A MONOGRAPH OF THE EXISTING CRINOIDS 387 



even before the middle the arm appears very slender. The posterior arms are 

 markedly shorter than the anterior, and are composed of shorter brachials which 

 appear more crowded and give these arms a rougher dorsal surface. They usually 

 have at the base an ambulacral groove without tentacles, the'groove being more 

 rarely wholly absent. The total length of an arm in the larger specimens examined 

 by Hartlaub is about 150 mm. 



Syzygies occur between brachials 3 + 4 (more rarely between brachials 4 + 5; 

 Blake station 249), again from between brachials 10+11 to between brachials 12+ 13 

 (more rarely between brachials 13 + 14), and distally at intervals of from 4 to 7, 

 usually 4 or 5, muscular articulations. 



The pinnules on the arm bases have the proximal portion of the outer profile 

 strongly dentate as a result of the basal segments being short and broad, distally 

 increasing in width, the broad distal border overlapping the narrow base of the seg- 

 ment succeeding. This is most conspicuous at the distal angles of the pinnule seg- 

 ments, and the third and fourth segments are distinguished by especially broadened 

 and finely spinous processes which sometimes similate carinate processes. But the 

 segments may also be triangular {Blake station 249), in which case they are in contact 

 only at a single point. In younger individuals (Cape Frio and the violet specimen 

 from Barbados in the Kiel Museum) the dentation of the profiles of the lower pinnules 

 is more or less wholly lacking and the width of the proximal segments is relatively 

 much less. The distal pinnules are uniformly slender, and their segments, with the 

 exception of the 2 first, are elongated. 



Pi is from 10 to 12 mm. in length, and is composed of about 30 short segments; 

 after the first 5 or 6 segments, which are broadened, it becomes abruptly filiform. 

 A ternoinal comb with weak teeth is clearly distinguishable. P2 is similar to P,, but 

 is only about half as long. P3 is still shorter and is somewhat variable in form, in 

 that only the pointed tip may be slender (French Reef). P2 and P3 are more slender 

 than the pinnules following. From P4 onward the length of the pinnules gradually 

 increases again. P4 and the succeeding pinnules are very similar. Toward the 

 twentieth brachial the processes on the pinnule segments disappear as a result of the 

 segments passing over from a triangular to an elongate cylindrical form. On the inner 

 side of the arm Pj is the shortest pinnule, while Pa is markedly shorter than P,. 

 Only the first 2 pinnules on each side of the arm bear combs. 



In the larger specimens the disk has a diameter of 8 mm. It usually bears a few 

 scattered concretions, especially in the anal area. The ambulacral grooves are 

 sometimes thickly bordered with calcareous plates. The mouth is interradial. 



The color in alcohol is typically Ught brownish yellow, often passing mto whitish. 

 Many specimens (French Reef) are darker, with a tinge of violet (French Reef) or 

 pure brown (Charlotte Harbor), or entirely light violet (Barbados), or piu-e white 

 (Dominica and Grenada). A number of specimens from French Reef and one specimen 

 from Montserrat have 2 usually broad dark longitudinal fines on the arms which dis- 

 tally become united into a single line. Many specimens (French Reef) have a broad 

 dark band running dorsally along the arms which one may interpret as arising from 

 the union of 2 longitudinal stripes. 



