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



and they already show very distinct indications of the peculiarities which are charac- 

 teristic of the type. 



Ludwig * has made some observations as to the comparative distribution of calcareous 

 plates and granules in the Neapolitan examples of Antedon pkdlangium and Antedon 

 rosacea. He finds that while calcareous deposits are more or less developed on the disk 

 of Antedon rosacea, that of Antedon pkdlangium is almost or entirely naked, which I 

 find to be the case also both in Tunis and in Marseilles specimens, and in the Atlantic 

 ones as well. But in the British variety of Antedon rosacea the perisome of the disk may 

 be either naked or bear scattered tubercles containing groups of radiating calcareous 

 spicules, and the perisomatic skeleton of the larval arms and pinnules disappears in 

 later life. I have found no trace of it in any specimens of Antedon rosacea, even in 

 those from the north of Scotland ; though examples of Antedon phalangium from this 

 neighbourhood have delicate plates on the pinnule-ambulacra. Like Ludwig, however, 

 I have found small rods in the marginal leaflets on the pinnules of Antedon rosacea from 

 Naples, and also in a Marseilles specimen ; while in the Tunis variety of Antedon 

 phalangium I find delicate perforated plates, the rudiments of the covering plates 

 which are so largely developed in many tropical Comatulse. They are less distinct in 

 the specimens dredged by the " Dacia," and in those from Marseilles they are reduced 

 to small Y-shaped rods, but little better developed than those of Antedon rosacea. In 

 some individuals of the Scotch variety the pinnule-ambulacra are in this condition, while 

 in others they have delicate, but still very definite plates, as in the examples from the 

 Tunis coast. In those from 220 fathoms off Cape Mondego, however, these plates reach 

 a considerable relative size and have a closer network of limestone rods. There are 

 about three to each pinnule -joint, and they alternate pretty regularly with the sacculi, 

 just as the side plates do in Antedon acoela and in other forms from the Eastern seas. 

 They are much better defined than the side plates of many tropical species, but they do 

 not support any covering plates above them. On the other hand, they are altogether 

 different from the large and oval covering plates of Rhizocrinus, Bathycrinus, and 

 Hyocrinus, which are unsupported by side plates, and rest directly on the pinnule-joints. 

 Their occurrence in Antedon phalangium in the East Atlantic is the more interesting, as 

 the locality is within a few miles of that which yielded Pentacrinus wyville-thomsoni 

 and Antedon lusitanica, both with plated ambulacra; while the latter is the only 

 European Antedon with both side plates and covering plates on the pinnules. 



On the whole I am disposed to confirm Ludwig's observations respecting the greater 

 length of the anal tube in Antedon phalangium than in Antedon rosacea; but the 

 difference is not great, and is of no value as a specific character. The only two 

 species which have any great amount of resemblance to Antedon phalangium are 

 Antedon hystrix and Antedon prolixa. But it differs from both of them in the greater 



1 IJber enige seltenere Echinodernien des Mittelmeeres, Mitth. d. zool. Stat. Neapel, 1880, Bd. ii. p. 54. 



