ASTEROIDEA 157 



Young specimens may have a variable number of short abactinal tubercles, or rarely 

 of veritable spines, in addition to the integumentary spinelets. Such specimens are 

 likely also to have more prominent and numerous marginal spines and more strongly 

 spatulate subambulacral spines. This form is represented especially well by young 

 specimens from Sts. 159, 170, 175. Apparently these tubercles are later absorbed or 

 remain as scattered survivals (e.g. St. 456). But the spatulate character of the subam- 

 bulacral spines (with or without more numerous marginals) is found in the adult 

 stage and is characteristic of the Bouvet Island specimens as well as of others (e.g. 

 St. 190). 



In contrast to these there are young specimens (e.g. Sts. 45, WS 25, WS 62, WS 65) 

 in which there are no abactinal tubercles while the short marginal spines are restricted to 

 the interradial arc, the plates of the distal half of ray being smooth. The subambulacral 

 spines are not broadly spatulate. Between these two extremes there are intergrades, as 

 for instance at St. 159, where the spinous variation is common. 



The matter resolves itself into the fact that (as in many species) there are two extremes 

 in spine development— " muhispinous " and "paucispinous", with intergrading stages. 

 Sladen's type oi glabra represents the paucispinous forma while Koehler's armata is the 

 multispinous. To the latter the Bouvet Island specimens are referable. 



The absence of marginal spines from the distal plates is not a specific character. 

 Neither does the presence of 2 (or even 3) subambulacral spines on distal adambulacral 

 plates constitute a differential character. Even the paucispinous typical adult of glabra 

 regularly carries on the distal plates 2 subambulacral spines, the form of which varies 

 from narrowly to broadly spatulate, round-tipped to truncate. 



The Shag Rocks specimens are definitely like those of South Georgia, the adults of 

 which are devoid of abactinal tubercles and have the very deUcate integumentary 

 spinelets chiefly on the margin of the abactinal area. As might be expected the Ross Sea 

 specimens are typical glabra. 



One naturally wonders why Koehler, who merged antarctica, magellanica and glabra 

 under one specific designation, was not more suspicious of the qualifications of his 

 armata, the general locality of which (Kerguelen) had already yielded antarctica, glabra 

 and spiculata. 



Apropos the uniting of antarctica and glabra, Sladen distinctly states that in a good 

 series of antarctica from the Prince Edward and Crozet Islands " The spiny character 

 is present in all stages of growth". Adults oi glabra with abactinal tubercles occur only 

 as sporadic variations and are in no wise characteristic. It is not obvious that Koehler 

 ever saw a typical specimen of antarctica. The Magellanic form which he hsts from 

 Burdwood Bank (1923, p. 74) certainly is not. All other specimens listed in his various 

 papers are variants of glabra. 



Porania glabra appears to be the pan- Antarctic form restricted to the region south of 

 the Antarctic Convergence and ordinarily to moderate depths. P. antarctica in reality is 

 sub-Antarctic, and reaches its best development well north of the Convergence. 



Colour note, St. 42, South Georgia : two adults ; one is orange while the other has the 



