25 
and part of the beak, which is straight in the young shells, 
but slightly curved in the old ones. 
This species, as well as the last, is found at Highgate, 
and I do not know that it occurs elsewhere. It differs 
from the last in being longer in proportion to its width, and 
more regular in its form; it has but one row of little projec- 
tions on a less angular ridge, below which the shell is most 
gibbous. The striz are mostly simple. The lips are nearly 
the same, but the right one is slighty toothed all along 
the inner edge; see the front and back views, right and left 
hand middle figures. The lower figures are from parts of 
larger and more mature shells, one showing the outer lip 
on the surface of the shell, which continues beyond it; thus 
it appears that this animal, like other shelly animals, may, 
after perfecting its shell, leave the former lip and continue 
its growth; it has some of the top of the newest lip left, 
joining the left lip, which is extravagantly spread over the 
body of the shell. The other figure is an amber coloured 
Carbonate of Lime cast of this species, -it is distinguished 
from the cast of C. carinata by its regular surface wanting 
the nodose ridges. 
These shells vary somewhat, so that some approach more 
than others to the last described. J am uncertain therefore 
whether it be correct to consider them as distinct species, 
and I am inclined to believe that Lamarcke supposes them 
to be only varieties. Jn either case the figures may prove 
useful. 
