78 
ALLISON SPECIES 
Inoceramus cf. lundbreckensis n. sp. 
Plate XVII, figure 1 
Only one fragmental specimen of the left valve has been collected. 
Large, apparently oblique, and higher than long. Gently convex, a 
shallow sulcus above the postumbonal slope and a low ridge along the 
postero-dorsal submargin. Surface ornamented with numerous, even, 
narrow, concentric ribs and also, at intervals, low concentric undulations, 
most pronounced where they cross the postumbonal slope and bearing, 
where they meet the low ridge along the postero-dorsal submargin, irregular 
nodes. There are also narrow radiating ribs of moderate relief on the 
central part of the shell. 
It is very close to Inoceramus lundbreckensis n. sp. and allowing for a 
little variation might be placed within that species. It differs chiefly in 
having low, distant undulations rather than distant, wide concentric ribs, 
in the lesser convexity, and the somewhat greater relief of the radiating 
ribs. 
Horizon and Locality. In the lower part of the Allison formation on 
Gulch creek, about 100 feet above base of section there exposed. 
Type. National Museum of Canada; Cat. No. 9038. 
Ostrea saxitoniana n. sp. 
( Saxitonia , the Rocky Mountain country) 
Plate XIV, figures 8, 9 
Chiefly specimens of the right? valve are known. Of average size, 
much higher than long, moderately convex. The centre of the shell is 
conspicuously arched from the umbones to the middle of the ventral 
margin and the anterior and posterior marginal areas are flattened. The 
adductor scar in the interior of the shell is a little posterior to the middle. 
A small specimen shows a mould of a narrow, shallow, ligamental pit and 
the beaks apparently curved posteriorly; on either side, in the dorsal 
part, the inner border is crenulated. The above descriptions apply to 
most of the specimens and to the typical species, but one fairly large 
specimen of the right? valve is only moderately convex. 
A small fragmental specimen may be the other valve of this species. 
It is about as convex as the shells designated above as right? valves. 
Height 31 mm., length 22 mm. 
Horizon and Locality. In the lower part of the Allison formation on 
Gulch creek and about 185 feet above base of section there exposed. 
Types . National Museum of Canada; holotype, Cat. No. 9039; 
paratype, Cat. No. 9039a. 
