36 
HOLASCELLA TARAXACUM. 
so numerous that it is exceedingly difficult to count them. So far as I could 
make out 23-27 end-rays arise from the terminal disc of each main-ray. The 
end-rays arising from the central part of the distal face of the terminal main- 
ray discs are nearly straight throughout, and extend in a radius from the centre 
of the spicule. The end-rays become longer, more curved and concave toward 
the continuation of the main-ray axis the farther they are situated from the 
centre of the disc. 
This curvature is restricted to the basal part; the middle- and end-parts are 
always straight. This increase of length and curvature towards the margin 
of the disc is such that the tips of all the end-rays are nearly equidistant and lie 
in the surface of a regular sphere, and that the straight middle- and end-parts 
of all the end-rays lie in radii from the centre of the spicule. In consequence 
of this, and because the crowd of end-rays hides the main-rays, the whole spicule 
appears as a regularly spherical aster composed of numerous straight, concentric, 
and equidistant radial rays. The end-rays are 80-140 n long and 2. 5-3. 5 n 
thick at the base. Towards the middle of their length they are attenuated to 
1.5-2. 5 /d] farther on they again become thicker, and attain a transverse diameter 
of 3.2-5 m at their distal end. At the base and just below the tip the end-rays 
are quite smooth for a short distance. For the remaining greater part of their 
length they are covered with oblique, backwardly directed and backwardly 
curved, conic spines, 1-2.5 ^ long. From the end arises a terminal verticil of 
about fifteen recurved spines. The basal parts of these spines are joined to 
form a disc with strongly convex distal face, from the margin of which their ends 
protrude freely for a distance of 2-3 The terminal spine-verticils (end-discs) 
measure 7.5-12 ^ in transverse diameter. 
The general structure and spiculation of the sponges above described clearly 
show that they are Euplectellidae, whilst the presence of root-spicule bundles 
assign them to the Euplectellinae. Since, however, the upper part is not present 
in any of the specimens, and the state of their preservation is insufficient to deter- 
mine whether the wall of their tubular body is perforated by parietal apertures 
or not, it is somewhat difficult to decide in which genus they should be placed. 
Whether the upper end of the tubular body was open or covered by a sieve-plate 
of course cannot be decided. About the parietal apertures, however, we may 
with some confidence say, for the reasons above given, that the holes now ob- 
served in the body-wall are post mortem artifacts produced by shrinkage and 
maceration and that the sponge possesses no parietal apertures in the fresh state. 
At present three genera, Euplectella, Holascus, and Malacosaccus are dis- 
