PLATE XXXVI. 
c. Trapezoidal area, including central, middle p. Pedicle groove. 
lateral, and outside lateral muscle scars. s. Median septum. 
g. Umbonal muscle scar. v. Visceral cavity. 
h. Central muscle sear. ; vs. Main vascular sinus. 
i. Transmedian muscle scar. ivs. Lateral branches of vascular system. 
j. Anterior lateral muscle scar. pvs. Peripheral branches of vascular system. 
k. Middle lateral muscle scar. x. Heart-shaped cavity. 
1. Outside lateral muscle scar. 
OBOLUS SELWYNI (Matthew) (p. 413). 
(Pl. XX XVII, figs. 1, 1a-f.] 
Figure 1. Interior of a dorsal valve, showing a portion of the visceral area and adjoining parts; also the striation of 
one of the inner layers of the shell. University of Toronto, Canada. Redrawn (with fig. 1c) from the 
specimens on which Matthew [1903] based the diagrammatic figures in the left-hand figure on page 
117 and figures la and Ic of Plate VII of his paper. 
Ja. Exfoliated ventral valve, showing the visceral area and adjoining portions of the interior of the shell. 
University of Toronto, Canada. ° 
1b. Side outline of specimen represented by figure la. 
lc. Interior of a ventral valve, longitudinally compressed, which emphasizes the main vascular sinuses and, 
the lateral branches of the vascular system. University of Toronto, Canada. Redrawn (with fig. 1) 
from the specimens on which Matthew [1903] based the diagrammatic figures in the left-hand figure 
on page 117 and figures la and lc of Plate VII of his paper. 
ld. Interior of a dorsal valve, showing portions of the vascular system. University of Toronto, Canada. 
le, 1f, and lg. Interior of dorsal valves, showing variation in position of the central and anterior lateral muscle 
scars. University of Toronto, Canada. 
lh. Dorsal valve longitudinally compressed, giving it a very broad form. This may be compared with figures 
le and lf of Plate XX XVII. University of Toronto, Canada. 
2. Cast of interior of a ventral valve, broadened by compression. University of Toronto, Canada. Specimen 
figured by Matthew [1902c, Pl. I, fig. 4b] as Obolus xquiputeis. 
2a. Cast of interior of a dorsal valve. University of Toronto, Canada. Specimen figured by Matthew [1902c, 
Pl. I, fig. 4d] as Obolus xquiputeis. 
2b. Cast of the interior of a dorsal valve. University of Toronto, Canada. 
The specimens represented are all from Locality 307d, Middle Cambrian sandy limestone of Division E2a? on Youngs 
Point, near George River Station, Cape Breton, Nova Scotia. 
LINGULELLA uPiIs (Walcott) (p. 538). 
Ficures 3.and 3’. Top and side views of partly exfoliated ventral valve, the type specimen, from Locality 14i, Upper 
Cambrian limestone 1 mile west of Cherokee, San Saba County, Texas. U.S. Nat. Mus. Cat. No. 
51804a. 
3a. Fragmentary dorsal valve associated with the ventral valve represented by figure 3. U.S. Nat. Mus. 
Cat. No. 51804b. 
LINGULELLA BELLA (Walcott) (p. 481). 
[Pl. XIX, figs. 2, 2a-q.] 
Ficure 4. Slab of arenaceous shale with numerous well-preserved shells from Locality 114b, Lower Ordovician sand- 
stone 1 mile north of Lance Cove, Great Belle Island, Conception Bay, Newfoundland. U. $. Nat. 
Mus. Cat. No. 27308n. 
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