317 
plates afford any reliable specific differences. The main difference 
apparently lies in the number of arms, A. polyplax having as a 
rule 8 arms, A. insignis only 6; but specimens with 7 arms occur 
in both species, and here especially the difficulty of distinguishing 
one species from the other sets in. Also specimens vith 5 arms. 
(b); c. valve of crossed pedicellaria oiA. polyplax, from Ihe inside; d. valve 
of straight pedicellaria of A. polyplax, from the inside. 
evidently such as have never divided, may occur in both species. 
As a rule it may be said that A. polyplax has more siender arms 
than insignis, and also the colour appears to be different, A. insig¬ 
nis being generally red or purpie, A. polyplax dark gray or brownish. 
The pedicellariæ generally are more numerous in polyplax, and 
also in their structure a slight difference is to be noted, the teeth 
of the valves of the crossed pedicellariæ being somewhat less 
numerous, but somewhat longer in polyplax (cf. Figs. 19.a—c). The 
straight pedicellariæ are, in both species, small, generally with the 
valves ending in three points (Fig. 19.d). In larger specimens the 
papulæ are more numerous in insignis than in polyplax. 
A. insignis is the more Southern of the two species, and not 
known to occur outside the New Zealand seas, while A. polyplax 
is widely distributed also along the Australian coasts. It is, how- 
ever, worth noticing that an evidently very close relative of A. 
insignis oceurs in the Magellanic region, viz. Allostichaster inæqualis 
Koehler.^) — It appears that A. insignis grows to a considerably 
1) R. Koehler. Astéries et Ophiures. Further Zool. Res. of the Swedish 
Antarctic Expedition 1901—1903. I. 1923. p. 50 52. 
