13 
Representations also, of this species, are seen in most of the works of 
the foreign ory otologists. 
In the figures given by Drs. Plot and Lister, considerable difference 
is observable. The form of the one is rather orbicular and depressed, 
and of the other somewhat conoidal : in the one are no papillae, whilst 
in the other they are well preserved. Leske, who has remarked the 
difference very correctly, explains it, in part, by considering the latter 
as a silicious cast : a circumstance which fully accounts for the absence 
o the papillae ; but the difference of their form remains unaccounted 
for. An examination, however, of the fossils figured Plate I. Fig. 9 
and 11, will, I think, show that this difference is only to be ex- 
plained, b) supposing the two fossils to be of two distinct species, or 
at least varieties. 
In the echinite from Oxfordshire, of a globose form, Plate I. Fig. 9, 
the narrow strip of area, edged by the ambulacra, is formed by four 
rows of small and equal sized granular tubercles ; whilst in the other, 
Plate I. Fig. 11, from Kent, these areolae are wider; and, except 
towards their superior and inferior extremities, are composed of six 
rows of granular tubercles, which are large in the external rows, and 
dimmish as they approach the centre. Its papilla, though perforated 
m the apex, are not crenulated at the base. The much greater space 
of granulated area between the papilla, and the conoidal form of the 
S ? ’ a so help to constitute a difference so great, as to lead to the 
opinion that it should be considered as a distinct species. If this 
should be admitted, the species might be distinguished as cidaris 
papillata conoidea. 
The echinite from Wiltshire, Plate I. Fig. 6, beautiful from its 
original formation, and estimable as a fossil, from its state of pre- 
servation being such, that even somewhat of the original colour of the 
shell is still to be perceived, partakes so much of the characters of 
. and papillata , as to render it difficult to determine 
with which it should be arranged. Like the former, its less area 
