REPORT ON THE CRINOIDEA. 155 



Thus then the third pinnule of Anteclon quadrata is only % as long as the second ; 

 whereas in Antedon eschrichti it reaches | of the size of the second, and a similar 

 difference appears in the relative proportions of their component joints. 



There is another consideration which, taken by itself, would have no special probative 

 value ; but it is not without importance when combined with the other evidence 

 given above. Antedon quadrata has been dredged at eleven stations altogether, but at 

 only five of these was it found in association with Antedon eschrichti. The " Triton," 

 "Alert," "Valorous," "Tegetthoff " and "Varna" (bis) obtained examples of this type at 

 localities where Antedon eschrichti did not occur ; and in the last four cases they were 

 only single individuals. 



These facts would seem somewhat improbable if Antedon quadrata is merely 

 an immature stage of Antedon eschrichti as supposed by Levinsen. It is a common 

 experience of Arctic dredging to find individuals of Antedon eschrichti associated together 

 in considerable abundance, and at various stages of development ; and one would 

 therefore not expect to find isolated examples of young individuals, unaccompanied by 

 older ones, quite so frequently as is mentioned above. 



Sladen is the only naturalist, besides myself, who has had the opportunity of directly 

 comparing examples of the two species which were obtained at the same locality ; and in 

 spite of Levinsen's remarks, I am still inclined to think that he was right in separating 

 the two forms. I find it difficult to believe that the fine example of Antedon quadrata 

 which I have figured in the " Varna" report is merely a young stage of the Antedon 

 eschrichti obtained at the same locality ; though I am by no means prepared to state 

 definitely that it is not the case. 



My present impression is that we have to deal with two distinct species, the smaller 

 of which, as I have remarked before, represents a permanently immature form of the 

 larger one. 



Antedon quadrata is another of the species in which the cirri are strikingly dimorphic 

 in their character. The mature cirrus of an Atlantic specimen is shown in PL XXVII. 

 fig. 1, while fig. 2 represents one that is still immature as shown by the relative length 

 of the sixth and following joints. This cirrus has developed upon the ordinary plan, a 

 much earlier stage of which is seen in fig. 4 ; but fig. 3 represents another young cirrus, 

 altogether different in appearance and belonging to the " small mature" type, just as has 

 been described in Antedon antarctica and Antedon australis (PL XXV. fig. 7 ; 

 PL XXVII. fig. 18). In the young individual figured on PL XXVI. fig. 1, the spread 

 of which cannot have been more than four or five centimetres, most of the cirri seem to 

 have developed upon the small mature plan ; but a few rudimentary cirri of the other 

 type are to be found round the margin of the centro-dorsal, and there are more in a con- 

 siderably older though still immature individual. 



The youngest form obtained shows less of the first radials on the exterior of the 



