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



have separated them. The large size of the centro -dorsal and the lateral flattening of 

 the rays appear in both types. But in Antedon similis the greater part of the second 

 radials is concealed (PI. XLVII. fig. 1), which is not the case in Antedon brevicuneata ; 

 while the lower pinnules are smaller in the latter type, though it is individually of 

 larger size and has palmar axillaries developed on all the secondary arms instead of on 

 the outer arms of each ray only. The fourth pinnule of Antedon similis is similar to 

 and of almost the same length as the third ; whereas in Antedon brevicuneata it is a 

 good deal shorter and has a smaller number of joints. It is in the proportions of these 

 pinnules and the characters of the second radials that the chief difference between the 

 two types presents itself. 



One of the arms of this specimen bore a Myzostoma -cyst of a somewhat peculiar 

 type. It was entirely independent of the arm- and pinnule-joints, but consisted of a 

 number of relatively large granules of limestone, irregularly aggregated together on the 

 ventral surface of the arm. 



8. Antedon occulta, n. sp. (PI. XL VIII. figs. 1, 2; PI. XLIX. figs. 3, 4). 



be 

 Specific formula • — A. 2. 2. 2.-^-. 



Centro-dorsal a thick disk, reaching 6 mm. in diameter, and bearing thirty -five to 

 forty-five marginal cirri. These have twenty-five to thirty tolerably uniform joints, 

 the later ones compressed laterally with a slight dorsal keel which passes into a faint 

 spine on the penultimate. 



The first radials are entirely concealed, together with the greater part of the second 

 and also part of the axillaries. The rays may divide four times, and the lower joints 

 of adjacent rays are in close lateral contact and somewhat flattened, but are not specially 

 straight-edged. Each division is of two joints, the axillary without a syzygy and often 

 somewhat unsymmetrical. Thirty-six to forty-eight arms, of about one hundred and 

 seventy smooth joints, the first few quadrate and the following ones shortly triangular, 

 gradually becoming quadrate again, but remaining much wider than long till near the 

 end of the arm. A syzygy in the third brachial and another between the thirteenth 

 and thirtieth ; others at intervals of seven to seventeen joints. 



The lower pinnules of the inner arms are generally rather smaller than those on the 

 outer arms of each distichal group, and more especially than those on the outer arms of 

 the rays. The first one may be 7 to 9 mm. long, with twenty to twenty -five joints, the 

 lowest of which are rather wide. The second pinnule may have thirty joints, the first 

 half of which are very stout, and reaches 10 or 15 mm. The third is sometimes nearly 

 equal to it, but is more usually considerably smaller both in length and in stoutness, 

 while its successor on the seventh brachial is always much smaller than the pinnule on 

 the fifth. 



