Echinoderms.] 



SUBANTARCTIC ISLANDS OF NEW ZEALAND. 



299 



(c/. Koehler loc. cit., p. 629). Further, the proportion of r to R is liable to a con- 

 siderable degree of variation, for I find the following numbers : — 



Set A. 



d = dried ; s = in spirit. 

 Set B. 



d — dried ; s = in spirit. 



It may be noted that the difference in their present condition of preservation 

 does not account for the difference in proportions ; nor does the difference of locality ; 

 but if these specimens be arranged in order of dimension from the largest (R = 42 mm.) 

 to the smallest (R = 9 mm.) it will be evident that, as the animal grows, the arm 

 increases in length at a greater rate than does the disc. 



Koehler gives measurements of his specimens, whence it appears that they 

 present the same variation in proportions as above noted — viz., r : R varies from 

 1 : 3-33 to 1 : 3-4 ; and Ludwig (1905) notes the variation for H. pagenstecheri as 

 being from I : 3-33 to I : 4-91. 



The various differences led me at first to separate them into what I supposed 

 were two species, since the set A have R = 3r (approximately), while in set B 

 R = 4r (approximately). Moreover, in series A the arms are somewhat swollen at 

 the base, and an interradial furrow traverses the disc, so that the general outline is 

 rather different from that of B, in which the arms taper gradually, and there is no 



