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



so peculiar that it seems inexplicable why, if Pallas had this form before him, he failed 

 to give a better definition of it. The mode of branching agrees with Milne-Edwards' 

 generic characters, and the whole corallum is fused into a dense mass, 28 cm. high, 

 36 cm. wide, and 10 cm. thick. The stem is relatively slender, and gives rise, close to 

 the base, to a large number of branches in all directions. All the main branches, after 

 a certain course, grow up subvertically. They vary in thickness, and present dilations 

 here and there without regularity. Each branch is beset with a number of short spirally 

 arranged pinnules, which are curved slightly upwards, but have an insertion almost at 

 right angles to the branch. There may be from three to five in one revolution of the 

 axis, and about six or eight to a centimetre. These pinnules vary very much in length, 

 many are slender, only slightly tapering, and from 1 to 1*5 cm. long; others which are 

 longer bear secondary pinnules. These may be 5 cm. long, arched upwards, so that the 

 apex takes a subvertical direction, and then bear secondary pinnules spirally arranged, and 

 varying from 0*5 to 1*5 cm. or more in length ; most are simple, but a few become again 

 divided. The whole corallum is fused into a firm mass, not so much by a confluence of 

 parts as by frequent adhesions between the pinnules of adjoining branches and branchlets. 

 At almost every point of contact a fusion takes place. The spines are elongate, and 

 somewhat related in form to those of some species of Aphanipathes (e.g., Aphanipathes 

 barbadensis). A spiral arrangement is not well marked, but the spines are arranged in 

 longitudinal rows, of which five may be seen from one aspect. The spines are about 

 equal in length to the diameter of the axis in their neighbourhood, and are laterally 

 compressed, ending in a blunt point formed by the lower margin taking a sharp curve 

 upwards to join the upper margin. The members of a row are usually separated by an 

 interval greater than the length of a spine (PI. XL fig. 22). There are a number of 

 specimens in the Zoological Museum at Copenhagen which appear to belong to this species, 

 but differ from M.-Edwards' type, in having a more slender corallum, the branchlets of 

 which are irregularly placed, not in a distinct spiral. The largest specimen is 41 cm. long, 

 30 cm. broad, and 13 cm. thick. The stem near the base has a diameter of 3 mm. The 

 whole outer, and particularly the upper, portion of the corallum is very slender ; there 

 is scarcely any difference between the thickness of the branches and branchlets. The 

 spines are distinctly visible to the naked eye. 

 Habitat. — Indian Ocean (Pallas, &c). 



Arachnopathes clathrata (Pall.), M.-Edw. 



Antipafhcs clathrata, Pallas, Elench. Zooph., p. 212. 

 Arachnopathes clathrata, Milne-Edwards, Coralliaires, t. i. p. 320. 



" A. ramosissima intricate, ramulis confusis ubicpie coalescentibus, junioribus setaceis. 

 Fruticulus modo peclali major, rariusculus ; modo vix semipedalis densiusque ramosus ; 



