PLATE I. 



Cidaris from the Lias. 

 Fig. 



1 a. Cidaris Edwards ii, Wright, p. 26. Natural size, and restored to its globular form. 



b. One inter-ambulacral plate, and a portion of an ambulacral area, with the poriferous 



zones ; magnified three diameters. 



c. A view in profile of one of the primary tubercles, magnified three times. 



d. A secondary spine, from an ambulacral area. 



e. The same, magnified five times. 



/. One of the primary spines, magnified three times. 



g. Lateral view of a jaw and tooth, magnified one and a half times. This specimen 

 shows a portion of the buccal membrane, with the spines which clothed the same. 



Cidaris from the Inferior Oolite. 



2 a. Cidaris Bouchardii, Wright, p. 36. Shell natural size, showing the base. 



b. Ditto, a side view of the same. 



c. One inter-ambulacral plate, and a portion of an ambulacral area, with the poriferous 



zones ; magnified four diameters. 



3 a. Cidaris Wrightii, Desor, p. 39. Test the natural size, showing the upper surface. 



b. Test the natural size, showing a lateral view. 



c. One inter-ambulacral plate, and a portion of an ambulacral area, with the poriferous 



zones ; magnified four times. 



d. A primary spine, supposed to belong to C. Wrightii. 



e. Another spine, referred to the same species. 



/. A portion of the same, magnified four diameters. 



4 a. Cidaris Fowleri, Wright, p. 32. Natural size, showing the base of the test, with 



the jaws in situ. 



b. Lateral view of the same, showing the projection of the jaws. 



c. One inter-ambulacral plate, and a portion of an ambulacral area, with the poriferous 



zones ; magnified three diameters. 



d. Portion of a spine attached to the test, this specimen belongs to the Museum of 



Geology, Jermyn Street. 



5 a. Diplocidaris Wrightii, Desor, p. 58. Fragment of a spine. 



b. The same, magnified two and a half diameters. 



c. nov. sp. 



