342 DISCOVERY REPORTS 



Duseideia tenuifibra, sp.n. (Plate LVI, fig. 8; Fig. 41). 



Holotype. B.M. 28. 2. 15. 840. 



Occurrence. St. WS 243 : north-east of Falkland Islands, 144-141 m. 



Diagnosis. Sponge lobate; surface minutely conulose; oscules 2-4 mm. diameter, 

 situated at or near ends of lobes ; texture soft, compressible ; colour, in spirit, greyish- 

 green; skeletal fibres very thin, o-oi4-o-02 mm. in diameter, forming an irregular net- 

 work of nearly quadratic mesh, with meshes subdivided by more slender fibres ; sand 

 grains not abundant, incorporated in fibres or lying loosely in meshes of skeleton. 



Remarks. The species is characterized by the slenderness of its fibres and by the 

 external form. The manner in which the included sand grains are held together is un- 

 usual. Instead of being entirely enclosed by the fibre, the grains are connected together 

 by short strands of spongin the ends of which are attached to the surfaces of the sand 

 grains (see Fig. 41 c). Near the base of the sponge, and in the inner parts of the lobes, 

 the fibres are thicker and the meshes of the skeleton reduced in size (cf. Fig. 41 ^). 



Genus Dendrilla, Lendenfeld 



Dendrilla membranosa (Pallas). 



(For synonynay see Burton, 1929, p. 448.) 



Occurrence. St. 45 : South Georgia, 238-270 m. 



Distribution. Wilhelm Land; Victoria Land; Graham Land; Australia; Indian 

 Ocean. 



THE AFFINITIES OF THE ANTARCTIC SPECIES OF 



TEDANIA, WITH NOTES ON THE DISTRIBUTION 



OF THE GENUS GENERALLY 



Of the six species of Tedania recorded on pp. 302-9 five resemble each other so closely 

 that their identification presents an unusual difficulty, but at the same time raises two 

 points of interest. The first of these points concerns the difficulty of classifying these 

 species ; and the second concerns the new importance of embryological observations in 

 systematic studies. Nearly 200 specimens of Tedcuiia were collected from the sub- 

 Antarctic and Antarctic and at first no satisfactory classification seemed possible. This 

 was largely due to the strong similarity in the shape of their spicules. Certainly, the 

 various specimens diff'ered in many ways and could be divided into five groups on the 

 basis of external form, but even then many intermediates could be found between the 

 typical forms of these five groups. Similarly, each group was characterized by a particular 

 range of spicule size, but here again intermediates could be found. It was, in fact, only 

 when the embryos were studied, and the data so obtained used as a starting-point for 

 the eventual classification, that it became possible to decide on the identification of 

 these specimens. 



