PLATE XII. 



From the White Chalk. 



Fig. 1 a. Test and spines of Cidaris intermedia, Wiltsli., natural size. Collection of 

 Rev. Thomas Wiltshire, F.G.S. (P. 69). 

 b. Spine belonging to the tubercle, the third from the peristome, magnified. 



Fig. 2. Spine of Cidaris hirudo (?), magnified. 



Fig. 4. Unusual form of spine, probably belongmg to (J. scepirifera, magnified. Col- 

 lection of Rev. Thomas Wiltshire, F.G.S. 



From the Lower Chalk. 



Fig. 3 a. Spine of Cidaris dissimilis, Forb., natural size. Collection of Rev. Thomas 



Wiltshire, F.G.S. (P. 46 ) 

 h. Head and spine of same magnified. 

 Fig. 5. Spine of Cidaris pleracantha, Agass., natural size. Collection of J. R. 



Capron, Esq., F.G.S. (P. 67.) 



From the Tipper Greeensand. 



Fig. 6. Spine of C. Bixoni, natural size. Collection of Rev. Thomas Wiltshire, 

 F.G.S. (P. 67.) 



From the Red Chalk. 



Figs. 7,8, 9. Spines of Cidaris, natural size, from Hunstanton. Cabinet of Rev. 



Thomas Wiltshire, F.G.S. (P. 79.) 

 Fig. 10 a. Spines of Cidaris, natural size, from Speeton. (P. 79.) 

 Fig. b. The same, magnified. 



