PLATE XVIII. 



Artheastee Dixoni, Forbes. (Page 91. 



From the Lower Chalk. 

 Fig. 



1. Actinal aspect; natural size. (Coll. Brit. Mus., 47000.) 

 a. Supero-marginal plate ; magnified 3 diameters. 



Comptonia Comptoni, Forbes, sp. (Page 69.) 

 From the Upper Greensand. 



2. Abactinal view ; natural size. (Coll. Northampton Mus.) 



a. Isolated plate of interradial portion of disc; magnified 6 diameters. 



b. Isolated radial ; magnified 6 diameters. 



c. Lateral view of interbrachial arc ; natural size. 



d. Supero-marginal plate ; magnified 3 diameters. 



