28 Meck and Worthen on Paleozoic Crinoidea. 
soon after, we figured, on page 191, a specimen of Strotocrinus, 
with this body seen in place, and stated that we regarded it as 
having been connected with the digestive apparatus of the 
anima . 
Both in Prof. Hall’s, and our own remarks, this organ was 
spoken of as a convoluted plate. This, however, we now know 
is not strictly correct, for although composed of hard calcare- 
ous matter, and in some species somewhat dense in structure, 
it seems to be always constructed of a great number of minute 
pieces, and generally has a more or less open or porous texture; 
while in some cases it presents the appearance of an exceed- 
ingly delicate net-work. It seems never to be attached to the 
ttom of the visceral cavity, though it extends down nearly 
to the bottom. It is open at both ends (the opening at the 
lower end being generally smaller than the other), and is pla- 
with its longer axis nearly so as to coincide with that of 
the body of the Crinoid. In some species it is more or less 
dilated at the upper end, while in others it is contracted at 
th ends, so as to present, as above stated, the form of the 
shell of a Bulla. It has apparently no columella, but is 
more or less loosely convoluted, with a spiral ridge descending 
-the imterior, and sometimes another ascending the exterior. 
Its walls are generally of moderate thickness, but they often 
appear to be thicker than natural, in consequence of the pres- 
ence of inorganic incrustations, of calcareous or siliceous mat- 
ter, which also disguise its real structure. 
In Actinocrinus Verneuilianus Shumard, this body is nar- 
row below, and subcylindrical above to the top, which is 
slightly dilated. The small opening at the lower end has a 
thickened rim, which passes around spirally, so as to ascend 
the outside, as a rather stout ridge, all the way to the top, 
making nearly two turns, and apparently also forming a rim 
partly around the top. The surface of the whole organ, as 
well as of its external spiral ridge, has the usual rough appear- 
ance, and when fragments of it are held ~~ so as to be exam- 
ined by transmitted light, through a good pocket-glass, it is 
seen to be composed of a great number of very minute polygo- 
nal pieces, varying somewhat in form and size. When these 
pieces are examined under a magnifier, by reflected light, they 
show shining facets, like crystals, though they are evidently 
not surface incrustations, but actually compose the walls, or 
substance of the organ itself. No pores or meshes were obser- 
ved passing through the walls of this organ in this species, 
in which it appears to be more than usually d 
y dense. 
In another specimen in Mr. Wachsmuth’s collection, appar- 
: ently of Actinocrinus proboscidialis, this organ, as seen with 
