PLATE X. 



CiDARis HiRUDO, Soriyuet, LS50. 



From the White Chalk. 



Fig. 1 a. Test the natural size, with spines attached^ in the collection of Professor 

 Tennant, F.G.S. (P. 64.) 



I b. Primary spine of the same, magnified twice. 

 Fig. 2. Lateral view of another specimen belonging to the British Museum. 

 Fig. 3 a. Upper surface of a small specimen belonging to the British Museum. 



3 h. Under surface of a small specimen belonging to the British Museum. 



3 c. Lateral view of a small specimen belonging to the British Museum. 



3 d. Interambulacral plate, ambulacral area zones of the same, maguitied three 



times. 



Fig. 4. Primary spine magnified twice, in the cabinet of the Rev. T. Wiltshire, F.G.S. 



Fig. 5. Primary spine magnified twice, in the cabinet of the Rev. T. Wiltshire, F.G.S. 



Fig. 6. Primary spine magnified twice, in the cabinet of the Rev. T. Wiltshire, F.G.S. 



