PLATE XIX. 
Fig. 1 a. AsTROPECTEN RECTUS, McCoy. Showing the form and structure of the 
marginal ossicles, a rare occurrence in 
this species. Woodwardian Museum, 
Cambridge. Leckenby collection. 
\h. — — — Three marginal plates enlarged, showing the 
socket-like depressions on each alternate 
plate, and the cellular structure in all. 
^ 2. Ophiolepis Mi; RRAVii, i^or^es. Marlstone near Staithes, enlarged two diameters. 
My collection. 
''^^iifSa. — Leckenbyi, Wright. Upper surface, natural size. My collection. 
3 ^. — — — Three ring elements from the upper segment, 
' magnified. 
4. — — — Under side of the disk, showing the mouth 
and origin of the rays magnified. 
