MORPHOLOGICAL PART. 143 
seem to have been obscured by heavy incrustations of silicious matter at 
both sides, and these incrustations may have produced the apparent dupli- 
cation of the walls (Plate V. Figs. 1, 4, 9, and 12). 
Among the many beautiful examples in the Wachsmuth collection at the 
Museum of Comparative Zodlogy, in which the convoluted organ is pre- 
served, there are two unique specimens (Plate V. Fig. 1] and Fig. 10); the 
former showing the delicate porous texture, the other its position beneath 
the ambulacral skeleton. The collection contains also the remarkable speci- 
men of Macrocrinus verneuilianus (Plate V. Fig. 8), in which the upper end 
of the organ is surrounded by a large annular vessel with five radial and five 
interradial openings. In this species the end of the outer fold turns into 
a narrow thickened strip, which ascends spirally toward a place in the 
direction of the anal tube. This structure differs somewhat from that of 
Teleiocrinus and other genera which have a thickened edge along the lower 
margin of the outer fold passing upward (Plate V. Figs. 1, 3, 12). Ina 
specimen in our collection, either of Strotocrinus or Teleiocrinus, we succeeded 
in removing at one side the two outer folds, and exposed the third or inner 
fold (Plate V. Fig. 4), which has the form of a spindle, thicker at the middle 
and tapering to both ends. It seems that the innermost cavity in all cases is 
spindle-shaped, and that the inner end winds spirally upwards like a screw 
with rather sharp, roughened edges, — the so-called “collar” of Meek and 
Worthen. A connection with the ambulacra has not been satisfactorily 
observed in the specimens; neither the upper part of the organ, nor the 
ends of the ambulacral tubes, have been found in perfect preservation. 
The function of the convoluted organ can only be conjectured, as no 
similar structure has been observed in recent Crinoids; but from its position 
it seems probable that it was connected with, or formed a part of, the 
digestive apparatus. If the latter was the case, the thickened outer end, 
leading toward the anus, may represent the hind gut. 
