PLATE X. 



ASTROPECTEN COTTESWOLDI^, JBuck. 



Front the Stonesfield Slate. 



F[G. 



1 a. AsTROPECTEN CoTTESwoLDiiE, Buck., p. 116. Ventral surface, natural size. 

 h. Disc and portion of ray, magnified three times. 



c. Portion of the ventral surface of a ray, magnified six times, showing the marginal 



bones with their lateral spines, and the ambulacral avenue. 



d. Lateral view of a ray, magnified four times, showing the thorn-like spines attached 



to the distal border of the marginal plates. 



AsTROPECTEN Phillipsii, Forbes. 

 From the Forest Marble. 



2 a. AsTROPECTEN Phillipsii, Forbes, p. 122. Ventral surface, natural size. 



b. Portion of a ray, showing the ambulacral bones, avenue, and tentacule pores, 



magnified. 



c. One marginal bone magnified. 



d. Two marginal bones with their border spines, magnified. 

 ('. Spine magnified. 



AsTROPECTEN CoTTESWOLDI^E. 



3 a. AsTROPECTEN CoTTEswoLDi^. Small specimen, showing details of the dorsal 



surface of the rays. 



b. Dorsal surface, showing marginal plates, and the upper portion of the ambulacral bones. 



c. Ditto ditto of another ray. 



d. Ditto ditto of another ray. 



