373 
M. K. A. Zittel on Fossil Calcispongice . 
As may be seen from this rapid description of the skeletal 
characters of the recent Calcispongias, the fossil forms are 
essentially distinguished from the Ascones, Sycones, and 
Leucones by their generally uniaxial spicules being grouped 
in fibre-trains, in which they lie close together, parallel to the 
longitudinal axis of the fibres, like the arrows in a quiver. 
This peculiarity, in combination with certain characters of the 
canal-system and external form, justifies the establishment of 
a distinct family, for which I propose the name of Pharetrones 
(from cf)ap6Tfja , a quiver). 
Pharetkones, Zitt. 
External form .—As in all other orders, the external form 
of the calcareous sponges, from its instability and multifari¬ 
ousness, furnishes no characters of decisive systematic impor¬ 
tance. We find among the Pharetrones nearly all the peculi¬ 
arities of form which occur among the Lithistidae ; here also 
cylinders, clubs, basins,- cups, leaves, nodules, and ramified 
bushes or twigs are the most common forms, fn general, 
however, the Lithistidae attain much more considerable 
dimensions; whilst among the Pharetrones basins of 70-80 
millims. diameter, or cylinders of equal length, are to be 
regarded as unusually large forms. Nevertheless in average 
size the Pharetrones considerably exceed the existing Calci- 
spongias. 
The walls are of considerable thickness, and consist of solid 
anastomosing calcareous fibres. 
The stomachal cavities may generally be very clearly dis¬ 
tinguished from the canal-ostia or pores of the surface. They 
are sometimes tubularly prolonged and reach from the vertex 
to the base, sometimes funnel-shaped, sometimes shallow or 
even scarcely sunk into the skeletal mass. 
All Pharetrones attach themselves firmly to a support. 
Canal-system .—In many Pharetrones, especially in those 
with a well-developed, impressed stomachal cavity, the canal- 
system agrees with that of the Leucones. Crooked branching 
canals, commencing with their fine ramified ends near the 
surface, and uniting towards the interior to form a stem gradu¬ 
ally increasing in thickness, open into the stomachal cavity. 
These canals generally have a radial course, but in the middle 
of the sponge-body, especially when the stomachal cavity is 
shallow, they sometimes take a perpendicular direction, and 
convey the water from below to the cavity. The canal-ostia 
upon the gastral surface are placed irregularly, and in size 
dependent upon the thickness of the canals. 
In forms with undeveloped stomachal cavity fine crooked 
