309 
Henricias from there likewise forms two such groups. But while 
Ben ham regards all as belonging to one and the same species, 
I think they represent two distinet species, viz. Henricia lukinsii — 
Benham’s “Set A” — and the form here designated as Henricia 
compacta, \SiV. aucklandiæ — Benham’s “Set B”. It is true that 
some of the younger specimens of H. lukinsii look rather inter- 
mediate, because of their arms being siender as in the present form. 
But the adult specimens are so different in general aspect and in 
some structural details that they can, in my opinion, decidedly not 
be referred to the same species. 
The present form differs from H. lukinsii in the arms being 
mueh longer and slenderer, not swollen at the base. The incisions 
at the base of the arms and the depression in the oral interradial 
areas, so characteristic of lukinsii, are lacking. The spines on the 
adambulacral, intermediate and marginal plates stand in groups, not 
monoserially arranged as in lukinsii. However, these groups may 
form more or less distinet vertical series. The spines of the 
intermediate plates form a distinet group on each plate, while in 
lukinsii these spines are contiguous with the adambulacral spines, 
the intermediate series being therefore distinetly discernible only 
on denuding the arm. In the present form the intermediate series 
of plates is distinet oearly to the end of the arm or at least in the 
proximal two thirds. Both series of marginal plates distinet and 
regular. (Fig. 15.b). 
The differences here pointed out seem to me to leave no doubt 
but that this form is entirely distinet from H. lukinsii. Whether it 
is then to be referred to H. compacta or it represents a third species 
I do not venture to decide, my material of both these forms being 
altogeth'er too insufficient. There is no doubt that the Auckland 
form is nearly related to H. compacta, but it differs rather markedly 
from this species in the spinelets being less robust and fewer in 
each group. Also the madreporite is mueh more distinet in the 
Auckland form than in my specimens of compacta. — In short, 
until a rich and well preserved material of both forms becomes 
available, enabling us to form a definite judgment of the constancy 
of the differences between these two forms, I think it the safest 
course to designate the Auckland Isl. form as a variety of H. 
compacta. 
