PLATE XXIII. 



PENTACEROS BOYSII, Forbes, sp. (Page 80.) 



Prom the Upper Chalk. 



FIG. 



1. Supero-marginal plate ; magnified 4 diameters. (Coll. Brit. Mus., 48083.) 



a. Lateral view of extremity of arm from which the above supero-marginal plate 



was drawn ; natural size. 



b. Dorsal view of extremity of same arm ; natural size. 



PENTACEROS BULBIFERUS, Forbes, sp. (Page 77.) 

 From the Upper Chalk. 



2. Abactinal aspect; natural size. (Coll. Brit. Mus., E. 5042.) 

 a. Madreporite; magnified 5 diameters. 



PENTACEROS BISPINOSUS, n. sp. (Page 87.) 

 From the Upper Chalk. 



3. Actinal aspect ; natural size. (Coll. Brit. Mus., 35482.) 



a. Actinal view of extremity of arm ; natural size. 



b. Infero-marginal plate ; magnified 3 diameters. 



c. Ventro-lateral plate ; magnified 4 diameters. 



