PLATE III. 



Cidaris from the Bed and Grey Chalk. 

 CiDARis VESICULOSA, Gold/uss, 1820. 



Fro7n the Grey Chalk. 



Fig. 



1 a. Under surface of a large test, Grey Chalk, Dover, natural size. British Museum. 



P. 41. 



b. The under surface of the same test, natural size. 



c. A lateral view of the same test, natural size. 



d. One inter-ambulacral plate, with a portion of the ambulacra and poriferous zones, 



magnified three times. 



e. A primary tubercle, magnified. 



3 a. Test of Cidaris vesiculosa (?), from the Red Chalk, iinder surface, natural size. 

 In the collection of C. B. Rose, Esq., P.G.S. 



b. Upper surface of the same test, natural size. 



4. Inter-ambulacral spine from the Red Chalk. In the collection of C. B. Rose, Esq., 

 F.G.S. 



5 a. Ditto ditto ditto. 



f). Portion of the same, magnified three times. 



Cidaris dissimilis, Forbes, 1854. 

 From the Lower Chalk. 



2 a. Upper surface of the test, natural size. In the collection of Rev. T. Wiltshire, F.G.S. 



P. 46. 



h. Under surface of the same test, natm-al size. 



c. Lateral view of the same test, natural size. 



d. Inter-ambidacral plate, ambulacra, and poriferous zones, magnified three times. 



e. A single tubercle, magnified. 



/. Portion of an inter-ambulacral spine, magnified. 

 g. An ambulacral spine, greatly magnified. 



