305 
This species is very characteristic through its short, blunt arms 
and through the adambulacral armature, which consists of a single 
transverse series of fairly robust spines, invested by a rather thick 
coat of skin. The spines on the adjoining plates are likewise arranged 
in single transverse series in direct continuation of the adambulacral 
series, the senal arrangement 
thus continuing from the am- 
bulacral furrow on to the side of 
the arms. Though not always 
quite regular,this series-arrange¬ 
ment is, upon the whole, a very 
conspicuous feature of the pre¬ 
sent species. Another note- 
worthy feature is the existence 
of a very distinet median de¬ 
pression on the oral side in 
each interradial area; the two 
genital openings are situated at 
the outer end of this depress¬ 
ion. One might suggest that 
these depressions have some 
connection with the brooding 
habits of this species (which 
are, however, totally unknown). 
it should be noticed that the : 
Fig. 15. Skeletal plates from side of arm 
of Henricia lukinsii (a) and H. compacta, 
var. aucklandiæ (b). The series of plates 
are from left to right in each figure : ad- 
ambulacrals, intermediate, inferomargin- 
als, superomarginals. The muscles be- 
tween the adambulacrals are drawn only 
in the two lowermost pairs. ®/i. 
In regard to the skeletal structure 
jries of oral intermediate plates is 
fairly regular, reaching somtimes well beyond, sometimes hardly to 
the middle of the arm. The marginal plates form fairly regular and 
distinet series, though sometimes there is some disorder to a vari- 
ous extent, especially in the superomarginal series, in the proximal 
part of the arm, so that they are hardly discernible from the dorsal 
skeleton (Fig. 15.a).^) 
It should still be pointed out that the statement in Farquhar’s 
description of the type specimen that there is a very large compact 
group of spinelets in the centre of the disc, apparently covering 
the dorsocentral plate, does not hold good of my specimens, which 
1) It is by no means always easy to decide what is the intermediate and 
what the marginal series of plates, especially not without denuding the 
arm. 
Vidensk. Medd. fra Dansk naturhist. Foren. Bd. 79. 20 
