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-fay 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 y. long and 2.5-3.5 ^ 

 thick at the base. Towards the middle of their length they are attenuated to 

 1.5-2.5 m; 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 m 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 ix. The terminal spine-verticils (end-discs) 

 measure 7.5-12 ju 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- 



