PORIFERA OF THE L.M.B.C. DISTRICT. 207 
Our Clathria seriata fits in very well in Lendenfeld’s defi- 
nition of the Desmacidonide, and agrees also with the 
generic characters of Clathria as given by the same author, 
page 22: “Genus Cluthria—Desmacidonide with a 
skeleton composed of bundles of spicules invested by 
spongin, from which spined styli protrude.” One of 
Lendenfeld’s species of Clathria has chele (C. pyramida) 
and two have no chele, (C. macropora and C. australis). 
Therefore up to now there are four species of Clathria 
without chele, viz., C. australis, C. inanchorata, C. macro- 
pora, and C. serzata. 
The living sponge is of a dark blood-red colour, and 
encrusts the rocks with a layer of about 3 mm. in thick- 
ness. The skeleton consists of a network of horny fibres 
0°016—0'028 mm. thick. The meshes are square, and 
_0-09—0°225 mm. wide. In the axis of the horny fibres, as 
well as echinating from the fibres, smooth styli are found, 
01 mm. by 0:008 mm. The echinating styli generally 
stand together in bundles, and spring from the points 
where the fibres meet. According to Bowerbank toxa 
are very abundant in this species, but I found compara- 
tively few of them. ‘They measure 0°05 mm. by 0:001 mm. 
The oscula are numerous, and 1 to 1‘5 mm. in diameter. 
As I mention on page 208, this species is frequently found 
along with Plumohalichondria atrasanguinea, B. As these 
two species agree completely in colour, and as Pl. atra- 
sanguinea is decidedly the form which is best defended by 
the spicules, it might be regarded as a case of mimicry. 
The bright colouring of Pl. atrasanguinea would then be 
warning, and that of Clathria seriata protective. The simi- 
larity in colour may, however, be quite accidental. 
Plumohalichondria atrasanguinea, Bowerbank. 
Microciona atrasanguinea, Bowerbank. 
This form is new to our district, another species of the 
