PLATE LVII. 
el. Cardinal scars. s. Median septum. 
F. Foramen. v. Visceral area. 
F’. Cast of pedicle tube. vs. Vascular sinus. 
ACROTHELE BOHEMICA (Barrande) (p. 639). 
Fieures land l’. Top and side views of ventral valve, the type specimen, from Locality 345¢e, Middle Cambrian 
shales at Mleschitz, Bohemia. Copied from Barrande [1879b, Pl. CII, figs. viz: 1A and 1B], where 
they are labeled Obolus ? bohemicus. 
Ja and la’. Top and side views of a dorsal valve associated with the ventral valve represented by figure 1. 
Copied from Barrande [1879b, Pl. CII, figs. vi: 2A and 2B], where they are labeled Obolus ? bohemicus. 
1b. Ventral valve from Locality 345, Middle Cambrian shales on the Dlouha Hora, above the brook of Sbirov, 
near Skrej, Bohemia. Copied from Pompeckj [1896b, Pl. XIV, fig. 8b]. 
1c. Dorsal valve from the locality represented by figure 1b. Copied from Pompeckj [1896b, Pl. XIV, 
fig. 11]. 
1d. Interior of dorsal valve from the locality represented by figure 1b. Copied from Pompeckj [1896b, Pl. 
XIV, fig. 10b]. 
ACROTHELE MACULATA (Salter) (p. 647). 
[Pl. LVIL, fig. 2.] 
Ficure 2. Exterior of dorsal valve. 
2a. Exterior of dorsal valve. oa r, Tae 
2b. Cast of the interior of a dorsal valve, the type specimen. 
Figures 2, 2a-b are copied from Davidson [1868, Pl. XVI, figs. 1-3]; the same figures being copied by Davidson in 
his later work [1871, Pl. L, figs. 18.19, and 21]. Davidson states that the specimens are from Porth-y-rhaw, St. Davids, 
and from Gwynfynydd and Camlan, North Wales. 
ACROTHELE BELLAPUNCTATA Walcott (p. 636). 
Figure 3..Exterior of partly exfoliated ventral valve, the type specimen. U. §. Nat. Mus. Cat. No. 51972a. 
'' Copied from Walcott [1908d, Pl. VIII, fig. 9]. 
3a. Exterior of partly exfoliated dorsal valve. U.S. Nat. Mus. Cat. No. 51972b. : 
3b. Surface of outer layer enlarged 15 diameters. U.§. Nat. Mus. Cat. No. 51972c. A portion of the surface 
represented by figure 3b was illustrated by Walcott [1908d, Pl. VIII, fig. 9’] as the surface of the 
specimen represented by figure 3; it is, however, taken from another specimen. 
The specimens represented are all from Locality 8v, Lower Cambrian shales at Ringsaker, near Lake Mjésen, 
Province of Hedemarken, Norway. 
BorsFORDIA GRANULATA (Redlich) (p. 605). 
Ficure 4. Cast of exterior of an almost perfect specimen of the transversely oval form of the ventral valve. U.S. 
Nat. Mus. Cat. No. 52046s. 
4a. Exterior of a longitudinally elongate oval form of the ventral valve. U.S. Nat. Mus. Cat. No. 52046a. 
4b. Exterior of a transversely oval dorsal valve, preserving the two small sharp tubercles at the apex. U.S. 
Nat. Mus. Cat. No. 52046b. 
4c. Posterior portion of a ventral valve, showing the pedicle aperture. U.S. Nat. Mus. Cat. No. 52046c. 
4d. Posterior portion of a ventral valve, showing a crescentiform tubercle on each side of and a small tubercle 
just back of the depression at the apex; the pedicle aperture is just back of the posterior tubercle 
and in fact appears to come up through it. U.S. Nat. Mus. Cat. No. 52046d. 
4e. Exterior view of elongate form of dorsal valve. U.S. Nat. Mus. Cat. No. 52046e. 
4f and 4f’. Exterior and side view of a ventral valve intermediate in outline between the specimens repre- 
sented by figures 4 and 4a. U.S. Nat. Mus. Cat. No. 52046f. 
4g. Cast of interior of ventral valve. U.S. Nat. Mus. Cat. No. 52046g. 
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