PLATE VI. 



Pseudodiademas from the Lias. 

 Fig. 



1 a. Pseudodiadema Moobeii, Wright, p. 110. Test, the natural size. 



b. Upper surface of the same, magnified two diameters. 



c. Base and mouth opening of the same, magnified two diameters. 



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



ferous zones ; magnified four times. 



Pseudodiademas from the Inferior Oolite. 



2 a. Pseudodiadema depressdm, Agassiz, p. 112. Upper surface of the test, natural size. 



b. Base and mouth opening of the same, natural size. 



c. Lateral view of the same, natural size. 



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



zones ; magnified three diameters. 



e. Fragment of a spine, magnified four diameters. 



f. An entire spine, magnified four diameters. 



g. Base of an ambulacral area, showing the tubercles and trigeminal arrangement of 



the pores in this region, magnified three times. 

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

 i. A small specimen with its spines attached, lying on a block of Pea Grit. 



Pseudodiademas from the Great Oolite. 



3 a. Pseudodiadema pentagon!) m, M'Coy, p. 115. Upper surface of the test, natural size. 



b. Lateral view of the same, natural size. 



c. A portion of an ambulacral area, with the poriferous zones, showing the bigeminal 



arrangement of the pores, magnified four times. 



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



zones ; magnified four times. 

 4. Pseudodiadema Parkinsoni, Desor, p. 114. Test and spines, copied from Parkinson's 

 ' Organic Remains.' 



Pseudodiademas from the Cornbrash. 



5 a. Pseudodiadema homostigma, Agassiz, p. 118. Test, the natural size. 



b. Upper surface of the same, magnified two diameters. 



c. The base and mouth opening, magnified two diameters. 



d. Lateral view of the same, magnified two diameters. 



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



zones; magnified five times. 

 /. An inter-ambulacral plate and tubercle, magnified five times. 



