MORPHOLOGICAL PART. 43 
cirri, although they may be arranged singly at wide intervals, are located 
radially in dicyclic Crinoids, and interradially in monocyclic ones. This is 
readily perceived on pentangular stems, in which the cirri rest within the 
retreating angles of the joints, so as to alternate with the salient angles, and 
hence are in line with the salient angles of the axial canal. 
The length of the cirri among Camerate Crinoids was very variable, and 
they were in some species quite formidable. We have in our collection a 
fragment from the lower part of the stem, apparently of Batoerinus grandis 
(Plate I, Fig. 2), measuring 11 em. in length, and tapering from a diameter 
of 10 mm. at one end to 7 mm. at the other. It gives off numerous cirri, of 
which those of the thicker or upper end are but little thinner than those of 
the lower. Three of the lower cirri are preserved to a length of 16, 151, and 
15 em. respectively, and may have been much longer, as they taper but 
little, still having at their ends a thickness of 21 to 3 mm. Five other cirri 
are broken at a length of from 11 to 37 mm., and eight consist of only two 
to five joints ; while the sockets of three others are empty. The sockets are 
deeply excavated, and extend to nine joints, the surface being radiated. The 
distal faces of the joints are slightly concave, the proximal joints shorter than 
the distal, and the central perforation is round and of moderate size. Two 
of the cirri in this specimen have a remarkable cyst of 14 to 18 mm. in 
length by 9 mm. greatest width, one forming the distal end of the longest 
cirrus, the other commencing about 8 mm. from the stem. The two thickest 
joints in the inflated part of the one are nearly 4 mm. long, while the length 
of the joints above and below the inflation does not exceed 1} mm. Similar 
cysts are frequently found along the stem, but have not before been ob- 
served to occur on the cirri. They resemble the Myzostoma cysts, which 
occur along the arms of recent Comatule, and like them were evidently 
caused by parasites. 
In another stem fragment from the Upper Helderberg of Louisville, Ky., 
every joint is cirrus-bearing, and most of them have five large cirri — some 
four or three — which almost touch those above and below. The cirri are 
preserved to a length of 35 to 40 mm., and were probably much longer 
(Plate I., Fig. 3). 
The cirri of the Actinocrinidx generally extend to one third the height of 
the stem. They vary greatly in size, and are arranged at rather wide inter- 
vals. The same structure probably prevailed in the Ichthyocrinide, at least 
in Onychocrinus and Taxocrinus ; while in the Calyptocrinide cirri occur only 
