318 THE MEDALS OF CREATION. Cuap. IX. 
Diapema. Lign. 101, fig. 4, 6.—The shell in this genus 
is of a more depressed form than in Cidaris; there are two 
rows of large tubercles, which are crenulated and perforated, 
on the ambulacra as well as on the interambulacral spaces. 
The spines are slender and annulated. Mr. Woodward 
remarks that the common Chalk species referred by authors 
to this genus, belong to the sub-genus Cyphosoma of Mt? 
Agassiz, in which the tubercles are imperforate. There are 
nearly fifty fossil species known, and they range from the 
Lias to the Chalk. The recent analogues inhabit the seas of 
warm regions. 
Ecuinus.—The shells of the genus Echinus resemble 
those of Cidaris in their general structure, but the tubercles 
are imperforate. More than twenty fossil species are de- 
scribed, from the Oolite and Chalk. 
SALENIA.—In the greensand pits near Faringdon, in Berk- 
shire, which abound in fossil sponges and other poriferz 
ante, p. 228), there are immense numbers of a small elegant — 
5) is) 
Turban Echinite, which belongs to the genus thus named by 
the eminent zoologist, Dr. J. E. Gray, of the British Museum. 
The collector will easily recognize these sea-urchins by the 
plated summit. The shell has five ovarian and five in- 
terovarian plates, and an eleventh or odd one. The tu-_ 
bercles are crenulated. The common species at Faringdon is — 
S. petalifera, of Desmarest. Two species of this genus, viz. 
S. scutigera and S. stellulata, from near Warminster, are 
figured in Pict. Atlas, pl. liu. fig. 12, 13. 
Cidarites of New Zealand.—Detached plates and spines 
of sea-urchins, belonging to the family Cidaritide, have been 
discovered by Mr. Walter Mantell, in the Ototara limestone 
of New Zealand ; which is a fawn-coloured stone, composed 
of foraminifere, like the Chalk, and containing terebratule, 
corals, and teeth of sharks.* 
* Geol. Journal, vol. vi. p. 319. 
