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



The first radials partially visible ; the second short and oblong. Axillaries 

 triangular, twice the length of the second radials, and forming with them a more or 

 less distinct median tubercle. The first two brachials wedge-shaped (the first least so), 

 with sharp outer edges and a similar median elevation in their line of union. Ten 

 arms of about one hundred and sixty short joints, which are wide and nearly oblong 

 till the second syzygy, after which they are narrower and more triangular, gradually 

 becoming more oblong again and finally square at the ends of the arms. The middle 

 of the distal edge of each joint in the lower part of the arm is slightly raised, and 

 gradually develops into a keel or crest curving slightly forwards. This may follow 

 immediately after the median tubercle between the first and second brachials, or not 

 begin till after the twentieth joint, and varies very much in its development, gradually 

 becoming less marked towards the ends of the arms. Syzygies in the third and about 

 the eighth and twelfth brachials, and then at intervals of two to eight joints, usually 

 about four or six. 



The lower pinnules are all of tolerably equal length. That on the second brachial 

 is about 12 mm. long, rather slender, and consists of some twenty trihedral joints, 

 most of which are longer than wide. The following pinnules have rather wider and 

 more flattened joints, with a sharp dorsal edge, and they gradually increase in stoutness 

 till that on the sixth brachial, which is the largest pinnule on the arm. The next few 

 pinnules decrease slowly in stoutness but increase in length, their outer joints becoming 

 relatively longer, but the basal ones remain wide for some distance ; the terminal 

 pinnules long and filiform. 



Disk and ambulacra naked ; sacculi very abundant on the disk, arms, and 

 pinnules. 



Colour in spirit, — very variable ; light brown, purple, or various combinations of 

 the two, either mottled or in broad or narrow bands ; other specimens are mottled 

 purple and white. 



Disk 11 mm.; spread about 25 cm. 



Locality. — Bahia, 7 to 20 fathoms. 



Other Localities. — Off St. Lucia (278 fathoms); Venezuela; Pernambuco ; the 

 Abrolhos Islands; Rio Janeiro; Chile; Java (?); Ceylon; the Seychelles; Muscat; 

 Aden ; Red Sea ; Zanzibar ; Mauritius ; Madagascar ; St. Helena. 



History. — This species has a wide distribution in the littoral zone of the tropical 

 and the southern subtropical seas ; and it is not improbably therefore identical with 

 the Alecto carinata of Leach, 1 who defined his type very briefly from a specimen sine 

 patriot, in the British Museum. But the originals of Leach's species are not now to be 

 found in the national collection, although Professor F. J. Bell has made a careful search 



1 Zool. Miscellany, 1815, vol. ii. p. 63. 



