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the inner surface of the test. Some of the branches extend to the ne- 
arly parallel supports which stretch from the ambitus toward the axis, 
near the centre of the interradial area (fig. I, 2). At the distal end these 
supports are fused with the plates which form the ambitus. Nevertheless 
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Fig. I. Diagram of the inner surface of the oral plate, showing the arrangement of 
the water-vascular system. 1, Radial canal; 2, Branch from radial canal; 3, Am- 
pullae; 4, Ambitus; 5, Parallel supports of interradial area; 6, Tube feet; 7, Tube 
feet and tubercies for spines. 
Fig. IT. Inner surface of part of a very small specimen, drawn from life. 1, Parallel 
supports; 2, Ambitus; 3, Ampullae; 4, Irregular skeletal support; 5, Outermost 
branch from the radial canal; 6, Radial canal. 
clusters of Ampullae may be seen in the corners on the radial side of 
the supports (fig. I, 5,6 and IT, 1), and I traced the connecting branchlets 
