375 
heaps which may be so much as 2—3 mm in diameter, but which 
hardly form any prominence, except where the skin has been strongly 
contracted. They are of very irregular occurrence, sometimes lying 
quite close, sometimes very sparse; as a rule it appears that they 
are confined to the dorsal interradii, but sometimes they are found, 
though much more sparsely, also in the ventral interradii; they 
may form an irregular series in each interradius, but mostly they lie 
quite irregularly. Small patches may be found among the larger 
ones, and in these especially various stages of development of the 
wheels are met with. The wheels lying not nearly so compact as 
in Ch. nigra, the number of wheels in each heap is not so large 
as in that species, in spite of the larger size of the heap. I have 
counted ca. 125 wheels in one of the larger heaps. The structure 
of the wheel is exactly like that of Ch. nigra, so that I may simply 
refer to the figure of the latter; in regard to size they are more 
varying than in Ch. nigra, from 90—200 Also the spicules of 
the tentacles are of the same shape as in that species. No cal- 
careous spicules are found along the radii or in the skin. 
The tentacles are twelwe in number, with 6—8 pairs of digits, 
gradually increasing in length towards the end of the tentacle, the 
distal ones being about twice the length of the proximal ones. An 
oval, reddish spot is found at the base, between each two ten¬ 
tacles; possibly it is a sense organ. The calcareous ring is com- 
posed of twelwe pieces, the two dorso-lateral interradii having each 
two interradial pieces. The radial pieces are perforate (Fig. 55.b). 
