in length has somewhat the aspect of a Thracia. If the relation
of parts be the same as in that genus, then the umbo is slightly
posterior to the middle and is recurved. It seems possible, how-
ever, that this is J. de C. Sowerby's " Unio " gaulteri 1 , which
was described from the Hastings Beds near Tunbridge Wells, a
species about which little is known. Small specimens of the
shell from Penshurst have a very different shape from the large
elongated one mentioned above. The same doubtful form has
been found near Groombridge and there are specimens of it,
preserved as external moulds, in the Museum of Practical
Geology.
Pttrbeck Beds.
A general sketch of the distribution of the fossils observed to
occur in the Purbeck rocks passed through in this boring, based
upon observations made at the locality, has already been given in
the previous part of this work. The list which here follows, with
the depths at which the species occur, has reference only to a
series of specimens brought away for examination and can give
no complete picture of the real distribution.
