71 
Locality. Marl beds, McKay lake, Colton lake, and else- 
where in the Ottawa valley. 
One of the most common shells in these deposits. It is 
readily recognized by the characteristic bell or campanulate 
expansion. Marl specimens as a rule show little variation. 
Planorbis altissimus Baker 
Plate VIII, figures 18a-18f 
Shell small, dextral, rounded; surface shining, lines of 
growth fine, oblique, slightly elevated; apex slightly below the 
general level of the whorls; whorls four, rapidly enlarging, 
periphery rounded; in some cases sub-carina ted, spire slightly 
depressed or flat showing all the volutions, sutures deeply im- 
pressed; base concave, with wide, shallow umbilicus showing 
all the volutions; aperture oblique ovate, nearly on same plane 
as last whorl; peristome, thin, slightly expanded, upper edge 
produced over lower margin unthickened by callus. Termina- 
tion of peristome connected by thin callus on parietal wall. 
H. 1-25 W. 4-1 A.H. 1*15 A. W. 1-35 
Locality. Marl bed, McKay, Colton, and Mink lakes. 
This is one of the most common of the small Planorbes in these 
deposits, though not as common as Amnicola porata. It can be 
readily distinguished from P. exacuous Say by the absence of 
the sharp peripheral carina of the latter. From P. defiectus and 
P. hirsutus, it can be differentiated by its smooth shell and much 
smaller size. 
* Planorbis defiectus Say 
Plate VII, figures 13a-13b 
Shell small, dextral, flat. Lines of growth numerous, fine, 
oblique; apex below level of the whorls; whorls four to five and 
a half, rapidly expanding, periphery sub-carinate, all of the whorls 
in the same plane except the first which is depressed; whorls 
flattened above, slightly rounded below, last whorl deflected 
downward; aperture oblique suboval; peristome thin, acute; 
callus on the parietal wall; umbilicus wide, shallow, exhibiting 
all the volutions. 
