A MONOGRAPH OF THE EXISTING CRINOIDS 421 



The pinnule segments have spinous dorsal surfaces, the outermost 4 or 5 bearing 

 long recurved dorsal spines. Terminal combs occur at intervals on the distal 

 pinnules. 



The centrodorsal is rounded pentagonal, discoidal, rising to a height of about 

 0.5 mm. above the dorsal surface of the radial pentagon, and bearing a marginal 

 row of but partially obliterated cirrus sockets. 



The mouth is subcentral. 



The color in alcohol is white, with the disk and perisome light brownish. 



The type of Actinometra rariabilis from Thursday Island was thus described by 

 Bell. 



The centrodorsal is of moderate size, concave in the middle. 



The cirri are X, about 15, marginal in position, about 10 mm. long. There are 

 very faint indications of spines on the most distal segments only. 



The radials are visible. The IBr! are exceedingly wide in proportion to their 

 length and are in lateral contact. The IBr 2 (axillaries) are almost perfectly trian- 

 gular. The IIBr series are normally 4 (3 + 4). The IIIBr series are 2, or 4 (3 + 4). 

 If there is another division, it is 2. 



The 60-90 arms are not very long, and thin. The first 4 or 5 brachials have 

 the sides pretty even and the succeeding are very distinctly wedge-shaped, the distal 

 edge becoming faintly denticulated. Further out the wedge becomes wider and the 

 denticulation disappears. 



Syzygies occur between brachials 3+4, 11 + 12, and 16+17 and distally at 

 intervals of about 4 muscular articulations. 



The pinnules generally are delicate and short, the first rather the longest. 



The disk is as much as 30 mm. in diameter, owing to the extensive development 

 of the interradial plating, which extends to the IIBr axillaries. 



The color is yellowish green, with darker spots, patches, or lines, the ends of 

 the arms and the lower surface darker; or the upper surface may be of a pale flesh color. 



The figure shows a specimen with 64 arms. All of the IIBr series are 4 (3 + 4). 

 All of the following division series are 2 except for 2 IIIBr 4 (3 + 4) series, both 

 internally developed on the same IIBr series and both paired with an external IIIBr 

 2 series. 



In the specimens in the British Museum collected by the Alert at Thursday 

 Island there are 6 postradial axillaries. 



The example from Prince of Wales Channel has 64 arms 75 mm. long. There 

 are usually 6 postradial axillaries. The cirri are VII, 15; they are becoming reduced 

 and show signs of disappearing. 



The specimen from Port Molle is small and immature, with about 50 arms. 

 The centrodorsal has a row of 12 cirrus sockets which in life probably bore functional 

 cirri. One cirrus stump of 2 segments remains. The lateral interradial portion of 

 the disk is completely plated. 



The 2 specimens recorded from Australia (as multifida) by Bell resemble that 

 from Port Molle. Both are small. There are 5 or 6 postradial axillaries. The 

 interradial dorsal perisomic areas are heavily plated. There are no cirri, although 

 the cirrus sockets are well formed. 



