186 PALEOZOIC PALEONTOLOGY. 
‘CYCLONEMA MONTREALENSIS Bill. 
Plate XII., Fig. 33. 
1865. Cyclonema montrealensis Bill., Pal. Foss., vol. I., p. 30, fig. 
28, Pp. 29. 
Description.—Shell with the height and width about equal, the 
diameter of full-grown individuals being from 20 to 30 mm. Apical 
angle about 90°. Volutions about four, rather rapidly enlarging and 
strongly convex. Suture distinct. Aperture subcircular. Surface 
marked by strong, revolving lines, .5 to 1 mm. apart, and by much 
finer, oblique, transverse lines. 
Remarks.—All the specimens of this species which have been studied 
are more or less crushed, so that the amount of variation of the apical 
angle cannot be determined, though it is probably never less than 90°. 
The apex of all the specimens seen is imperfect, so that there’ may 
have been one or two additional volutions in the perfect shells. 
HOLOPEA SYMMETRICA Hall. 
Plate XII., Figs. 26-27. 
1847. Holopea symmetrica Hall, Pal. N. Y., vol. L., p. 170, pl. 37, 
fig. 1. 
Description.—Shell attaining a height of 12 mm. to 15 mm., the 
width about equal to or less than the height. Volutions three or four, 
rounded, ventricose, increasing gradually from the apex; the aperture 
nearly circular, slightly oblique. Surface marked by fine, raised, 
more or less crowded lines of growth, which are sometimes slightly 
fasciculate in their arrangement. 
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