DR. G. J. HINDE ON RECEPTACULITIDA. S17 
generally parallel with each other, and fresh ridges are intercalated 
as the width of the specimen increases; the transverse ridges are 
generally less regular than the vertical, and are frequently curved 
and discontinuous. On closer inspection these ridges are seen to 
be composed of horizontal spicular rays, and the hexagonal plates 
above form the summits of the spicules (Pl. XX XVII. fig. 1c). The 
horizontal rays are thickest at their central junction with the 
summit-plates, and they gradually taper to their extremities, where 
they are bluntly pointed. They are not altogether equal in length, 
and they usually overlap at their ends. The lateral rays are also 
not unfrequently curved and thus give an irregular appearance to 
the transverse ridges. Central axial canals are clearly seen in the 
rays exposed in a polished transverse section of the type specimen. 
In the character of the horizontal rays, and in their disposition with 
respect to each other and to the head plates, there is the closest 
agreement with Ischadites. It is doubtful, however, whether the 
spicules of Spherospongia were furnished with vertical rays like 
those of Ischadites. No clear evidence on this point is afforded by 
the specimens which I have examined, and their present mineral 
condition is unfavourable for the preservation of minute details. 
Fhe only evidence of the existence of a vertical fifth spicular ray is 
shown by a small knob-like point, projecting towards the interior 
cavity from the central junction of the four horizontal rays, and 
this may represent either an aborted ray or the fractured stump of 
a vertical shaft. There are, as may be supposed from the absence 
of the vertical rays, no traces of an inner layer, and scarcely a 
doubt can be entertained that, in this genus, as in Jschadttes, no 
inner layer existed. 
This genus is characterized by its form and by the regular 
hexagonal figure of the spicular plates, as well as by the presence 
of a small central knob in each, and also by the absence of vertical 
spicular rays. 
The first reference to this genus is by Mr. W. J. Broderip in a 
note to a paper by De la Beche on the Geology of Tor and Babba- 
combe Bays, Devonshire *. Very good figures are given of the type 
specimen—which, however, only shows the character of the outer 
surface—and from these Broderip thinks that it may have belonged 
to the Tunicata. He did not, however, propose for it any generic 
or specific name. Some years later J. Phillips copied the figures 
given in De la Beche’s paper, and stated his belief that the fossil 
was a Cystidean allied to the genus Echinospherites, Wahl. (Sphe- 
ronites, Hisinger), and he named it Sphwronites tessellatus. In 1855 
an imperfect example of the same species was figured in the ‘ Geology 
of Russia’ + under the name of Echinospherites tessellatus. In the 
same year, also, the late Dr. Bowerbank { instituted a somewhat 
fanciful comparison between S. tessellatus, Phill., and the small 
calcareous sponge Dunstervillia elegans ; and T. Austin §, referring to 
* Trans. Geol. Soc. (1882), ser. 2, vol. iii. pl. xx. f. 1, 2. 
t By Murchison, Verneuil, and Keyserling, p. 381, t. 27, f. 7. 
{ Ann. & Mag. Nat. Hist. 1845, vol. xv. p. 299. § Id. p. 406. 
