A MONOGRAPH OF THE EXISTING CRINOIDS 33 



the division series there are relatively long, straight, pointed, and scattered spines 

 which are especially numerous along the edges. Occasionally (as in two specimens 

 from Montserrat) these are entirely confined to the ambulacral margins of the ossicles. 



There are 30 arms about 100 mm. long which even at the base, and especially farther 

 out, are strongly compressed laterally. The first brachials are somewhat broader than 

 long and are not entirely in contact interiorly. The second brachials are squarish. The 

 first and most of the second brachials bear spines resembling those of the elements of 

 the division series on their proximal and distal edges. The first syzygial pair (composed 

 of brachials 3+4) is as long as the first and second brachials together. The epizygal 

 (fourth brachial) has several stronger spines on its distal border of which one is especially 

 strong. The five following brachials are approximately as long as broad, and those 

 succeeding are trapezoidal, gradually passing to approximately triangular. The bra- 

 chials remain triangular until about the middle of the arm when they again become 

 trapezoidal. The brachials in the proximal third of the arm are rather strongly saddle- 

 shaped. The five or six brachials following the first syzygial pair have on each side 

 of the distal edge a small group of minute spines, and a single spine on the dorsal surface 

 that also stands near the distal edge. These sharp dorsal spines, which are directed 

 obliquely distally and outwardly, have at first a more central position, but they soon 

 move to the longer side of the brachials so that they come to alternate in position on 

 succeeding brachials. The stoutness of the dorsal spines is already considerable on the 

 seventh brachial, and increases rapidly and markedly; at the same time the form be- 

 comes like that of a curved pick, strongly compressed laterally. The base of the spines 

 becomes constantly longer and finally extends for the entire length of the dorsal surface 

 of the brachials. In the outer half of the arms the stoutness of the spines decreases 

 again, corresponding to the decrease in size of the brachials 



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

 34+35 to between brachials 39 + 40, or even farther out between brachials 45+46 

 in a specimen from Montserrat. Then there is usually an interval of 7 muscular articu- 

 lations, and the distal intersyzygial interval is 4-6 muscular articulations A specimen 

 from Blake station 298 (Barbados) has the second syzygy frequently between brachials 

 21 + 22, and in one arm it is between brachials 15+16. 



PI on an outer arm from a IIBr axillary is weak and slender, and of very variable 

 length, sometimes about 12 mm. long with about 20 segments. P 2 is 13 mm. long. P 3 is 

 of about the same length as P2, but more slender. P 4 is scarcely half as long, with 9-10 

 segments. The segments of all these pinnules are rounded and greatly elongated with 

 the exception of the outermost and the basal which, however, arc somewhat longer 

 than broad; they bear small spines on their distal ends. The pinnules remain of the 

 same length up to about P 7 or P 8 , the length of the pinnules following increasing. The 

 segments of the pinnules meanwhile become thicker and relatively shorter and are no 

 longer angular. Already on P 4 the second segment shows a slight broadening and 

 elongation on the side toward the centrodorsal. Both these features increase markedly 

 on the pinnules following and persist far out along the arm. On the later pinnules the 

 first segment is also broadened, and toward the end of the arms only the first is broad- 

 ened. The pinnules of the middle arm region are commonly G mm. long with about 

 13 segments of which the lowest are much broadened while those following are some- 

 what elongated and taper rapidly. The greatest length of the distal pinnules is 8 mm. 



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