A MONOGRAPH OF THE EXISTING CRINOIDS 279 



uular; occasionally these become more nmneroiis, forming a very loose and rudi- 

 mentary narrow crescentic meshwork about the distal border of the marginal lappets. 



The spicules in the tentacles arc unusually abimdant, and often form along the 

 distal side a continuous meshwork reaching nearly to the tip. 



The disk is naked; the mouth and anal tube are about equally excentric. 



A'Otes. — Hartlaub described his Adinometra echmoptera var. carinata especially 

 on the basis of specimens from Grenada. 



The centrodorsal is discoidal, sometimes sharply pentagonal, of varying size, and 

 usually with the dorsal surface slightly convex. The cirrus sockets are arranged in a 

 partially double marginal row. 



The cirri are up to XXV, 14-15, very slender and strongly compressed distally. 

 The third-fifth segments are greatly elongated and are centrally constricted. From 

 the seventh onward the segments are uniformly short and have a weak dorsal keel 

 which distally rises into a small terminal dorsal spine. 



The radials are concealed. The IBr, are short and laterally free. The IBr2 

 (axillaries) are almost or quite triangular, with a slight proximal convexity of the 

 lower border and a somewhat depressed surface. 



The 10 arms are very slender, from 60 to 75 mm. in length. Their surface is not 

 smooth. The brachials are moderately long. The first brachials are short and are 

 closely united interiorly. The second bracliials are somewhat longer and are free 

 interiorly. The first syzygial pair (composed of brachials 3 + 4) is still longer. The 

 fifth and sixth brachials are somewhat shorter again. All of these brachials, like 

 those following, have somewhat everted ends. The seventh and eighth brachials are 

 wedge-shaped, intermediate between the preceding and the following triangular 

 brachials. These triangular moderately long brachials have everted ends, but do not 

 overlap the brachials succeeding. The syzygial pairs are remarkable for their unusual 

 length. Toward the ends of the arms the brachials become elongated and bluntly 

 wedge-shaped. 



Syzygies occur between brachials 3 + 4, again from between brachials 12 + 13 to 

 between brachials 14 + 15 (often between brachials 13 + 14 or 14 + 15), and distally 

 usually at intervals of 3 or 4 musuclar articulations. 



The pinnules are all slender and flagellate. The comb on the proximal pinnules 

 is well developed, and sometimes occurs on P4. On Pi the comb involves 14-16 

 segments. P2 is somewhat shorter and more slender than P,, and P3 is somewhat 

 shorter and more slender than P2. P, is the smallest pinnule. The pinnules succeed- 

 ing P4 gradually increase in length. The proximal pinnules from P, to P3 on the 

 lower half of the distal edge are strongly toothed, as a result of the individual segments 

 being here produced and these productions being beset with small spines. This 

 condition does not occur beyond P3. On Pi and Pj, and to a greater or lesser extent on 

 P3, the 2 basal segments contrast strongly with those following through their superior 

 size and breadth. In most of the specimens these 2 segments are conspicuously 

 keeled. The segments of the distal pinnules are, with the exception of the basal, 

 elongated and somewhat constricted centrally. 



