A MONOGRAPH OF THE EXISTING CRINOIDS 473 



The specimen from Bassett-Smith Bank is small, with a remarkable development 

 of interradial plating. 



As described by Carpenter, the specimen from Banda which served as the type of 

 Actinometra duplex has the centrodorsal a rounded and slightly convex disk, bearing 

 marginal cirri. 



The cirri are about XV, 14-17. The cirrus segments are tolerably uniform. 



The radials are visible. The IBi'i are partly united laterally. The IBr series 

 are quite free laterally. The IIBr series are 4 (3 + 4). The IIIBr series, when present, 

 are 2 externally, but 4 (3 + 4) internally. All the succeeding division series are 

 4 (3 + 4). IVBr series, and rarely VBr series, are present. 



There are 45 arms 105 mm. long. The anterior arms consist of 120 slightly 

 overlapping triangular brachials which gradually become quadrate. The posterior 

 arms are shorter, with only half as many brachials. 



Syzygies occur between brachials 3 + 4, 13 + 14, and 18 + 19, and distally at 

 intervals of 4 muscular articulations. 



P D is relatively long and stout, reaching 13 mm., and that on the IVBr series, 

 which is but little smaller, is nearly twice the length of PI. The pinnules on the next 

 3 brachials are still smaller, after which the size again increases, though the terminal 

 pinnules are not especially long. The first few pinnules have a well-marked comb 

 which becomes gradually weaker and is lost after the tenth brachial. 



The disk is naked, 15 mm. in diameter. The mouth is interradial. Some of the 

 hinder arms have very faint grooves, and others none at all. 



Carpenter said that the great difference in length between the anterior and 

 posterior arms of this specimen is very striking, the more so as most of the hinder 

 arms have grooves, though only faint ones. The 5 hinder arms of the left anterior 

 ray are, however, altogether devoid of ambulacra, as the groove which should supply 

 them suddenly stops quite short on the disk at the base of the IIBr series. The right 

 or western curve of the horseshoe passes by them altogether on its way to the left 

 posterior ray. 



Carpenter noted that in this specimen IVBr series occur on all the rays but one, 

 and in the anterior half of the ray regeneration has taken place to such an extent that 

 there is a VIBr series. He considered this as probably not the normal condition. 



I examined this specimen in the British Museum and found it to be a quite 

 typical young individual. 



The 2 small specimens from Banda which served as the types of Actinometra 

 regalis were thus described by Carpenter. The centrodorsal is a rudely circular disk 

 much hollowed in the center and bearing marginal cirri. 



The cirri are XV-XX, 15. The cirrus segments are nearly equal, and the penul- 

 timate bears no opposing spine. 



The radials are visible. The IBr, are closely united laterally. The IBr 2 

 (axillaries) are short, widely triangular, and in contact laterally. The rays may 

 divide five times but do not spread much, as the first ossicles beyond each division 

 are closely united laterally. The division series are united by interradial plating to 

 the level of the IIBr axillaries or slightly beyond it. All of the division series beyond 

 the IBr series are 4 (3 + 4). 

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