230 BRITISH JURASSIC SPONGES. 
The skeleton is an open meshwork of fibres; the main lines running between 
the grooves are 3 mm. in thickness in transverse section, and the smaller fibres 
about ‘12mm. The spicular structure is not very distinctly shown ; the rays of 
the larger axial spicules are about °33 mm. in length by ‘08 mm. in thickness. 
Sinuous marginal spicules are only slightly developed. 
These sponges vary considerably in size ; small individuals are not more than 
5 or 6 mm. in height and breadth, whilst the largest examined is 22 mm., and the 
average about 12 mm. in height and breadth. The thickness of the wall-plate does 
not usually exceed 3°5 mm. 
This species is very common in the sponge-bed at Shipton Gorge; it is readily 
distinguished by its mode of growth and the grooved character of the under 
surface. The specimens are now all free, but they were originally attached to 
other bodies, and one of the forms shows on its basal expansion an imprint of the 
cruciform spicules of a Hexactinellid sponge. 
Distribution.—Inferior Oolite. Parkinsoni-zone at Shipton Gorge, and in the 
Cliff-section at Burton Bradstock, near Bridport, Dorset. (Mr. EH. A. Walford ; 
G. J. Hinde.) 
38. Hoxcosponeia contorta, Hinde, sp. nov. Plate XVII, figs. 4—4 d. 
Sponges small, usually simple, but occasionally two individuals are attached at 
their bases, spherical, hemispherical, or club-shaped, with a flattened or corrugated 
base. The front surface, and in some forms the summit of the sponge, has from 
five to six short open grooves or furrows, from *4 to “6 mm. in width, radiating 
star-like from a centre, and bounded by thickened ridges of spicular fibre. These 
erooves are sometimes contracted to merely oval depressions or oscules, which open 
into the interior of the wall. The top of the sponge is rounded and sometimes 
furrowed transversely. ‘The surface opposite to that with the stellate grooves 
has sometimes slight furrows, or exhibits merely pore-like interspaces between the 
fibres; not infrequently the entire surface, with the exception of the stellate 
portion, is covered by a rugose dermal layer, composed of agglomerated three- and 
four-rayed spicules of various dimensions; the rays of the larger forms, which are 
very distinctly shown in some parts of the surface, ranging up to *2 mm. in length, 
whilst in a small spicule they are not more than ‘03 mm. (Pl. XVII, fig. 4d.) 
The sponges for the most part are about the size and shape of peas, varying 
from 3 to 6°5 mm. in diameter. A few exceptional forms are club-shaped, and 
from 5 to 18 mm. in height. As a rule they are now free, but they appear to have 
grown by a flattened base on pieces of shell and other organisms. In most of 
