Pores in Fistiilate Crinoids. — Springer. 149 
at their sides, or perforated by pores." How general the" rule 
is I am unable to say, as in the majority of fossil forms the 
preservation is insufficient to show the true structure. Upon 
the theory that these pores were subservient to respiration, 
it would be reasonable to expect them to exist generally in 
those Fistulata which were not provided with a madreporite 
as in Cyatliocrimis. But I am as yet unable to prove that 
such is the case. There are certain Poteriocrinidas in the Bur- 
lington limestone, e.g. P. doris, with a very large and often 
well preserved ventral sac, in which I have not been able to iden- 
tify any pores in the parts of the sac which are exposed. There 
are depressions, very similar to those figured by Bather in 
Botryocrimis and , Thenarocrinus, which run to the angles of 
the plates, in the bottom of which the sutures ean be seen to 
meet. These are totally dififerent structures from those il- 
lustrated in this paper, and I cannot assert that any pores ex- 
ist in them. In these forms the sac was of enormous size, and 
we scarcely ever have it preserved to the distal end. It may 
be that the pores existed at some other part than that ob- 
served, but this is only conjecture, without present proof. 
To this extent, therefore, the statement made by Wachsmuth 
and Springer on this point in the Revision of the Palseocrin- 
idse was somewhat more general than the proved facts bear 
out, but as limited in the Monograph it is strictly correct. 
EXPLANATION OF PLATE XVI. 
Parisocrinus snbra)nosus M & G. 
J I 
Fig. I. Specimen showing part of perforated ventral sac — ^ 
Fig. 2. Single plate of same, showing the large, round pores, 
penetrating the plates on the suture lines at the middle 
of the sides, in the depressions between the ridges \ 
Fig. 3. Part of ventral sac of another specimen near the distal 
end, from which all surface ornamentation has been re- 
moved by grinding, exposing the sutures and the pores 
at the sides of the plates .• •,' 
Fig. 4. Transverse section at the upper end of same specimen, 
showing pores passing through the plates to the interior 
of the sac ^' 
