HOLCOSPONGIA. 225 
the fibres, and their outlines are very difficult to distinguish in thin sections. 
Smaller sinuous spicules are present in some of the fibres, but not recognisable 
in others. In the specimens examined the spicular structure is not well 
preserved. 
There is very great diversity of form and size in the sponges referred to this 
species, but after careful study of a large series of specimens I feel obliged to 
unite them together, as in the canal system and in the character of their fibres 
they are closely similar, and there are numerous transitions between the extremes 
of the series. The simplest form met with is an ovate specimen, about 10 mm. in 
length and breadth, growing attached to a fragment of shell. It has a tubular 
cloaca, and the walls are deeply scored with sinuous furrows (Pl. XVI, fig. 4). In 
another specimen there are several similar individuals united together into a small 
colony (fig. 4a), and completely amalgamated ; whilst in others the individuals in 
the colonies may be either partially attached or free from each other except at their 
bases (figs. 4b—e). The iargest colony is about 50 mm. in breadth and height, 
and the spongites from 7 mm. to 9 mm. in diameter. The specimens are for the 
most part completely weathered out from the matrix, so that the fibres and the 
canals are shown very distinctly. . 
Distribution.—Great Oolite. Hampton Cliffs, near Bath. The type-specimens 
are in the Woodwardian Museum, Cambridge (Walton Collection). 
Genus.—Hotcosronata,’ Hinde, gen. nov. 
Sponges simple or growing in colonies. The individual spongites are spherical, 
hemispherical, subcylindrical, club-shaped, or discoidal; in the compound forms 
they are sometimes completely amalgamated with each other. The base of the 
colony and, in some instances, the lateral surfaces of the spongites are usually 
covered with a rugose dermal layer. Summits rounded or flattened, with a 
central area, which may or may not be depressed, in which a variable number of 
excurrent canals open. From the central area a number of open furrows extend 
over the summit and down the sides of the sponge, and with these furrows canals 
from the interior communicate. 
The skeleton fibres form an open tissue; they consist of fairly large amal 
three- and in some instances four-rayed spicules enclosed by marginal filiform 
spicules, probably three-rayed. The dermal layer consists of an agglomeration of 
three- and perhaps of four-rayed spicules of various dimensions, which are closely 
felted together. 
7 'OXkos, a furrow. 
