20 
coarser, and more apt to pass into a callous tooth-like pro- 
jection over the umbilicus. These are found abundantly in 
the dark clay at Highgate, from the size of the upper figure 
down to the size of a small pea, varying somewhat in the 
spreading of the pillar lip, and having sometimes the lines 
of growth more worn and distinct ; the outer lip being thinner 
or thicker according to its state of maturity. The middle 
figure shews the left lip more spread, thinner, and partly 
worn away on the body of the shell, and the projection half 
covering the umbilicus. I have named it as above, from its 
resemblance to Nerita Glaucina. The cast is sometimes 
found in clay, coated with dark Pyrites, or hollow, lined 
with crystallized iridescent Pyrites. 
NATICA similis. 
TAB. V. 
Spec. Cuar. Shell rather rhomboidal; spire short, 
umbilicus divided by a spiral proj jeu mouth 
slightly angular above. 
Two middle figures. 
eee 
Spine small, of three or four nearly flat volutions, giving a 
rhomboidal contour to the whole shell, the umbilicus double, 
or divided by a transverse spiral projection, terminating at 
the inner or left lip, forming an obtuse lobe, from which the 
lip afterwards spreads on the shell, and terminates abruptly 
against the curve of the upper part of the outer lip, a little 
like Nerita pallidula. I could not help being very much 
pleased with the extraordinary similitude of this specimen 
and a specimen of a recent shell, bearing the name of Nerita 
rufa, (see Mont. Test. Brit. Sup. tab. 30, p. 150) which it 
agrees with, excepting in colour and size, being smaller, 
