A MONOGRAPH OF THE EXISTING CRINOIDS 647 



The 16 arms are 110 mm. in length, and consist of about 120 tolerably smooth 

 brachials. The lower brachials are triangular and relatively long, those following 

 soon becoming distinctly quadrate, then more square, and finally elongated. 



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

 intervals of from 3 to 5 muscular articulations. 



P D is about 8 mm. long, and P 2 is but little shorter. But the next pair are con- 

 siderably shorter, and the size decreases to about the seventh brachial and then 

 increases again, the terminal pinnules becoming very slender and reaching 12 mm. 

 in length. Terminal combs occur on the pinnules of the first 9 brachials, and then 

 irregularly as far as the twentieth. 



The mouth is interradial and the disk is naked. All the arms are grooved. 

 The disk is 8 mm. in diameter. 



The color in alcohol is grayish green. 



Carpenter said that this is a very elegant little species, which may be distinguished 

 from parvicirra by the characters of the brachials. The lower brachials lose their 

 triangular shape very soon and become unequally quadrate. The two sides gradually 

 become more equal until the outline is nearly square, and finally the brachials become 

 almost cylindrical, with slightly oblique ends. The relative length of the lower 

 brachials varies in some of the arms. 



Carpenter said that some specimens from the Nicobar Islands in the museums 

 at Copenhagen and Vienna (see p. 638) should perhaps be referred to this species on 

 account of the length of the brachials. 



Of the 2 specimens from the Tonga Islands in the Copenhagen Museum, 1 has 

 34 arms with all the division series 4 (3 + 4) and VI cirri. The other, which bears 

 Liitken's manuscript name Actinometra mutabilis, has 22 arms; of the 10 IIBr series, 

 8 are 2 and 2 are 4 (3 + 4), and the 2 IIIB series are both 4 (3 + 4). There are no 

 cirri. 



Carpenter's record of this species from the Gilbert Islands (1888) was based 

 upon 2 specimens which had been sent to him by the Museum of Comparative Zoology, 

 and which were subsequently studied by Hartlaub. Both now seem to have dis- 

 appeared. 



According to Hartlaub, 1 of these specimens had a somewhat angular centrodorsal 

 with IX short thick cirri. Only 3 of the postradial series remain. There are no IIIBr 

 series. The IIBr series are partly 2 and partly 4 (3 + 4). Judging from the portion 

 of the animal preserved, the number of the arms should have been 20. 



Hartlaub said that this specimen is intermediate between his typus A of parvi- 

 cirra ( = samoana) and his typus B (=parvicirra + timorensis). The triangular bra- 

 chials in the proximal portion of the arm have moderately smooth edges; further 

 out the brachials become more overlapping, but toward the arm tips more even again. 

 The pinnule segments have the borders armed with fine spines. 



Hartlaub said that the other specimen from the Gilbert Islands also is inter- 

 mediate between his typus A and typus B. In contrast to the preceding, it has a 

 large discoidal centrodorsal, and the cirri are XXIII, about 15. There are 36 arms. 

 Of the IIBr series, 7 are 4 (3 + 4) and 3 are 2. The IIIBr series are all 4 (3 + 4). The 

 union of the elements of the IBr series and of the first 2 elements of the IIBr and 



