56 Journal of the Mitchell Society [December 



styles. And yet this is what the recent definitions of the genus do, 

 with the result that Dendy's definition (1905, p. 172) would exclude 

 forms that are admissible on the definition of Vosmaer (loc. cit.) or of 

 Hentschel (1911, p. 381), and vice versa. Of course the difficulty is 

 well known. It is a difficulty offered everywhere by nature. 



A considerable number of species, over thirty, have been referred 

 to this genus, A good many of them are excluded by Pick in his essay 

 on Raspailia (1905). He would deUmit the genus somewhat more 

 narrowly than is intended in this paper. Taking R. viminalis as a 

 standard, some of the chief divergencies within the genus may be 

 enumerated. It is to be regretted that in a number of the old species 

 the data given do not permit a decision with regard to several of the 

 features. 

 Habitus. 



The long, slender, cylindrical habitus, "whip-like" in Ridley and 

 Dendy's terminology, branching or not, is common. But it is de- 

 parted from in a numl)er of species. For example, while the habitus 

 is branching and subcylindrical, the branches are comparatively short 

 and stout in several of the Dictyocylindrus (Raspailia) species de- 

 scribed in Bowerbank's British Sponges, in R. ramosa and R. pumila 

 e. g. In R. paradoxa Hentschel (1911, p. 381), the habitus departs 

 widely from the typical, the sponge consisting of several somewhat 

 flattened lobe-like divisions, which arise together from a common base 

 and expand above. Again in R. irregularis Hentschel (1914, p. 121) 

 the habitus deviates markedly from the typical, the sponge being club- 

 shaped. 

 Skeleton. 



The axinellid type of skeletal framework consisting of an axial 

 column and radiating fibres may be thought of as constant in Ras- 

 pailia. Deviations from the pi'ecise form of skeletal framework found 

 in R. viminalis are however common among the species that have been 

 referred to this genus. Some of them may be enumerated as follows: 

 In R. (Syringella) clathrata Ridley (1884, p. 461) the radial fibres are 

 thick, not reduced as in R. viminalis. In R. (Syringella) australiensis 

 Ridley (loc. cit. p. 460) also the radial fibres are thick and project at 

 the surface, but the surface tufts are not said to be of the R. vimi7ialis 

 type. In R. (Syringella) rhaphidophora Hentschel (1912, p. 371), the 

 radial fibres are represented by lamellae. In R. hifurcata Ridley (loc. 

 cit. p. 459) a radial fibre and dermal tuft are together represented by a 

 long style or a tuft of long styles which project at the surface (a more 



