140 ARTHUR DENDY. 
which, owing to the state of preservation of the fossils, will 
perhaps never be decided. 
Zittel (3) regarded his Pharetrones as the ancestral forms from 
which the living calcareous sponges (Ascones, Leucones, and 
Sycones of Haeckel) originated. I need hardly say that I do not 
agree with this view, and I have endeavoured to show in this 
paper how a “spiculo-fibrous” skeleton may have been derived 
from the more primitive Syconoid type. My arguments, how- 
ever, obviously apply only to the case of Lelapia, for the 
minute structure of other calcareous sponges with a fibrous 
skeleton is not sufficiently well known to justify speculation as 
to their origin. Thus it is possible that the fibres of those 
Pharetrones which are described by Zittel as consisting of 
bundles of parallel oxeote spicules are really composed of 
elongated, fork-shaped triradiates. Even in Lelapia it is 
hard to distinguish these, in situ, from oxeote spicules, owing 
to the closeness with which they are packed together; and in a 
section of a fossil sponge it would be impossible to do so unless 
one happened to get a section passing just through the fork of 
the spicule and in the plane of all three rays. 
All things considered, then, it seems unadvisable, in the 
present state of our knowledge, to introduce the family Phare- 
trones into our system of recent Calcarea, and Lelapia may 
be regarded simply asa very specialised type of the Grantidz. 
MeExLBourNE, November, 1893. 
REFERENCE List or LITERATURE. 
1. Denpy.—“ Studies on the Comparative Anatomy of Sponges: V. Observa- 
tions on the Structure and Classification of the Calearea Hetero- 
cela,” ‘Quart. Journ. Micr. Sci.,’ vol. xxxv, N.8., p. 159. 
2. Carter.—“ Descriptions of Sponges from the Neighbourhood of Port 
Phillip Heads,” ‘ Annals and Magazine of Natural History,’ vol. xviii, 
ser. 5, p. 126. 
3. ZitTEL,— Studien iiber fossile Spongien, Dritte Abtheilung,” ‘ Abhand- 
lungen der k. bayer. Akademie der W.,’ II Cl., Bd. xiii, Abth. ii, 1878. 
