REPORT ON THE CRINOIDEA. 145 



antarctica are much smaller than those of Antedon eschrichti, even in individuals of 

 equal size, not having more than thirty-five joints, a considerable proportion of which 

 are longer than wide, while the later joints project considerably more on the dorsal side 

 than is the case in Antedon eschrichti (PI. XXIV. fig. 4 ; PI. XXY. fig. 6). This is 

 especially marked in the younger cirri which are of the " small mature " type (PI. XXV. 

 fig. 7), while those which develop in the usual way, though both relatively and 

 absolutely larger, are much more smooth-jointed (PL XXV. figs. 4, 5). 



Eather more of the first radials is visible on the exterior of the calyx in Antedon 

 antarctica than in Antedon eschrichti (PL XXIV. figs. 10, 11; PL XXV figs. 10-12), 

 and in some instances the ends of the basal rays appear between their lower angles 

 (PI. I. fig. 6a). As in Antedon eschrichti the shape of the second radials depends con- 

 siderably upon that of the axillaries. These are always wider than long (PL XXV. 

 figs. 8-11), but vary considerably in shape, even in the same individual. They are 

 almost triangular in some cases, and widely rhombic in others, owing to the strong back- 

 ward projection, which forms a sort of tubercle together with the very convex centre of 

 the second radial. There is a similar variation in the shape of the first pair of brachials 

 (PL XXV. figs. 10-12), and the junctions of the following joints are by no means so 

 tubercular as in the largest variety of Antedon eschrichti, though more so than in the 

 smaller and smoother Atlantic specimens, which have about the same size as the largest 

 individuals of Antedon antarctica that were obtained. In both species alike, however, 

 as in all the members of this group, the fourth to the eighth brachials bear pinnules on 

 their shorter sides. Beyond the third syzygy the arm-joints of Antedon antarctica are 

 even shorter relatively to the width than they are in Antedon eschrichti (PL XXIV. 

 fig. 11 ; PL XXV. fig. 12), and they have a very decided tendency to overlap which is 

 absent in that species, the arms of which are unusually smooth (PL XXIV. figs. 13, 14). 

 The same may be said of the pinnule-joints, especially of the genital pinnules nearest 

 the calyx ; while the long flagellate pinnules on the arm-bases are serrate from end to end 

 in Antedon antarctica (PL XXV. fig. 1-3), whereas in Antedon eschrichti the middle 

 joints are smooth with sharp edges but nothing more. The third pinnule of Antedon 

 antarctica is much more like its successor than is the case in Antedon eschrichti. Its 

 lower joints are considerably stouter than those of the second pinnule, some of them 

 being as long as or longer than wide (PL XXV. figs. 2, 3), whereas in Antedon eschrichti 

 they are distinctly wider than long. In fact the third pinnule of Antedon antarctica 

 resembles the fourth pinnule of Antedon eschrichti rather than its fellow, the third pinnule. 

 In the middle and outer pinnules there is a good deal of variation in the extent of 

 modification in the two basal joints ; but they are never so much flattened and so nearly 

 trapezoidal in form as they are in the larger Antedon eschrichti. 



The centro-dorsal of Antedon antarctica is somewhat more conical than that of 

 Antedon eschrichti (PL I. figs. 6a, 8a), and the axial opening on the ventral surface is 



(ZOOL. CHALL. ESP. PART LX. 18S7.) OoO 19 



