PLATE XII. 



Hemipedinas from the Great Oolite, Coral Rag, and Kimmeridge Clay. 



Fig. 



1 a. Hemipedina Corallina, Wright, p. 163. Portion of the base and jaws in situ. 



b. Fragment, with plates and spines, from the Coral Rag, Wilts. 



c. One inter-ambulacral plate, magnified three times. 



d. A primary spine, from fragment b, magnified three times. 



2 a. Hemipedina Morrisii, Wright, p. 166. A fragment of the test, natural size. 



b. Ambulacral area, poriferous zones, and inter-ambulacral plates, magnified four 



times. 



c. A primary spine, magnified four times. 



3 a. Hemipedina Cunningtoni, JFright, p. 167. A fragment of the test, natural size. 

 b. The same, magnified four times. 



4 a. Hemipedina microgramma, Wright, p. 159. Upper surface of the test, natural size. 



b. A lateral view of the test, natural size. 



c. One inter-ambulacral plate, a portion of the ambulacra, and poriferous zones, magnified 



four diameters. 

 4.* Cidaris spinosa, Agassiz, p. 53. Spine, natural size. 



5 a. Cidaris Boloniensis, Wright, p. 53. A flattened spine with prickly ridges. 

 b. A spine with thorny prickles, resembling C. spinosa. 



6 a. Hemipedina Davidsoni, Wright, p. 156. A lateral view of the test, natural size. 



b. The upper surface of the test, natural size. 



c. The under surface of the test, natural size. 



d. One inter-ambulacral plate, a portion of the ambulacra, and poriferous zones; 



magnified six diameters. 



7 a. Hemipedina Woodwardi, Wright, p. 158. A lateral view of the test, magnified 



twice. 



b. Upper surface of the test, magnified twice. 



c. Under surface of the test, magnified twice. 



d. One inter-ambulacral plate, ambulacra, and poriferous zones, magnified six times. 



8. Pseudodiadema mammillanum, Boemer, p. 132. Primary spine, magnified threa 



times. 



9. Pseudodiadema versipora, Phillips, p. 124. Primary spine, magnified three times. 



10. Rabdocidaris maxima, Miinster, p. 65. Primary spine, natural size. 



