PORIFEHA OF THE L.M.B.(!. DISTllICT. 1>07 



Onr Clathria seriata fits in very well in Lendenfeld's defi- 

 nition of the Desniacidonidao, and agrees also with the 

 generic characters of Claihrin as given by the same author, 

 page 22: "Genus Clathria — Desmacidonidse with a 

 skeleton composed of bundles of spicules invested by 

 spongin, from which spined styli protrude." One of 

 Lendenfeld's species oi Clathria has choidd {C. pjjramida) 

 and two have no chelae, (C. macropora and C. australis). 

 Therefore up to now there are four species of Clathria 

 without chelae, viz., C. australis, C. inanchorata, C. macro- 

 'pora, and C. seriata. 



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. w4de. In the axis of the horny fibres, as 

 well as echinating from the fibres, smooth styli are found, 

 0*1 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 PI. atra- 

 sanguiiiea 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 



