PLATE XVIII. 

 ARTHRASTER DIXONI, Forbes. (Page 91.) 



From the Lmver 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 G diameters. 



b. Isolated radial; magnified 6 diameters. 



c. Lateral view of interbrachial arc ; natural size. 



d. Supero-marginal plate ; magnified 3 diameters. 



