76 
45 degrees to the ventral margin; posterior margin very short and abruptly 
rounded, forming the end of the cuneate extension. Umbones and beaks 
pronounced, approximate. In front of the beaks and above the anterior 
shield-shaped callus is a concave area. Surface less convex toward 
postero-dorsal and posterior margins. Anterior callus shield-shaped and 
rises prominently above remainder of shell. Posterior gape and anterior 
gape narrow. A very narrow sulcus, sloping backward, extends from the 
beak to a little in front of the middle of the ventral margin. Surface 
covered with low, small, angular costae which, anteriorly, where they curve 
upward, behind the callus, become closely crowded fine striae; the anterior 
callus apparently smooth. The dorsal umbonal accessory plate sub- 
circular and divided by a medium very narrow groove. Corresponding to 
the exterior sulcus is a narrow internal ridge from the beak to a little in 
front of the middle of the ventral margin. The specimens are preserved 
in silicified w r ood. 
The species name is given for James McEvoy, Geologist. 
Length 11 -5 mm., height 6 mm. 
Horizon and Locality . In the Colorado shale of the Crowsnest River 
section west of the Blairmore sheet, about 1,360 feet above the base of the 
section there exposed. 
Types . National Museum of Canada; holotype, Cat. No. 9035; 
paratypes, Cat, Nos. 9035a, b. 
Pholadomya nitanae n. sp. 
Plate XIV, figure 7 
Only one specimen is known, consisting of both the right and left 
valves. In the left valve the hingeline is long, although a little shorter 
than the total length of the shell; the anterior and ventral margins are 
rounded; the posterior margin is obliquely truncate above. Moderately 
convex, the umbones prominent and the beaks rising considerably above 
the hingeline and incurved ; beaks situated about one-third from the anterior 
end. About 17 narrow costae radiate from the beak and are weak or absent 
m the antero-dorsal angle. A few concentric costae of the same relief and 
some of lesser size cut across the radiating costae. The right valve is not 
so convex as the left and the umbo is smaller. 
Nitana was the wife of Onesta, an Indian chief. 
Length, 34*5 mm., height, 25 mm. 
Horizon and Locality . In the Colorado shale of the Crowsnest River 
section west of the Blairmore sheet, about 30 feet above the section there 
exposed. 
Type. National Museum of Canada; holotype, Cat. No. 9036. 
