32 
Pedicle valve nearly flat. Pedicle opening situated in the line of the 
longer axis of the shell, and extending from the centre of the valve half-way 
to the posterior margin; externally this has the form of a groove, the 
anterior part of which is much depressed below the general surface of the 
valve; posteriorly it becomes very shallow; internally it forms an elongate 
ridge highest and widest anteriorly. The internal surface is marked by 
about three faint growth lines in the space of 1 mm. ; externally, besides the 
growth lines, which here were apparently elevated into ridges, there are 
very faint and numerous radiating lines. 
Brachial valve moderately convex, subconical, its apex situated 
excentrically about two-fifths the total length of the valve from the pos- 
terior margin. From the apex the surface is most convex anteriorly; 
laterally and posteriorly it descends to the margins with greater abruptness. 
Surface markings unknown. 
Remarks. This Minnewanka form is preserved in a fine-grained 
quartzite and lacks some desired details. There are three pedicle valves 
and three more poorly preserved brachial valves; of the former two are 
views of the interior and one of the exterior. These specimens show a 
certain similarity to 0. missouriensis Shumard from the Pennsylvanian 
of the Mississippi valley, but this species is smaller, with apex of brachial 
valve nearer the margin and with greater convexity ; the concentric ridges are 
also more numerous. O.utahensis (Meek) has a much higher brachial valve. 
Specific name given because of its occurrence in a quartzite. 
Locality and Horizon. In the Minnewanka region in the Permian of 
section 1-14 (c). 
Genus, Leptaena Dalman 
Leptaena analoga (Phillips) 
The following are some references to this Mississippian form of Lep- 
taena rhomboidalis (Wilckens). 
1836. Producta analoga Phillips, Geol. Yorkshire, vol. 2, p. 215, Pl. 7, 
fig. 10; Strophomena rhomboidalis var. analoga Davidson, 1859, 
Brit. Foss. Brach., vol. 2, p. 119, PI. 28, figs. 1-2; 5. rhomboidalis 
WRite, 1874, Prelim. Rept., Inv. Foss., p. 17; White, 1877, U.S. 
Geog. Surv. W. 100th Mer., vol. 4, p. 85, PI. 5, fig. 5; Hall and 
Whitfield, 1877, U.S. Geol. Expl. 40th Par., voL 4, p. 253, PI. 4, 
fig. 4; Herrick, 1888, Bull. Sci. Lab. Denison Univ., vol. 4, PI. 9, 
fig. 6; Herrick, 1889, Am. Geol., vol. 3, PI. 4, fig. 6; Leptaena 
rhomboidalis Hall and Clarke, 1892, Int. to Study of Brach., pt. 1, 
PI. 13, fig. 9; Hall and Clarke, 1892, Pal. N.Y., vol. 8, pt. 1, Pl. 8, 
figs. 30-31, Pl. 20, fig. 24; Plectambonites rhomboidalis Keyes, 1894, 
Mo. Geol. Surv., vol. 5, p. 70, Pl. 39, fig. 6; Strophomena rhom- 
boidalis Herrick, 1895, Geol. Surv., Ohio, vol. 7, Pl. 20, fig. 6; 
Leptaena rhomboidalis Girty, 1899, Mon. U.S. Geol. Surv., vol. 
32, p. 525; Girty, 1904, Prof. Paper, U.S. Geol. Surv., No. 21, 
p. 48, Pl. 10, fig. 3; Weller, 1909, Bull. Geol. Soc., Am., vol. 20, 
p. 292, Pl. 12, figs. 2-3; L. analoga Weller, 1914, Geol. Surv., Mon. 
1, p. 49, Pl. 2, figs. 1-10. 
