PLATE XV=. 
1, 2. Clypeaster Ravenellii A. As. 
Fig. 1. Seen from the actinal side, natural size, one half of the test denuded. 
Fig. 2. Part of one of the median ambulacral zones of the actinal side, magnified. 
3, 4. Clypeaster latissimus A. Ag. 
Fig. 3. Seen from the actinal side, natural size. 
Fig. 4. Part of one of the ambulacral zones of the actinal side, magnified. 
