A MONOGRAPH OF THE EXISTING CRINOIDS 371 



as broad as long. Both ossicles are perfectly smooth and evenly rounded dorsally, 

 rising to a low synarthrial tubercle on the line of the articulation between them. 

 Their lateral borders are smooth and straight, never produced, so that the IBr series 

 are remarkable in being very widely separated. The IIBr series are 2, resembling 

 the IBr series though with the component ossicles relatively slightly longer; the 

 IIBr, are interiorly united for their entu-e length. The IIIBr series are 2 and resemble 

 the IIBr series. They are rarely present, and occur only on the outer side of the 

 IIBr series. 



Arms 20 in number (sometimes a few less), from 60 mm. to 85 mm. (usually 

 between 60 mm. and 65 irmi.) in length. The first brachials are wedge-shaped, 

 not quite twice as broad as the interior length, united interiorly. The second brach- 

 ials are of about the same shape and size, with the outer side convex. The first 

 syzygial pair (composed of brachials 3+4) is somewhat longer than broad, more 

 rarely about as long as broad, with the ends parallel and more or less constricted 

 centrally. The fifth brachial resembles the second. The following brachials rapidly 

 become more obliquely wedge-shaped and after the seventh triangular, as long as 

 broad, with the long outer side concave. Distally the brachials become wedge- 

 shaped again; the terminal 6 to 8 segments are very small and short, falling about 

 3 mm. or 4 mm. short of the tips of the terminal pinnules. The brachials are smooth 

 and do not overlap. 



Syzygies occur between brachials 3+4 (exceptionally 4 + 5), again between 

 brachials 11 + 12 to 13 + 14, and distally at intervals of 3, more rarely 4, muscular 

 articulations. 



Pi is about 7 mm. long, very slender, weak and flexible, composed of 30-35 

 segments of which the first is greatly enlarged, rather over twice as broad as long, 

 rounded oblong with the distal edge concave, the second is also enlarged, about half 

 as broad as the first but nearly of the same length, and those following are very small 

 and about as long as broad. P2 is nearly or quite twice as long as Pj, stout, stiff and 

 spinelike, with the first segment enlarged like the corresponding segment of P, though 

 not quite so much so, the second trapezoidal, rather longer than the first, and the third 

 and following elongate. The third segment is about half again as long as broad and 

 the remainder are about twice as long as broad, or even slightly longer distally. The 

 segments in the outer third or half of the pinnule have slightly overlapping spinous 

 distal ends. There are 20 segments in all. While Pi is roimded triangular in cross 

 section, Pj and the following pinnules are strongly and sharply prismatic. Pj re- 

 sembles P2 but is usually shorter, intermediate in length between Pj and P, ; sometimes 

 it is as long as, or even longer and stouter than, Pj. The following pinnules decrease 

 in length very gradually to P7 or Pg, which is about 5 mm. long, then increase again 

 very gradually to 6 mm. or 7 mm. distally. The first 2 segments of P3 are but little 

 expanded, those of P, and the following pinnules being the same as the first 2 segments 

 of the distal pinnules. The genital pinnules are not expanded, nor are their terminal 

 segments especially different from the others. The distal pinnules have the first 

 segment somewhat wedge-shaped, convex proximally and anteriorly and concave 

 distaUy, the second trapezoidal, about as long as the distal width, and the remainder 

 twice as long as broad except for the terminal, which decrease abruptly in width and 

 have_overlapping and spinous ends. 



