234 BRITISH JURASSIC SPONGES. 
fibres, with here and there subcircular ostia. The specimen is 10 mm. in breadth 
by about 7 mm. in height; it has been sectioned horizontally, but the canal 
structure is not clearly shown. The width of the oscule and the absence of a 
basal epitheca in this specimen indicate that it does not belong to Spongites rotula, 
var. biretiformis, Quenstedt (‘ Petref. Deutschl.,’ vol. v, p. 234, pl. exxvi, fig. 6), to 
which it was referred by Prof. Sollas; but as Quenstedt’s species really comes 
under Myrmecium hemisphericwm, Goldfuss, the name proposed by Prof. Sollas for 
the present form will hold good. 
Distribution.—Inferior Oolite. Parkinsoni-zone in the Cliff at Burton 
Bradstock, Dorset. (Coll. Rev. G. F. Whidborne.) 
Genus.—LYMNORELLA, Lamourouw,'—emend., Hinde. 
1821. Exposition méthodique des genres de ]’ordre des Polypiers, p. 77. 
Syn.—Mammillopora, Bronn ; Lymnoreotheles, Fromentel ; Placorea, Pomel ; 
Inobolia, Hinde. 
Sponges massive, subglobular, irregularly nodose or branching; the individual 
spongites either completely amalgamated in a common stock, or projecting as 
conical, subcylindrical, or rounded forms, with tubular cloaca, giving off from the 
summit oscule short radiating horizontal furrows. In some instances the cloacal 
tube is not developed, and the spongites are only indicated by slight depressions 
here and there on the surface, with short open furrows radiating from them, and 
occasionally even these are not shown. The mode of growth is usually by a 
succession of concentric layers which overlap each other. 
The base of the sponge may be either concave, or there may be a short stout 
stem. In both cases the base is covered with a rugose dermal layer, which some- 
times extends over the lateral surface of the sponge.’ The surface which is not 
covered by the dermal layer either consists entirely of irregular pore-like 
apertures, bounded by the reticulate fibres, or, in addition to these, circular or 
stellate ostia. The fibres consist of axial three-rayed spicules (possibly also of four- 
rayed forms as well), enclosed by an outer layer of what is now almost wholly finely 
fibrous calcite. In this, fragments of filiform spicules and occasionally tuning- 
fork spicules are present. In one species, in place of the investing calcite layer, 
the fibres show definite filiform and three-rayed spicules. The typical species is 
Lymnorella mamillosa, Lamx., from the Calcaire a Polypiers (Forest-marble), near 
Caen. 
1 The name Lymnorea having been previously employed in 1809 by Péron et Lesueur for a 
genus of hydroid zoophytes, I propose to modify the term by using the diminutive “ella,” so that it 
can be retained for these sponges. 
