REPORT ON THE CRINOIDEA. 153 



relative proportions. The basal joints are stouter as in the following genital pinnules, 

 and their successors are distinctly longer than wide, indications of which appear in the 

 second pinnule (PI. XXVII. figs. 9, 10, 12, 13). There is no sign of this, however, in 

 Antedon eschrichti, the joints of the third pinnule being as wide or wider than long 

 (PI. XXIV. figs. 8, 9). Furthermore there is generally less trace in Antedon quadrata 

 of the modification of the two lowest joints in the outer pinnules, which is usually so 

 marked in Antedon eschrichti (PI. XXIV. fig. 13), though it is extremely well developed 

 in an example brought by the " Varna" from the Kara Sea. 



Levinsen 1 has recently united Antedon quadrata with Antedon eschrichti, on the 

 ground that the characters of this latter species as stated by von Marenzeller, Sladen, and 

 myself, all present themselves in immature examples of Antedo?i eschrichti. The 

 possibility of this being the case had of course naturally occurred to me ; but I decided 

 against it for various reasons. 



Levinsen is not personally acquainted with Antedon quadrata, but only knows it 

 from the descriptions of Sladen and von Marenzeller, and from my own preliminary 

 account of its special marks, characters which, as I am fully aware, do occur in young 

 individuals of Antedon eschrichti, though not, I think, to the same degree that they do in 

 Antedon quadrata. Had Levinsen been able to compare an example of Antedon 

 quadrata with an equal-sized but immature individual of Antedon eschrichti, I believe 

 that he would have found differences between them which he would recognise as of 

 specific value. 



One of the " special marks " which I mentioned as distinctive of Antedon quadrata 

 when the type was rebaptised, was the very definite quadrate shape of the middle and 

 outer arm-joints (PL XXVII. figs. 5-7) as compared with those of Antedon eschrichti 

 (PI. XXIV. figs. 11, 14), which are much shorter than wide, with their sutures less oblique 

 than in Antedon quadrata. The young Antedon eschrichti also has relatively long and 

 quadrate arm -joints with oblique sutures, and Levinsen assigns this as one of his reasons 

 for uniting the two species. I was of course perfectly aware of this fact when I named 

 Antedon quadrata, and described it as a permanently immature form of Antedon 

 eschrichti. 2 Since the publication of Levinsen's memoir, which only reached me after the 

 preceding pages were written, I have gone into the subject again in the only way which 

 can possibly give a satisfactory result, namely, the comparison of the corresponding arm- 

 joints in equal-sized individuals of the two species. 



Figs. 4, A and B, on the next page, represent the portions of the arms between the 

 fiftieth and sixtieth brachials of two individuals of Antedon quadrata from different 

 localities. In both cases the joints are of an obliquely quadrate shape and nearly as long 

 as wide. But in the corresponding part of the arm of a young Antedon eschrichti of 

 equal size the joints are more nearly triangular and considerably wider than long (fig. 4, c), 



1 hoc. cit., p 413. 2 Proc. Boy. Soc. Edin., 1884, vol. xii. pp. 374-376. 



(ZOOL. CHAIX. EXP. — PART LX. — 1S87.) OoO 20 



