PLATE XXII. 



Pentagonastek obtusus, Forbes, sp. (Page 74.) 



From the Uijper Chalk. 



Fig. 



1. Abactinal aspect ; natural size. (Coll. Brit. Mus., 40400.) 

 n. Madreporite ; magnified 10 diameters. 



h. Lateral view of margin, abactinal side upwards ; natural size. 



2. Actinal aspect of two specimens; natural size. (Coll. Brit. Mus., 35481.) 

 a. Lateral view of extremity of arm of the underlying specimen ; natural size. 



3 a. Dorsal view of extremity of arm ; natural size. (Coll. Brit. Mus., E. 5039.) 

 h. End view of extremity of arm ; natural size. (Coll. Brit. Mus., E. 5038.) 



c. Side view of extremity of same arm ; natural size. 



d. Ventral end of extremity of same arm ; natural size. 



e. Supero-marginal plate ; magnified 3 diameters. 

 /. Infero-marginal plate ; magnified 3 diameters. 

 g. Adambulacral plate ; magnified 5 diameters. 



Pentaceeos Boysii, Forbes, sp. (Page 80.) 

 From the Upper Ghallc. 



4. Abactinal view ; natural size. (Coll. Brit. Mus., 46600.) 



a. Isolated ossicle of disc : mao-nified 4 diameters. 



b. Isolated ossicle of disc ; magnified 4 diameters. 



c. Lateral view of arm ; natural size. 



