326 THE VOYAGE OF H.M.S. CHALLENGER. 



laterally ; the rays and their subdivisions are well separated from one another. Three 

 distichals, the axillary a syzygy. Palmar and post-palmar series of two joints, the 

 axillary with a syzygy. Forty to sixty-five arms, of one hundred and twenty to one 

 hundred and fifty joints, the first few nearly oblong ; the following ones overlapping and 

 shortly triangular, with coarsely spinous distal edges. From about the fortieth onwards, 

 the joints become more oblong, as the arms narrow, and their terminal joints are squarer. 

 The anterior arms may be slightly the longer. 



A syzygy in the second brachial ; the next from the fifteenth to thirtieth, usually 

 about the twentieth, with others at intervals of four to eight, usually five or six, joints. 



The pinnules on the second distichals are nearly 30 mm. long, and moderately stout 

 at the base, but soon become more slender. The following pinnules are on the first 

 joints after each axillary, and the length decreases to those of the fifth and sixth 

 brachials which are not specially small. Their successors increase again slowly. The 

 lowest pinnules have a large terminal comb, which may extend out to the fifteenth 

 brachial ; and the edges of the pinnule joints are fringed with spines. 



Mouth radial or nearly so ; disk naked or with a few calcareous nodules. 



Colour in spirit, — blackish-brown. 



Disk 15 mm.; spread 25 cm. 



Locality. — Banda ; two specimens. 



Other Localities. — Moluccas (Quoy and Gaimard). 



Remarks. — This fine species cannot w T ell be confounded with any other Actinometra, 

 the only form which at all approaches it being Actinometra multiradiata, in which, 

 however, there are normally no post-palmars, while the cirri do not have more than 

 twenty-six joints. 



I have only seen three specimens of Actinometra sentosa, one which was brought 

 from the Moluccas to the Paris Museum by Quoy and Gaimard, and the two dredged at 

 Banda by the Challenger. The Paris specimen was referred by Midler 1 to the type of 

 Asterias multiradiata, Linn., his final diagnosis of the species differing but little from 

 his previous description of the Retzian type, except that he gave the number of cirrus- 

 joints as twenty to thirty instead of simply twenty-four ; while he described forty to 

 fifty arms, instead of thirty to forty, the number assigned by Ketzius. The latter 

 change involved the presence of post-palmar axillaries, to which, however, Muller made 

 no reference. 



I was at first inclined to follow Midler's example, and to describe the two Challenger 

 individuals under the name Actinometra multiradiata ; 2 but I have since examined a 

 greater variety of specimens, and have come to the conclusion that the larger number 



1 Abhandl. d. h. Akad. d. Wiss. Berlin, Jahrg. 1847 [1849], p. 261. 

 3 Journ. Linn. Soc. Loud. (Zool.), 1882, vol. xvi. p. 521. 



