PLATE VIII. 



Pseudodiademas from the Coralline Oolite. 

 Fig. 



1 a. Pseudodiadema HEMisPHiERicuM, Agassiz, p. 127. Upper surface of the test, natu- 



ral size. 



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



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



d. The half of a portion of an inter-ambulacral area, and a portion of an ambulacral 



area, with the poriferous zones ; magnified twice. 



e. Apical disc, magnified two diameters. 



/. Base of an ambulacral area, showing the trigeminal pores in this region. 



2 a. Pseudodiadema mamillanum, Boemer, p. 132. Upper surface of the test, natural 



size. 



b. Under surface of the test, natural size. 



c. Lateral view of the test, natural size. 



d. The half of a portion of an inter-ambulacral area, and a portion of the ambulacral area, 



with the poriferous zones ; magnified three diameters. 



3 a. Cidaris Botjchardii, Wright, p. 36. Lateral view of a very fine test of this species, 



from the Inferior Oolite. 

 b. One inter-ambulacral plate, and a portion of an ambulacral area of Cidaris Bouchardii, 

 with a small secondary spine found on the test, magnified four times. 



4 a. Cidaris florigemma, Phillips, p. 44. Under surface of a young test, natural size. 



b. Upper surface of the same, natural size. 



c. Lateral view of the same, natural size. 



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



zones, magnified three diameters. 



e. Inter-ambulacral plate and tubercle, seen in profile, and magnified three times. 



5. Diplocidaris Desori, Wright, p. 56. Inter-ambulacral plate, ambulacral area, and 

 poriferous zones ; natural size ; the only fragment I know. 



6 a. Hemicidaris Ramsatii, Wright, p. 83. Lateral view of the test, natural size. 



b. Upper surface, magnified three diameters. 



c. Under surface, magnified three diameters. 



d. Two inter-ambulacral plates, and a portion of an ambulacral area, with the poriferous 



zones ; magnified five times. 



e. The apical disc, magnified once and a half. 



