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



It has a pinnule on the second brachial, just as in Eudiocrinus varians (PI. VII. 

 figs. 3,4); but the next joint has none, thus affording a parallel to the condition of 

 Antedon informis and Antedon disciformis. On the other hand, one ray does not 

 divide at all till the fourth joint beyond the primary radial, as is often the case in 

 Metacrinus moseleyi and in Metacrinus rotundus, though the axillary is the syzygial 

 joint, and not the second of the series as in those types ; but the second and third bear 

 pinnules just as in Metacrinus. 



The only other bidistichate Antedon, besides Antedon clemens, which has a pinnule 

 on the third brachial and no palmars developed is Antedon marginata (PL XL.). It is 

 altogether a larger species than Antedon clemens, however, with relatively longer and 

 more quadrate brachials, and more numerous cirrus-joints ; while the second pair of 

 pinnules of Antedon clemens are relatively longer than the first and third pairs than is 

 the case in Antedon marginata, and the sides of the rays are smooth, without the lateral 

 processes which are characteristic of that type. 



4. Antedon marginata, n. sp. (PI. XL.). 

 Specific formxda — A. 2. -r-. 



Description of an Individual. — Centro-dorsal saucer-shaped, and bearing some 

 twenty-five cirri on its sides, each of about twenty joints, a few of which are somewhat 

 longer than wide. The terminal joints are rather compressed laterally and have a faint 

 keel, passing into the dorsal spine of the penultimate. 



First radials just visible; the second oblong, and quite free laterally; axillaries 

 pentagonal, about one and a half times their length. The rays are well separated and 

 may divide twice. Two distichals, the axillary without a syzygy. Both radials and 

 distichals are rather convex, rising sharply to the middle of their apposed edges. The 

 outer edges of all the pieces at the sides of the rays, from the second radial to the second 

 brachial inclusive, are marked by irregular projections towards the ventral side. 

 Fourteen arms, of about one hundred and fifty joints, the lower ones thick disks, and 

 their successors more triangular, but wider than long, gradually becoming quadrate 

 and more discoidal again in the middle of the arm. A syzygy in the third, and 

 then between the eighth and thirteenth brachials ; others at intervals of three to six 

 joints. 



The second brachial bears a comparatively slender pinnule of about twenty joints, 

 most of which are longer than wide, and the third has a similar but smaller pinnule. 

 The next pair of pinnules are not much longer than the first one, reaching 10 mm., but 

 they have only ten or twelve very stout and rather elongated joints, which terminate 

 somewhat abruptly. That of the fourth brachial is the larger of the two, and the next 



