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 Murravii, Forbes. Marlstone near Staithes, enlarged two diameters. 



My collection. 



3 «. — Leckenbyi, Wright. Upper surface, natural size. My collection. 

 3 3. — — — Three ring elements from the upper segment, 



magnified. 



4. ■ — — — Under side of the disk, showing the mouth 



and origin of the rays magnified. 



« 



