PLATE VI. 



ClDAKIS SCEPTRIFERA, Mmitell, 1822. 



From the White Chalk. 



Fia. 

 1 a. Upper surface of the test, natural size. This magnificent specimen belongs to the 



British Museum. P. 54. 



b. Under surface of the same, natural size. 



» 



c. Lateral view of the same, natural size. 



d. Inter-ambulacral plate, ambulacra, and poriferous zones, magnified three dia- 



meters. 



e. The uppermost plate of an inter-ambulacral column, showing the curious nuli- 



mentary tubercles, and areola thereon, magnified two diameters. 

 /. The uppermost plate of the adjoining column, magnified two diameters. 



a. A portion of the apical disc, consisting of one ovarial, two ocular plates, and three 



anal plates, magnified two diameters. The entire disc is seen in sittt, in 

 fig. 1 a. 

 h. Three anal plates, magnified two diameters. 



2. Test with spines, natural size. This specimen belongs to the Museum of the 

 Royal School of Mines. 



3 a. Spine, type form, natural size. 



b. The upper part of the stem, magnified three diameters. 



c. The stellate form of the terminal extremity, magnified three diameters. 



4 a. Spine, type form, natural size. 



6. The head, neck, and milled ring of the same, magnified three diameters. 



5 a, h. Another spine, natural size. 



6. A variety. Specimens 3, 4, 5, and 6, belong to the British Museum. 



