41.8 
T1I13 GEOLOGIST. 
this respect in tlie slightest degree, and the same exceptional cases 
as rarely occur among the true crinoids. 
If we examine the echinoderms from the Oolite, the Chalk, or the 
Tertiary beds, we find them one and all reclining on tlieir broadest 
diameters, in fact, obeying the laws of gi\avitation, but which appears 
to have been overcome in Palaechinus by some countervailing 
influence, which resisting force was probably an elongated column. ^ 
It must be understood that I do not positively maintain tliat 
Palajchinus was attached to the sea- bed by a jointed flexible column, 
but that one evidence in favour of such an addition to its character 
is strong, if not convincing. 
GEMS OF PRIVATE COLLECTIONS. 
UNIO AND PALUDIN^. 
From the Wealden Beds of Kent, in the collection of 
Mr. W. Harris, F.G.S., of Charing. 
The Sussex Marble, or Bethersden Marble, as it is indifferently 
termed according to its occurrence in Kent or Sussex, is found also 
in Surrey, near the foot of Leith Hill. It occurs in thin coui-ses of 
variable thickness and extent, but seldom presenting a bed one foot 
thick, in the weald clay. 
It is made up chiefly of the shells of Paludince, whole or in frag- 
ments. Occasionally the shells retain their form, as in the specimen 
figured, and weather out on exposm-e ; but often only their casts are 
exposed, the matrix being calcareous matter derived from the disinte- 
gration of the shells. The shells of Uniones also occur ; rarely, as 
in the specimen figured, retaining this form ; more often as casts. 
Cyprid^ also occur in abundance ; but the small size of the tiny shells 
or valves of these little entomostraca cause them to be overlooked. 
The Cijpridea Valdensis is the common species. The animal matter 
of the Paludinte appears to be often preserved in this marble, and 
gives to the polished sections the dark grey and black markings so 
characteristic of the stone. Pui'beck marble is a similar stone, older 
than that of the weald clay, and formed of a Paludina of smaller size. 
The Paludina of the Sussex marble is scarcely to be distinguished 
from that of the existing rivers and ponds, namely, the P. vivlpora ; 
but Sowerby points out that it has a thicker shell, and is somewhat 
turbo-like in aspect ; and has termed it P. f uviorimi, (Min. Conch., 
pi. 31. fig. 1 ; vol. i, p. 77, and vol. vi. ^. 192). A larger form from 
