236 BRITISH JURASSIC SPONGES. 
Massive sponges, spherical, hemispherical, or irregular in form, supported on 
a short stout pedicle, or having the under surface concave and covered with a 
wrinkled dermal layer. The rounded upper surface may be either nearly even or 
with slightly projecting conical or rounded eminences. The oscules at their 
summits are about 1 mm. in width, and short open horizontal furrows, about 5mm. 
wide, radiate from their margins. The oscules serve as the apertures of straight 
tubes or cloaca which extend through the sponge, but they are interrupted at 
intervals by transverse floors, which mark the different layers of growth (Pl. XVIII, 
fig. 2). The general surface is covered by numerous subcircular ostia about 
°3 mm. in width, bounded by very fine reticulate fibres. The ostia apparently 
connect with incurrent canals, which, however, cannot be distinguished in the 
interior of the sponge from the spaces between the skeleton fibres (Pl. XVIII, fig. 
2a). The skeleton fibres are delicate, from -08 mm. to ‘16 in thickness: the 
three-rayed axial spicules are usually in single series ; their rays range up to °24 
mm. in length by ‘039 mm. in thickness. Tuning-fork spicules are also present. 
The sponges are very variable in size; small specimens are not more than 
15 mm. in diameter, whilst large forms reach 63 mm. in length by 40 mm. in 
breadth and height. As a rule the specimens from the Inferior Oolite are larger 
than those from the “ Caleaire 4 Polypiers”’ at Ranville, near Caen. The brief 
description and poor figures of this species given by Lamouroux leave con- 
siderable doubt as to its real characters. This author states that the upper 
surface is “ finement lacuneux et sans pores visibles,” which seems to imply that 
there are no ostia, as in the Inferior Oolite specimen here figured (Pl. XVIII, 
fig. 2). But in some of the examples from the original locality near Caen, now in 
the British Museum, which otherwise closely correspond with the description of 
L. mamillosa, there are ostia plainly shown ; whilst in others not so well preserved, 
only the fine apertures between the fibres are visible on the surface, and thus 
the presence of ostia appears to me to be a character of the species. 
Distribution.—Inferior Oolite. Pea-grit series; Murchisonx-zone, Crickley 
Hill, Ravensgate Hill, near Cheltenham (Mr. R. F. Tomes, Mr. F. Longe); 
cutting on the Midland and South-West Junction Railway, east of Andoversford 
(Mr. E. Wethered) ; Oolite-Marl, Birdlip Hill, near Gloucester (Mr. R. F. Tomes). 
Also in the Calcaire a Polypiers at Les Moustiers, Ranville, Luc, &c., near Caen, 
France. 
44. Lymnoretta inctusa, Hinde. Plate XVIII, figs. 3—3 d. 
1883. Inosousa tnctusa, Hinde. Cat. Foss. Sponges, p. 185, pl. xxxv, figs. 2, 2 a, 2b. 
Sponges massive, turbinate, subspherical, or in irregular nodose masses. 
