TO GEOLOGY. 161 
England. Eleven have been described by Sowerby, Phil- 
lips and Mantell, one as low as the Inferior Oolite. The 
highest are in the London Clay, where five species have 
been observed by Mr Sowerby. M. Deshayes gives eight 
for the Tertiary. No species has heretofore been observed 
in this country to my knowledge. 
FAMILY PURPURIFERA. 
GENUS MONOCEROS. Lamarck. 
JM. pyruloides. Plate 5. Fig. 166. 
Description. Shell turbinate, inflated, transversely and 
indistinctly striate above and below; substance of the 
shell thick; transverse furrow linear, with indistinct 
angular points; spire short; suture small; whorls five, 
convex ; umbilicus rather large; mouth ovate, narrow ; 
columella thickened ; outer lip sharp. 
Length .7, Breadth .5, of an inch. 
Observations. 'This species is.remarkable for its turbi- 
nate form. The superior part of the mouth is much 
thickened. It may be objected to, that this and the two 
following species should be placed in the genus Monoceros, 
as none of the specimens observed have the seat of the 
horn perfect. This part is therefore not described. I 
am satisfied nevertheless as to the genus; for the groove 
Vv 
