C. L, Edwards 
281 
b. Pits. 
Over most of the surface of the body and the aiiibulacral appendnges are found 
shallow, crater-like depressions which may be called pits (Vig. J). 
Fig. J. Pit with thick, pigmented wall. A table lies just beyond the outer edge 
of the pit. X 320. 
The mean dimensions are about "15 mm. x '1 mm. and their centres, in general, 
average about '3 mm. apart. Each has a thickened pigmented wall (Fig. K) in 
which epidermal cells are crowded and which is more or less clearly separated 
from the surrounding tissue by crescentic clefts (x). 
I 
Fig. K. Section of pit; pit; .t, .r, clefts separating wall from surrounding tissues; 
I, lacuna ; s, s, spaces from which tables have been dissolved, x 400. 
The opening of the pit is either approximately circular (Fig. J) or else slightly 
elongated and about -057 mm. x -03 mm. At times when the lip of the pit is 
Biometrika vi 36 
