12 
da 
brium is rather long and slender (as in the M. ta. d. bif.) but 
in a few cases it is shorter than the teeth. I have figured this 
aberrant form in fig. 5 on Plate II. 
7°. st. "The well-known stellates are dispersed throughout the whole 
body; at some places they are extremely abundant. Most of 
them are very small, but with stout radii (fig. 12a, b, e.). In 
the figures 16* and 17 I have represented two of a larger kind, 
forming a transition to the gigantic stars represented in the fi- 
gures 15, 16, 14 and 14* (to see the explanation of the plate). 
Perhaps there is a generic relation between these and the tetraxile 
spicules. 
8°. st?. („elongo-stellate”). They have nearly the same size as the 
small stellate ones. The radii are placed in two or more circles 
around an axis, as the figures 13, 18, 19 and 20 show. 
In examining the surface of the Sponge with a low magnifying 
power, there is in several cases to be seen, on the top, a ramifying 
system of canals and cavities (Pl. I, fig. 8) and in the centrum one 
osculum. The membrane that covers the upper surface is provided 
with many small openings, that we may call the pores. In those speci- 
mens where the penthouse is opened (figg. 1, 5, 7) the broad split 
is covered with a thin membrane provided with numerous such 
pores. (Pl. IV, figg. 114 and 115). Sections show that under this 
membrane there are great subdermal cavities, from which probably 
the incurrent-canals take their origin. 
As regards the ramification of the canals ete. I hope to be able 
of finding it out on my further researches. Among the Sponges of 
the third and fourth expedition I have found a great quantity of 
Thenea muricata; so it may be that, when a good many sections 
are made at least the anatomy of the canal system will become 
clear to me. For the moment I think it is better to say nothing 
more, than is to be seen on a few specimens and only with a 
low power. 
For the moment I distinguish three varieties. 
1. Thenea muricata var. « having a rather smooth surface, a 
light greyish colour, straight roots, often a bundle of long spieules 
