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



been impossible, as de Loriol 1 remarks, to differentiate the species from the numerous 

 forms of Antedon which occur associated with it. 



Neither arms, pinnules, nor cirri of Eudiocrinus present any characters which can be 

 said to distinguish them from the ordinary Antedon-tj-pe ; and the disc with its central 

 mouth might be readily taken for that of an Antedon, except for the fact that the 

 primary ambulacra do not divide, but proceed straight on to the five arms (PI. VI. fig. 2). 

 The sacculi which are usually so abundant at the sides of the ambulacra in Antedon, are, 

 however, far less constant in Eudiocrinus. Abundant in Eudiocrinus indivisus, and 

 Eudiocrinus atlanticus, they are scanty in Eudiocrinus varians, and altogether absent 

 in the two remaining species, so far as my knowledge of them extends. 



The cirri of Eudiocrinus atlanticus are described by Perrier 2 in the following terms : 

 — "II n'existe egalement entre les longues pieces des cirrhes dorsaux que de tres faibles 

 coussinets charnus, et les cirrhes, dans le plupart des echantillons, se montrent etendus 

 en ligne droite et rassembles dans une attitude qui rappelle celle que certaines araignees 

 donnent frequemment a leurs pattes." 



" UE. atlanticus est, au point de vue de la locomotion, une interessante modification 

 du type Comatule ; il ne peut en effet, se fixer solidement aux corps etrangers, comme 

 le font les autres animaux du meme groupe, et il est probable qu'il repose le plus 

 souvent les bras et les cirrhes etendus sur le limon de l'Oeean, n'ayant a craindre, 

 dans les profondeurs ou il vit, ni les vagues ni les courants ; mais les masses musculaires 

 de ses bras indiquent qu'il doit etre aussi un habile nageur. La plupart des Antedon, 

 et surtout les Actinometra, sont au contraire organises pour s'accrocher solidement 

 aux corps sous-marins et nagent peu." 



It appears to me that Perrier has (as usual) drawn a somewhat hasty conclusion from 

 the majority of his fifteen specimens of Eudiocrinus atlanticus, with their cirri fully 

 extended. A large collection of Comatulaa at any particular locality is sure to contain a 

 number of individuals with the cirri stretched out in a straight line. Antedon phalangium, 

 for example, has cirri very like those of Eudiocrinus, composed of elongated joints with 

 small interarticular bundles (PI. XXVIII. figs. 1-3). Great numbers of this species, 

 with which Perrier is well acquainted, were dredged by the " Porcupine " off the coast of 

 Tunis. The cirri of some are spread out horizontally ; while in others they are turned 

 directly downwards, so as to form a sort of basket below the centro-dorsal, and in yet 

 others the cirri are mostly bent upwards, so as to lie alongside the arms, as in the 

 examples of Antedon gracilis, and Antedon valida, figured on PI. XV. Indeed all the 

 three positions may occur in the same individual. The same variations appear in the 

 long-jointed cirri of Antedon macronema from Sydney Harbour (PI. XXXVIII. fig. 5). 

 I have seen individuals of this type in which some cirri are horizontally extended, while 

 others make two or three coils round the stem of a sea-weed or other support. The same 



1 Mono£. Crin. foss. Suisse, p. 279. 2 Comptes rendus, 1883, t. xcvi. No. 11, p. V26. 



