PLATE III. 

 i 



Hemicidaris from the Inferior Oolite. 

 Fig. 



1 a. Hemicidaris pustulosa, Agassiz, p. 73. Upper surface of the test, natural size. 



b. Lateral view of the same, natural size. 



c. Two inter-ambulacral plates, and a portion of an ambulacra! area, showing the two 



upper pairs of semi-tubercles and poriferous zones ; magnified three diameters. 



d. A primary tubercle seen in profile, magnified two diameters. 



e. Apical disc, magnified two diameters. 



2 a. Hemicidaris granulosa, Wright, p. 71. Upper surface of the test of a small urchin, 



natural size. 



b. Base of a large specimen, showing the mouth opening. 



c. Lateral view of the same test, both the 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, magnified three times. 



Hemicidaris from the Stonesfeld Slate and Great Oolite. 



3 a. Hemicidaris Stokesii, Wright, p. 75. Test natural size, imbedded in Stonesfield 



Slate. 



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



zones ; magnified three diameters. 



c. Apical disc, magnified two diameters. 



4 a. Hemicidaris Icaunensis, Cotteau, p. 90. Lateral view of the test, an interior 



mould. 

 b. Upper surface of the same, both the natural size. 



5 a. Hemicidaris minor, Agassis, p. 80. Test natural size, showing a lateral view. 



b. Upper surface, magnified two diameters. 



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



zones ; magnified three diameters. 



d. Inter-ambulacral plate and tubercle, seen in profile, and magnified three diameters. 



6 a. Hemicidaris Luciensis, d' Orb., p. 78. Test natural size, showing the upper surface. 



b. Base of the same, showing the mouth opening, both the natural size. 



c. Lateral view of the same test. 



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



zones ; magnified four diameters. 



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

 /. Apical disc, magnified three diameters. 



