18 DR. F. E. BEDDARD ON 
the differences between the two examples is due to the different 
state of retraction of the rostellum in both. It might be said 
that if we retract the rostellum of the type specimen, a collar 
might be formed such as is shown in the second example sur- 
rounding the depressed rostellum in which the hooks appear. 
While this is quite possible theoretically, it may be pointed out 
that the difference in size seems at first sight and without micro- 
scopic investigation too great to allow of such a comparison. This 
Text-figure 8. 
A. Sexual individual. B. Scolex of same with rostellum retracted. 
C. Anterior end of sexual individual described in P. Z. S. 1912, p. 841. 
will readily be seen on an inspection of text-fig. 8, A & B, which 
are drawn of the correct relative size. It may also well be that the 
thin collar-like edge which bears the hooks in the fresh example 
of Urocystidiwm is a permanent structure, and that there is 
nothing to compare with it in the earlier example. But this 
point cannot of course be settled in the absence of other specimens. 
On the whole it would seem impossible that any differences in 
