162 Mr. A. Dendy on the 



The ekeleton consists in the first place of an extremely 

 dense and tough, slender, cylindrical axis, measuring in the 

 branches about 0"6 millim. in diameter. This axis is com- 

 posed of a solid mass of rather dark amber-coloured spongin, 

 with numerous imbedded spicules. From it numeroua 

 primary fibres radiate upwards and outwards to the surface 

 of the sponge, joined together at right angles by secondary 

 fibres, so as to give rise to a very dense network with irregu- 

 larly rectangular meshes. Both primary and secondary fibres 

 contain a large proportion of spongin. The primary fibres 

 terminate at the surface in dense^ elongated tufts of spicules 

 arranged in a typical Axinellid manner, amongst them being 

 a very great number of the strongly spined styli. The very 

 long, slender styli, projecting far beyond the surface and 

 forming so characteristic a feature of Raspailia fruticosa, are 

 not present, and it seems very probable that they are func- 

 tionally replaced by the numerous spined styli, which, it must 

 be remembered, are very rare in the preceding species. 



Spicules : — (1) Smooth, very gradually sharp-pointed, 

 more or less curved styli (PI. XII. fig. 1 J), usually short 

 and stout, measuring about 0*28 by 0'014 millim., but often 

 longer and slenderer and sometimes shorter and stouter ; 

 in short, very variable in size : these spicules form the 

 main mass of the skeleton. (2) The spined styli (PI. XII. 

 fig. 1 a) ; more or less curved, stout, and tapering gradually 

 towards the apex. The spines are very stout and sharp- 

 pointed and strongly recurved towards the base, which is 

 usually quite smooth ; commonly the spicule terminates in 

 three or four large spines arranged around the projecting apex 

 like the teeth of a grapnel, the apex itself being represented 

 merely by a low rounded wart ; or sometimes the spicule may 

 terminate in a sharp-pointed apex with no spines. Size of 

 spicule about 0'025 by 0*0094 millim. These spicules are 

 very abundant in the position indicated above. In boiled- 

 out preparations a few very much elongated, slender, smooth 

 styli, like those occurring at the surface of Raspailia fruti- 

 cosa, make their appearance ; but I have not observed them 

 in situ. 



I have much pleasure in naming this species after Mr. 

 Thurston, to whom I am indebted for the opportunity of 

 studying and describing this valuable collection. It is 

 interesting to find two species so nearly resembling one 

 another in all essential characters, yet so totally distinct from 

 one another, as Raspailia fruticosa and Raspailia Thurstoni, 

 both coming from the same locality. They may be distin- 

 guished from one another immediately both by their external 



