Note 5 — Chapter XIII

There are only two of these exclusively west-coast shells,—Trochus umbilicatus and Pecten niveus. As neither of them has yet been detected in any Tertiary formation, they are in all probability shells of comparatively recent origin, that came into existence in some western centre of creation; whereas specimens of Trochus magus and Nassa reticulata, which occasionally occur on the eastern coasts of the kingdom, I have also found in a Pleistocene deposit. Thus the more widely-spread shells seem to be also the shells of more ancient standing.