206 BRITISH JURASSIC SPONGES. 
Genus.—LEIODORELLA, Zittel. 
1878. Studien iiber fossile Spongien, II. Abhand]. der k. bayer. Akademie der 
Wiss., Cl. ii, Bd. xiii, Abth. i, p. 1138. 
Syn.—Planispongia, Tragos, Quenstedt (in part). 
Sponges with plate-like, ear-shaped, undulating walls, sometimes nodose or 
incrusting. Both surfaces of the wall covered with a smooth, apparently compact 
dermal layer which is perforated by oscules, and from these short curved canals 
extend into the wall and branch at their extremities. The skeleton consists of a 
moderately close mesh of spinous branching lithistid spicules with short simple 
axial canals. The dermal layer consists of small much-branched spicules. The 
typical species is Leiodorella expansa, Zittel, from the Upper Jura of Wodna, near 
Cracow. (‘ Studien,’ ui, p. 113, pl. ii, fig. 5; pl. im, fig. 11.) 
14. LeroporELLA contorta, Hinde, sp. nov. Plate XII, figs. 1, la. 
Sponge growing in the form of an irregularly undulating, somewhat fan- 
shaped expansion, about 90 mm. in width by 60 mm. in height, with walls from 
7mm. to1l0 mm. in thickness. The under surface is covered with a smooth dermal 
layer, which is penetrated by numerous irregularly disposed, sub-circular oscules 
from 1°25 mm. to 1°75 mm. in width and from 2 mm. to 3 mm. apart. The oscules 
do not now project beyond the surface, their margins are uneven, and they appear 
to serve as outlets for a variable number of canals, usually from two to four, which 
open into them. The upper surface of the sponge-wall is, to a great extent, 
concealed by matrix, but on grinding this away some sinuous horizontal canals are 
exposed, which may have extended beneath a dermal layer. The spicular mesh 
has been replaced by calcite, so that a thin section of the wall only shows a 
confused mass of interwoven spicules which form the fibres bordering the canals. 
In its appearance and general structure this sponge corresponds with some of the 
forms of Platychonia already described, but it can be readily distinguished from 
these by the smooth dermal layer with its numerous oscules. In the only other 
species of this genus yet described, L. ewpansa, Zittel, the oscules markedly project 
and they are less closely arranged than in the present form. 
Distribution.—Inferior Oolite. Parkinsoni-zone in the Cliff-section at Burton 
Bradstock. (Coll. G. J. Hinde.) 
