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Meek and Worthen on Paleozoic Crinoidea. 31 
entertained any other opinion in regard to them, than that they 
are the only passages of communication that could have ex- 
isted between the softer parts occupying the ambulacral fur- 
rows of the arms, and the interior of the body, Mr. Billings 
was the first author, so far as we are at this time aware, who 
called especial attention to them in this regard. e regret 
that we have not space to quote a portion, at least, of his re- 
marks on this subject, and would advise the student to read 
attentively the whole of both of his articles alluded to. 
e specimens at Mr. Billings’s command enabled him to 
trace the courses of the ambulacral canals from the arms, 
through the walls of the body at the arm-bases, and to ascer- 
tain the additional fact that, after passing through the walls, 
they seemed to have turned upward ; but beyond this he had 
not the means of tracing them farther. 
single specimen of Actinocrinus proboscidialis, however, 
in Mr. Wachsmuth’s collection, is in a condition (thanks to the 
great skill of that gentlemen and the exceedingly fortunate 
state of preservation, by which its delicate internal parts re- 
main almost entire, and without any surrounding matrix) to 
throw much additional light on this subject. By very dextrous 
manipulation, Mr. Wachsmuth succeeded in removing about 
half of its vault, so as to expose the internal parts, in place, 
and in an excellent state of preservation. The convoluted 
organ already described in other species is in this comparatively 
large, subcylindrical in the middle, apparently tapering at the 
lower end, and a little dilated at the upper extremity. It 
seems to be rather dense, and shows the usual rough appear- 
ance, but as we had no opportunity to examine any detached 
fragments of it by transmitted light, we did not determine 
whether or not it has pores passing through it, though it prob- 
ably has, at least when entirely free from any inorganic incrus- 
tation. Its slightly dilated upper end seems to stand with its _ 
middle almost, but apparently not exactly, under the middle 
of the nearly central proboscis of the vault ; while at the an- 
terior side of its upper margin, and a little out from under the 
proboscis, it shows remains of a kind of thickened collar, which 
we found to be composed of minute calcareous pieces. From 
this there radiate five ambulacra, composed of the same kind 
of minute pieces as the collar itself, each ambulacrum consist- 
ing of two rows of these minute pieces alternately arranged. 
They are each also provided with a distinct furrow along their 
entire length above. As they radiate and descend from their 
connection with the top of the convoluted frame work of the 
digestive sack, they all bifurcate, so as to send a branch to 
each arm-opening, those passing to the posterior rays curving 
