183 
occur; they have as a rule only two valves, but samples with three 
valves are met with now and then. They are mainly found on.the 
oral side in the non-poriferous areas, especially in the adoral part: 
They vary very considerably in size; the small ones are perhaps 
more rightly to be considered as representing the triphyllous form. 
The tubefeet have a thin, calcarous ring, in one piece, as is the 
case in A. placenta. The spines are exceedinglv diversified, being 
quite different in the poriferous and the non poriferous zones, so 
that there are ten radiating stripes both on the oral and aboral 
sides. On the oral side the spines of the non-poriferous zones are 
considerably longer than those of the poriferous zones, ca. 1,5 
mm against 0,5—0,7 mm; they are almost straight, slightly taper¬ 
ing, closely and finely serrate, excepting the point. Those of the 
poriferous zones (PI. VII. Fig. 30) are characteristicallv bent, slightly 
thickened. The spines of the aboral side are of uniform length, 
excepting a few longer spines in the interradi near the apical 
system. Those of the non-poriferous zones (PI. VII. Fig. 27) are 
extraordinarily thickened at the point, those of the poriferous zones 
like those of the oral side, only somewhat shorter. Of the miliary 
spines those of the aboral non-poriferous zones are rather long, 
straight, with a fairly thick cap of skin at the point (PI. VII. Fig. 
29), the others shorter, curved, with no cap of skin (PI. VII. Fig. 
26). It is a noteworthy faet that those spines, situated along the 
furrows on the oral side, form like a roof cover — especially 
distinet in A. placenta —. Evidently those furrows have a special 
funetion, perhaps serving for conducting food to the mouth by 
means of a ciliary current — or perhaps they have a respiratory 
funetion. — 
In regard to the spines there is quite a conspicuous difference 
between the present species and the Queensland specimens of A. 
placenta ; especially the spines of the non-poriferous zones of the 
oral side are distinetly shorter and those of the aboral side less 
thickened at the point. But I shall not enter upon these details 
at the present occasion. 
I found this species in great numbers in quite shallow water 
on a bottom of a sandy mud in the Inner-Harbour of Napier. A 
specimen of 128 mm length, taken in Wellington Harbour was 
given me by Captain Bol Ion s. This appears to be a record size. 
