R. W. H. ROW—REPORT ON THE SPONGES : NON-CALCAREA. ont 
sponge. The spicules which occur in them are very numerous, frequently 
lying 10- to 20-serially, and frequently being arranged in a slightly plumose 
fashion. Between these main fibres secondary fibres occur, forming a 
connecting meshwork ; in these fibres the spicules are usually uniserial, but 
may be 2- or 3-serial. Rarely they are altogether absent from the fibre. 
The spicules are small, straight oxea, abruptly pointed at each end; they 
measure on an average 0°08 mm. in length and 0-002 mm. in diameter. 
The colour in spirit is grey-brown. 
Locality. Suakin Harbour. 
Distribution. Red Sea, West Indies. 
SPINOSELLA INCRUSTANS, n. sp. (Text-fig. 13.) 
This new species has been created for the reception of a single specimen of 
rather small size, consisting of four very low and wide tubes. Two of these 
tubes face laterally and are almost wholly fused into one, only the oscula at 
their summits being separate. The specimen measures in all 75 mm. long, 
40 mm. broad, and the tubes vary in height from the base from 15 mm. to 
25mm. This highest point occurs on the tubes facing laterally. Hach tube 
possesses an osculum at the summit, and these vary in diameter from 3 mm. 
to 6 mm. 
The surface of the sponge is covered with small low conuli, whose average 
height is 2 mm. and which are usually 4 mm. to 5 mm. apart. In some parts, 
however, the conuli are much smaller and fewer, and in some parts hardly 
visible at all. They indicate the ends of the main skeletal fibre. 
The colour of the specimen varies in different parts from light brown to dark 
red-brown, and purplish at the summits of the tubes. 
The texture of the sponge is very firm, almost hard, and incompressible. 
Skeleton arrangement. 
The skeleton is a regular reticulation of spicule-covered spongin-fibre, with 
a fairly rectangular mesh which averages 0°4 mm. to 0°6 mm. wide in most 
parts of the sponge. There can be distinguished primary and secondary 
fibres. In the primary fibres the spicules lie 3- to 4-serial, and the fibres run 
radially. The secondary fibres contain only one row of spicules, and 
occasionally are entirely without spicules. They run both radially and 
tangentially in the sponge. ‘These secondary fibres can be divided into large 
and small fibres. The large are nearly as thick as the primary, measuring 
0-1 mm. in diameter, while the small are much thinner than the primary 
fibres, and only measure from 0:015 mm. to 0:02 mm. in diameter. 
The dermal membrane contains a very delicate reticulation of spongin-tibre, 
in which spicules are rather scanty, only one or two here and there. In size 
they are similar to the small secondary fibres. 
