417 
of Edinburgh, Session 1870 — 71 . 
by Professor Loven, of Hyponome Sarsii , a recent crinoid lately 
procured from Torres Strait, had led him to the following general 
conclusions. 
In accordance with the views of Dr Schultze, Dr Lutken, and 
Messrs Meek and Worth en, lie regarded the proboscis of the tesse- 
lated crinoids as the anal tube, corresponding in every respect 
with the anal tube in Antedon and Penlacrinus , and he maintained 
the opinion which he formerly published (Edin. New Phil. 
Jour., Jany. 1861), that the valvular “pyramid” of the Cysti- 
deans is also the anus. The true mouth in the tesselated cri¬ 
noids is an internal opening vaulted over by the plates of the peri- 
som, and situated in the axis of the radial system more or less 
in advance of the anal tube, in the position assigned by Mr 
Billings to his “ ambulacral opening.” Five, ten, or more openings 
round the edge of the disc lead into channels continuous with the 
grooves on the ventral surface of the arms, either covered over 
like the mouth by perisomatic plates, the inner surface of which 
they more or less impress, and supported beneath by chains of 
ossicles; or, in rare cases ( Amphoracrinus ), tunnelled in the sub¬ 
stance of the greatly thickened walls of the vault. These internal 
passages, usually reduced in number to five by uniting with one 
another, pass into the internal mouth, into which they doubtless 
lead the current from the ciliated brachial grooves. 
The connection of different species of Platyccras with various 
crinoids, over whose anal openings they fix themselves, moulding 
the edges of their shells to the form of shell of the crinoid, is a 
case of “commensalism,” in which the mollusc takes advantage 
for nutrition and respiration of the current passing through the 
alimentary canal of the echinoderm. Hyponome Sarsii appears, 
from Professor Loven’s description, to be a true crinoid, closely 
allied to Antedon , and does not seem in any way to resemble the 
Cystideans. It has, however, precisely the same arrangement as 
to its internal radial vessels and mouth which we find in the older 
crinoids. It bears the same structural relation to Antedon which 
Extracrinus bears to Pentacrinus. 
Some examples of different tesselated crinoids from the Burling¬ 
ton limestone, most of them procured by Mr Wachsmuth, and 
described by Messrs Meek and Worthen, show a very remarkable 
