capitate rays vary, in different spicules, very much in their 
form and dimensions, some are very small, cylindrical and 
blunted, others, at the point of junction with the shaft, are as 
stout as the shaft itself and become gradually pointed, whilst 
in other spicules the head rays are largely developed, fre- 
quently accompained by a diminution of the shaft, which in 
the extreme forms is reduced to a small blunted process. 
Neither are the rays themselves uniform, very often one is 
longer or shorter than the others of the same spicule. Another 
feature of these capitate rays is that one or all of them may 
bifurcate and the divisions, like the simple rays, are often of un- 
equal length. That this bifurcation of the capitate rays is 
only a further development of the growth of each ray and 
not characteristic of a particular form of spicule, is evident 
by the numerous examples in this flint meal, in which a 
gradual transition may be seen from specimens which have 
all the rays simple, to those in which one, two, and finally all 
three of the rays are bifurcated. 
For this form of spicule in which the shaft is very pro- 
minent in relation to the head rays, as well as for those in 
which the shaft has been reduced, but can yet be recognized 
as distinct from the head rays, I propose to employ the term 
«trefid» spicule, and where the rays are simple, to denominate 
the spicule «szmple trifid,» and where bifurcate, «compound 
trofid.» 
The other main form of quadriaxial spicule has the four 
divisions or arms more or less like each other, so that it is 
not easy to determine which of them corresponds to the shaft 
of the trifid spicule. In a very few instances one of the arms 
of these spicules has been extended beyond the central point 
so that a five rayed spicule results. The arms of these four 
rayed spicules sometimes radiate from the centre at an equal 
angle from each other, but in other examples one arm is at 
a more or less open angle and occasionally nearly at a right angle 
to the other three arms. A few of these spicules also have 
