A MONOGRAPH OF THE EXISTING CRINOIDS 159 



the longest, reaching 2.5 mm. in length. From this point the length of the segments 

 rapidly decreases to about the twentieth, which is followed by a series of short segments 

 which gradually decrease in size. In correlation with the decrease in size, the dorsal 

 profile of the cirri becomes conspicuously serrate. Many cirri have on the last thirty 

 segments a prominent spine. The opposing spine is feebly developed. 



The radials are just visible. The IBri are short, laterally entirely free, and are 

 not incised by the axillaries with which they form slight tubercles. The IBr a (axillaries) 

 are rhombic, distally strongly broadened, sometimes in close contact with their neigh- 

 bors against which they are sharply flattened laterally. The elements of the IBr 

 series are beset with short blunt spines (in the figure shown chiefly along the edges). 

 Sometimes IIBr 2 series are present. 



The 10-12 rounded and slender arms, which have a very uneven dorsal surface, 

 are about 175 mm. long. The brachials as far as the second syzygy bear on the prox- 

 imal and distal ends small blunt spines that stand out vertically from the dorsal surface, 

 like the elements of the IBr series. The first brachials are moderately short, broadened 

 in the proximal half and with sharply flattened outer sides which are appressed against 

 those of the first brachials of the adjacent postradial series. These laterally flattened 

 sides continue the lateral extensions of the axillaries and with them form an even surface. 

 The first brachials are interiorly united in the proximal half. The second brachials 

 are somewhat longer than the first and are distally broadened. Like the first syzygial 

 pair they are in close contact with the corresponding ossicles of neighboring arms; 

 since it is toward the ventral side this contact is difficult to see. The second brachials 

 are separated from the first by a conspicuous synarthry. The seven brachials following 

 the first syzygial pair are somewhat broader than long, and are centrally constricted. 

 From about the ninth onward the length increases and the shape becomes more tri- 

 angular, remaining so until between about the twentieth and thirtieth. From about 

 the twenty-third brachial (length 2.5 mm.) onward the length again slowly increases. 

 The triangular brachials are followed by others more trapezoidal in shape, and in the 

 outer half of the arms the brachials become strongly overlapping. Their distal ends 

 are strongly produced, and in the outer half of the arms finely spinous. From the 

 distal ends longitudinal grooves run inward over the distal half of the brachials. The 

 arms, which are composed of about 130 brachials, gradually decrease in thickness from 

 the base outward. 



Syzygies occur between brachials 3 + 4, again from between brachials 14 + 15 to 

 between brachials 16 + 17, and distally at intervals of 3 or 4 muscular articulations. 



PI is moderately stiff, 9-11 mm. long with 16-18 short smooth segments of which 

 the first four especially the first two are broader than long. The pinnule is broad 

 and laterally flattened at the base, after about the sixth segment tapering rapidly to a 

 delicate tip. The segments in the proximal half are smooth, with the pinnule edge on 

 the side toward the ambulacrum serrate ; the distal segments have finely spinous distal 

 borders; the second-fifth segments are carinate. The articulation between the earlier 

 segments is less close than that between the outer segments, a feature more pronounced 

 in the pinnules following, the basal segments of which have a somewhat different shape. 

 These are also somewhat flattened, but this flattening comes to an end on the lower 

 segments of P 3 , which is rounded. P a is about 2 mm. shorter than PI and is corre- 

 spondingly weaker. 



