128 BRITISH PALASOZOIC SPONGES. 
11. Dicorvopnyron Dansyi, M‘Coy, sp. Plate II, figs. 4, 4 a, 4b, 4. 
1852. Trerraconts Danpyr, M‘Coy. Brit. Pal. Foss., p. 62, pl. i», figs. 7, 8. 
1854, — _— Morris. Cat. Brit. Foss., p. 90. 
1872. — _ Murchison. Siluria, 4th edit., p. 509. 
1873. _— — Salter. Cat. Cambrian and Sil. Foss. Cambridge, 
p. 176. 
1880. — — F. Roemer. Lethea pal., p. 304. 
1881. — — Whitfield. Bulletin Amer. Mus. Nat. Hist., No. 1, 
p. 14. 
1883. - _— F. Roemer, Geitschr. d. deutsch. geol. Gesellsch., 
p- 707. 
1883. Dicrvornyron Danpyt, Hinde. Cat. Foss. Sponges, p. 131. 
Sponges sub-ovate or sub-conical in form, growing from an obtuse basal point, 
without stem, root, or point of attachment, the base is flattened or convex, the 
greatest width in some specimens is just above the base, in others about half the 
height of the Sponge, from this it gradually tapers to the summit, which appears 
to have been open. The specimens vary between 23 and 30 mm. in height, and 
from 14 to 17 mm. in width. 
The Sponge-wall appears to have been smooth and even; the larger areas of the 
rectangular meshwork are marked out by more prominent, vertical, and transverse 
raised lines, and vary from 1°5 to 3 mm. in length, and these are subdivided by 
finer lines into smaller squares, the sides of which are about °75 mm. inlength. In 
some cases the stronger lines forming the larger squares are nearly parallel from 
the base to the summit, whilst in others they converge to each other towards the 
base. , 
No spicular structure whatever has been preserved in any of the specimens yet 
discovered, which are merely casts in a matrix of micaceous sandstone. No struc- 
ture can be detected in the interior of the specimens. 
Mr. Salter, according to M‘Coy’s statement, referred this species to Receptacu- 
lites; by M‘Coy himself it was placed in the genus Tetragonis, Kichwald, and 
apparently regarded as belonging to the Hchinodermata ; and in Morris’s Catalogue 
it is also placed in this group. Ferd. Roemer likewise includes this species under 
Tetragonis, and calls attention to the resemblance between the surface characters 
of another form of this genus and Dictyophyton. Subsequently I placed the species 
in Dictyophyton, as its structure, so far as a comparison is possible from merely the 
casts of the organism, agrees closely with that of D. tuberoswm, Conrad, the type 
of the genus. It is now known that the genus Tetragonis, Kichwald, is merely a 
synonym of Ischadites, Murch., and its characters markedly differ from those of 
Dictyophyton. 
