PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 783 



45 mm. in large specimens) in length. The 17 cirri present give the following number 

 of segments: 19 (1), 20 (3), 21 (3), 22 (2), 23 (1), 24 (5), and 25 (2). The first cirrus 

 segment is about 3 times as broad as long, the second is usually about twice as broad as 

 long, the third varies from as long as broad to twice as long as broad, and the fourth 

 is usually about 4 times as long as the expanded ends; the following segments are greatly 

 elongated. Toward the end of the cirri, the segments gradually become shorter, and 

 in the best-developed cirri they are scarcely more than 3 times as long as broad ; but in 

 the terminal 8 to 10 segments the cirri taper with increasing rapidity and, correlatively, 

 the segments rapidly increase in proportionate length. The terminal claw is repre- 

 sented by a minute conical button on the distal end of the excessively elongated penul- 

 timate segment. The cirri are few in number, but well developed, large, very long and 

 rather slender, composed of greatly elongated segments; distally they taper, rather 

 abruptly, to a sharp point. The earlier segments have a slight central constriction, 

 the concavity being more marked on the ventral than on the dorsal profile. There is 

 a slight lateral compression in the proximal portion of the cirri which gradually increases 

 and becomes very marked distally. As a whole the cirri of this species exactly resemble 

 those of such species of Pentametrocrinus as have these organs greatly elongated, for 

 instance P. varians and P. semperi. 



The 10 radials usually project conspicuously beyond the rim of the centrodorsal. 

 In the best-developed individuals all of the radials are of approximately the same 

 length, but in most of them 5 of the radials are shorter than the other 5, with which 

 they alternate. In some of the best-developed specimens the radials, or at least the 

 shortest of them, project but very slightly beyond the edge of the centrodorsal; in others, 

 not so well developed, the radials may be as long as their proximal width. 



The 10 arms are slender, and probably between 90 and 100 mm. in length. The 

 first brachials are more or less trapezoidal, from 2 to 3 times as broad basally as long. 

 The second brachials are irregularly quadrate, always somewhat larger than the first, 

 sometimes, though rarely, twice as large. The third brachials are approximately 

 oblong, about as large as the second. The first syzygial pair (composed of brachials 

 4 + 5) is somewhat hour-glass-shaped, about as long in the median line as broad 

 basally, or slightly longer. The succeeding brachials are oblong or slightly wedge- 

 shaped, approximately twice as broad as long. The brachials following the second 

 syzygial pair, which is composed of brachials 9 + 10, are very obliquely wedge-shaped, 

 longer than broad, distally becoming much elongated, four or more times as long as 

 broad, with swollen articulations. The pinnule sockets are situated in the middle of 

 the sides of the brachials except on the epizygals of syzygial pairs, on which they are 

 in the proximal portion. The dorsal profile of each brachial is straight or slightly 

 concave, and there is no production or overlapping of the distal ends. The arms 

 increase very slightly in diameter from the base outward, this broadening reaching a 

 maximum on the first syzygial pair and on the segments immediately following, from 

 that point tapering almost imperceptibly to the tip. 



Syzygies occur between brachials 4+5, 9 + 10, and distally at intervals of from 

 1 to 23 (most commonly 4 or 5) muscular articulations. 



P! (on the second brachial) is from 5 to 7 mm. in length and is composed of 21 to 

 25 segments. In fully developed individuals all the segments are very short and are 

 broader than long; in dorsal profile both ends of the segments are prominent so that in 

 the pinnule as a whole this profile consists of a series of small and rather deep scallops. 



