XV. NOTES ON FRESHWATER SPONGES. 



By N. Annandai^e, D.Sc, F.A.S.B., Superintendent , Indian 



Museum. 



No. XV. — Sponges from shei^ls of the genus Aetheria. 



The curious shells of the genus Aetheria ( " Freshwater Oys- 

 ters," as Reeve has aptly called them) offer on their roughened 

 and often corrugated surface a favourable nidus for the growth of 

 sponges, while the fact that, like the true oysters {Ostrea), they 

 are firmly fixed by the lower valve to solid bodies, renders them 

 still more suitable in this respect. The genus is confined to tropi- 

 cal Africa and is represented in the collection of the Indian 

 Museum by only two lots of shells, one of which is labelled as 

 being from the Nile, while the other is of uncertain provenance. 

 The former represents a form of A. caillaudi, Fer., the species to 

 which the latter, which has been examined by Mr. H. B. Preston, 

 also in all probability belongs. This species is found only in the 

 basin of the Nile, from which the first of the two sponges here 

 described certainly and the second probably, therefore, comes. 



At least one freshwater sponge {Corvospongilla loricata, Welt- 

 ner) has already been described from a shell of Aetheria, and I 

 have little doubt that others would be discovered in the same 

 position if a careful examination were to be made of the shells of 

 this genus already preserved in museums. 



The only Indian species of the family Aetheriidae {Mulleria 

 dalyi, Smith) is found in the tributaries of the R. Kistna. It was 

 originally described from Mysore and has recently been collected 

 in the Western Ghats by Mr. F. H. Gravely. I have examined 

 specimens from both localities, but, although the shells closely 

 resemble those of Aetheria in external characters, I can find on 

 them no trace of either sponges or polyzoa. 



Spongilla (Eunapius) aetheriac, sp. nov. 



Sponge. — Only the basal part of the sponge remains and even 

 from it all but the gemmules and their dense cage of spicules has 

 disappeared. It was, however, evidently an encrusting form. 



Skeleton. — All that remains of the skeleton is a dense but 

 quite irregular network of macroscleres enclosing the gemmules. 

 No trace of spicule fibres can be detected in it. 



Spicules. — The skeleton-spicules are smooth, slender, sharply 

 pointed amphioxi, on an average about 0'296 mm. long by o"or36 

 mm. in greatest transverse diameter. The gemmule-spicules 



