TO GEOLOGY. 103 
Observations. This species differs from those which pre- 
cede it, in having transverse striz. The whorls are inflated, 
while the others are flat. 
P. sulcata. Plate 4. Fig. 84. 
Description. Shell conical, largely and transversely sul- 
cate above; substance of the shell thin; apex obtuse ; suture 
furrowed ; whorls five, flattened ; mouth subelliptical, one 
third the length of the shell; columella flattened at the 
base; margin thickened above. 
Length .1, Breadth 1-20th, of an inch. 
The smaller figure is of the size of nature. 
Observations. A very minute species, remarkable for its 
large furrows, which become obsolete on the lower part of 
the whorls. It differs from striata in being less elevated, 
as well as in having furrows. 
P. umbilicata. Plate 4. Fig. 85. 
Description. Shell elevated above, rounded below, sub- 
carinate, polished; substance of the shell thin; apex acute ; 
suture linear; umbilicus large; whorls nine, flattened ; 
mouth subovate, acutely angular above, one fifth the length 
of the shell ; columella incurved at base ; margin entire. 
Length .2, Breadth .1, of an inch. 
The smaller figure is of the size of nature. 
Observations. 'This smooth and polished species differs 
from the above in being umbilicate. Its umbilicus is wide, 
