HOLCOSPONGIA LIASICA. 231 
the specimens the grooves do not radiate from the summit, but from the middle of 
the front surface. The skeletal fibres are of an open character; they consist 
mainly of the relatively large axial spicules. The dermal layer has a smooth 
surface, resembling in appearance the epitheca of corals, but it can be seen to be 
made up of innumerable three- or perhaps four-rayed spicules of different sizes, 
irregularly intermingled together, so that the rays overlap each other in all 
directions. 
This species is very abundant in the beds at Shipton Gorge. It is related to 
H. sulcata, but differs in form and size, and in the disposition of the surface 
furrows. 
Distribution.—Inferior Oolite. Parkinsoni-zone at Shipton Gorge, Dorset. 
(Collected by Mr. E. A. Walford.) 
39. Hotcosponeia Liasica, Quenstedt, sp. Plate XVII, figs. 5—5c. 
1878. SponGiTEs Liasicus, Quenstedt. Petref. Deutschl., vol. v, p. 343, pl. exxxi, 
fig. 43. 
1883. Myrmercium pDEPREssuM, Sollas. Quart. Journ. Geol. Soc., vol. xxxix, 
p- 550. 
Sponges small, usually simple, though rarely two individuals are attached 
together ; discoidal, with rounded or sharp edges. The under surface may be 
either flattened, concave, or convex; it is covered by a rugose dermal layer. The 
upper surface is flattened or convex, with open grooves, simple or furcate, 
from *7 to 1 mm. in width, radiating from the central area. The central portion 
sometimes slightly depressed, with occasional oscules, and in the interspaces 
between the grooves there are circular canal apertures about °5 mm. wide. 
The fibres in transverse section are from ‘08 mm. to ‘15 mm. in thickness; they 
consist mainly of robust axial three-rayed spicules. The specimens are from 
5 mm. to 9 mm. in width, and from 2°5 mm. to 4°5 mm. in thickness. 
In form and surface characters the examples from the Inferior Oolite corre- 
spond so closely to the figures given by Quenstedt of a specimen from the Lias near 
Balingen, that, although unable to compare the minute structure, I think they may 
be considered to belong to the same species; and, as Prof. Sollas has pointed out, 
the form described by him from the Great Oolite under the name of Myrmecium 
depressum is equally similar, and may therefore be included as well. As, however, 
in this specimen there is no tubular cloaca, which according to v. Zittel is one of 
the essential characters of the genus Myrmecium, Goldfuss, it cannot properly be 
