427a 
da and 4b. Side and back views of the specimen represented by figure 4. 
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