214 BRITISH JURASSIC SPONGES. 
form fresh branches, and sometimes again subdivide. 'The individual spongites 
are either subcylindrical, club-shaped, or ovoid, usually with a slight inflation at 
the summit, which is rounded, with a circular, well-defined cloacal aperture, usually 
from 1 to 1°5 mm., but sometimes 2 mm. in width. The colonies range from 
25 to 63 mm. in width, and from 25 to 58 mm. in height ; the spongites are from 
3 to 6 mm. in thickness; just before division takes place some stems are 8 mm. 
in thickness. 
The outer surface is only covered by a dermal layer in a narrow band wrap- 
ping round the bases of the stems and buds, and in certain places where there 
are indications of renewals of growth; the rest of the surface merely shows small 
oval or irregular apertures, bounded by the skeletal fibres, which at the surface are 
flattened. The wall fibres are comparatively stout, ranging from *12 to °33 mm. in 
thickness ; they are composed of medium and small three-rayed spicules, perhaps 
also some four-rayed, very closely intermingled together (Pl. XIV,fig.1c). Therays 
vary from ‘05 to °22 mm. in length. The peculiar minute tuning-fork spicules are 
also present in the fibres (Pl. XIV, fig. 1d). The outer portion of the fibres in 
some cases consists of a thin layer of filiform sinuous spicules, and occasionally 
similar spicules form a lining to the fibres bounding the cloacal tube. 
There is considerable latitude both as regards the mode of growth and the size 
of the colonies and the individual spongites in the examples of this species, but 
there are so many gradational links that it is necessary to include all in one 
species. Both large and small spongites occur in the same colony, and on the 
same base may be found both cylindrical and club-shaped forms. Also in some 
colonies the stems diverge and extend outwards, whilst in others they are nearly 
upright and subparallel with each other. 
This species appears to be very abundant in the Great Oolite, and a very 
fine series of specimens obtained from this formation at Hampton Cliffs near Bath 
are now in the Woodwardian Museum at Cambridge. The type of Peronidella 
repens, Sollas, is a fragment of a specimen of P. pistilliformis. 
Distribution.—Great Oolite, Hampton Cliffs, near Bath ; Stroud; Forest-Marble, 
Winsley, near Bath (E. A. Walford); Cornbrash, Langton Herring, near 
Weymouth. 
Also in the ‘ Couche a polypiers,’ at Langrune, Lebisey, Ranville, near Caen, 
France. 
