PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 267 



The difference in size between the peripheral and apical cirri is never very strongly 

 marked. 



The cirri are delicate and slender, strongly compressed laterally, and weaklv at- 

 tached to the centrodorsal. They are composed of one or two short basal segments, 

 after which the segments rapidly become more elongated, remaining long to the end 

 of the cirrus or decreasing more or less in length distally. 



The distal ends of the cirrus segments are unmodified, or if the outer segments are 

 short their ends may be slightly produced. The longest segments, the fourth or fifth, 

 and those immediately following, are from 3 to 5 (usually 4) times as long as broad, and 

 are somewhat constricted centrally. The segments may remain similarly elongated to 

 the end of the cirrus, with the penultimate segment half as long as those preceding, 

 tapering, and followed by a perfectly straight terminal claw; they may decrease slightly 

 in relative length but remain elongate; they may decrease to less than twice as long as 

 broad by the antepenultimate; or the terminal 6 or 8 may be about as long as broad. 



The dorsal surface of the cirrus segments is always rounded, and there are no dorsal 

 processes nor opposing spines. 



Basal rays are not developed. 



The radials are usually visible at least in the angles of the calyx where their apposed 

 anterolateral angles form low triangles; their distal border is rarely visible beyond the 

 rim of the centrodorsal. 



In the largest species there is a small narrow subradial cleft. 



The IBr, are short, much broader than long. They may narrow rapidly from the 

 proximal to the distal edge, or the sides may be nearly parallel. They are more or less 

 deeply excavated distally by the obtuse angle formed by the proximal border of the. 

 axillary which, because of their shortness, sometimes completely conceals them in the 

 median line. 



The IBr 2 (axillaries) vary from much broader than long to somewhat longer than 

 broad, and from triangular with the proximal border slightly convex to rhombic with a 

 marked proximal process. The lateral angles extend more or less, sometimes very con- 

 siderably, beyond the anterolateral angles of the IBr!. The distal sides vary from 

 slightly to strongly concave, and the distal angle may be more or less produced. 



In one species (Coccometra nigrolineata) the IBr series are just in apposition later- 

 ally, though they are not flattened against each other; but usually the IBr, are considerably 

 narrowed distally. Moderate synarthrial tubercles are usually present. The sides of 

 the elements of the IBr series bear no processes of any kind, the proximal and distal 

 edges are unmodified, and there is never any ornamentation on the dorsal surface. 



The division series and arm bases lie in planes making a relatively large angle with 

 the dorsoventral axis. 



The arms are invariably 10 in number. They vary in length in mature individuals 

 from 40 to 120 mm., and are usually between 50 and 100 mm. The average length for 

 all the species is about 60 mm. 



In structure the arms closely resemble those of the Antedoninae, with the exception 

 of a single species. The first brachials are usually wedge-shaped, longer outwardly 

 than inwardly, with the inner sides in contact or united basally, or sometimes for as 

 much as their proximal half; but they may be so deeply incised by the second brachials 

 that the inner half is almost bandlike and the outer triangular. 



