18 
contract at the margin, and thus continue to where they meet in the 
centre of the lower part of the shell, which is rather excavated and 
grooved where the ambulacra pass. The whole of the surface of the 
shell is thickly beset with granular tubercula, the largest of which 
are surrounded by small circular risings. This species is figured by 
Plott, Tab. ii. 9, 10, and is found chiefly at Tangley, Fulbrook, and 
Burford, in Oxfordshire : they are also found in Gloucestershire. 
Plott’s engraving is copied by Lister; and Lhwydd, n. 9/T, as well 
as Morton, p. 233, both describe this fossil. 
It is of this fossil that Dr- Plott informs us, Hist, of Oxfordshire, 
p. 91, that the centre of these rays being never placed on the top of 
the stone, but always inclining to one side, as that at the bottom does 
to the other, the axis lying obliquely to the horizon of the stone, gave 
occasion to a learned society of virtuosi, that during the late usurpa- 
tion lived obscurely at Tangley, by consent, to term it the polar 
stone ; since, by clapping two of them together, they made up a 
globe, with meridians descending to the horizon, and the pole elevated, 
very nearly corresponding to the real elevation of the pole of the 
place where the stones are found. 
The Cl. hemisphcericus, Lesk. Tab. xliii. Fig. i. taken from Lang, 
p. 119, does not appear to belong to this section ; even Cl. quinquela- 
hiatus , Lesk. Tab. xli. Fig. 3, taken from Walch, PI. e. hi. Fig. 4, 
is in such a state as will hardly allow of determining its real species. 
Cl. Conoideus, Lesk. Tab. xliii. Fig. 3, appears to be a rare petri- 
faction, and but little known. It seems, however, to agree in every 
respect with Echinus magnus, Aldrov. Mus. Met. p. 456. 
