A MONOGRAPH OF THE EXISTING CRINOIDS 87 



quite so long. P 3 and the following pinnules are 3.5 mm. long with the first two seg- 

 ments short (the first somewhat broader than the second), and the third, fourth , and fifth 

 somewhat expanded laterally to protect the gonads. The distal pinnules are lacking. 



The specimen collected by Dr. Th. Mortensen between St. Thomas and St. John 

 hi 27-36 meters may be described as follows: 



The centrodorsal is thin-discoidal with a broad flat polar area. The cirrus sockets 

 are arranged in one and a partial second marginal rows ; the distal row is complete and 

 apparently quite regular, the proximal consisting of sockets interpolated between those 

 of the first or distal row. 



The cirri are short and rather stout, about 8 mm. long, composed of 18-20 segments 

 of which the first is very short and those following slowly increase in length so that the 

 eighth and following are about as broad as their ventral length. The first segment has 

 its distal edge produced into a transverse ridge which has a straight or more or less 

 convex crest. The second and following have the distal edge produced into a high 

 transverse ridge with a straight or more or less concave plain, finely scalloped, or serrate 

 crest which is very prominent at either end; this ridge distally gradually moves anteri- 

 orly, becoming median on the sixth or seventh, soon after moving to a position near the 

 proximal end of the segment and appearing in lateral view as a slender, sharp, erect 

 anterior dorsal spine equal to about one-third the lateral diameter of the segment in 

 height. On about the fifth or sixth segment the transverse ridge becomes a broad 

 tridentate ridge with one large median and two smaller lateral teeth. Toward the end 

 of the cirrus the lateral teeth become smaller and finally disappear so that on the last 

 three or four segments before the penultimate there is only the single median tooth. 

 The opposing spine is longer than the spine on the antepenultimate segment and is 

 erect, subterminal, and equal to the distal width of the penultimate segment in height. 

 The terminal claw is about as long as the penultimate segment and is abruptly curved 

 in the center, becoming slender distally. 



The distal edges of the radials are even with the border of the centrodorsal in 

 the midradial line, but extend anteriorly in the interradial areas; their distal ends 

 are slightly separated. The IBr, are from three to three and one-half times as broad 

 as long; the distal edge is straight and the proximal edge is straight or slightly and. 

 evenly convex; adjacent IBr! form an angle of about 60 with each other interradially. 

 The IBr 2 (axillaries) are broadly pentagonal, about as broad as long; their sides 

 are from one-third to one-half as long as those of the IBri and make with them an 

 angle of about 120. 



The 10 arms are 50 mm. long. 



The first syzygy is between brachials 3 + 4, the second from between brachials 

 11 + 12 to between brachials 14+15, and the third from between brachials 15+16 to 

 between brachials 19 + 20. The distal intersyzygial interval is from 2 to 6 (usually 

 3 or 4) muscular articulations. 



P! is stiffened and more or less spinelike, slender, 6 mm. long, composed of 9 

 segments of which the first is short and triangular, twice as broad as long, the second 

 is trapezoidal, twice as long as its proximal width, the third is nearly four tunes as 

 long as broad, and those following are four or more times as long as broad, the ter- 

 minal becoming shorter again. P 2 is more slender than P,, 6 mm. long with 13 seg- 

 ments most of which are greatly elongated. P 3 is 4 mm. long with 9 segments. P 4 



