62 
was found off N. S. Wales. The importance of this latter faet is, 
however, considerably lessened through Koehler’s identification of a 
specimen from off the Azores as O.hirta. 1 ) There is, however, a pos- 
sibility that it was really the present species, which Koehler had be- 
fore him. It is especially noticeable that the specimen from the 
Azores had only six arms, while the type of O. hirta has seven. Un- 
fortunately the question cannot be settled at present, because the 
specimen has been lost. I sent a copy of my figures to Prof. 
Koehler asking him to compare his specimen therewith. The 
specimen being then sent to him from the Museum in Monaco it 
was lost on the way. The occurrence of O. hirta in the Atlantic 
must then remain problematic, until new material is available, since 
it cannot be denied that there is mueh more reason to suppose 
that the specimen in question really belonged to O. nidarosiensis , 
which will doubtless prove to occur over a great part of the North 
Atlantic, than to O. hirta known otherwise only from off Australia. 
H. L. Clark 2 ) suggests that Koehler’s specimen was only a 
young O. abyssicola. I would not think it possible that Koehler 
could make such a mistake, O. abyssicola being already in its 
quite young stages (I have examined specimens less than 2 mm 
diameter of disk) quite easily recognizable. Clark’s suggestion, 
however, leads to the question of the relation of the present spec¬ 
ies to O. abyssicola. The faet that abyssicola has five arms, 
would seem beforehand to make it certain that these species have 
nothing with one another to do. This is, however, not a char¬ 
acter sufficiently constant for distinguishing the two species thereby 
alone; specimens of O. nidarosiensis with only 5 arms, and, very 
rarely, even with 7 arms occur; on the other hånd, also O. abys¬ 
sicola may exceptionally have 6 or even 7 arms. But the two 
species are otherwise so sharply distinguished that there can, by 
a careful examination, not be the slightest possibility for mistaking 
one species for the other. Especially the dorsal plates afford an 
excellent distinguishing character, triangular, with an acute inner 
point, well separaled, and with a nearly straight outer edge in abys¬ 
sicola, contiguous, with a truncated inner angle and the outer edge 
') Res. d. Campagnes scientif. Monaco. Fase. XXXIV. 1909. p. 171. 
s ) H. L. Clark. Brittle-Stars, new and old. Buil. Mus. Comp. Zool. LXIL 
1918. p. 310. 
