The Indian species fall into seven genera, one of which (Spongilla) consists of three subgenera. With one exception (that of Pectispongilla, which has only been found in Southern India) these genera have a wide distribution over the earth's surface, and this is also the case as regards the subgenera of Spongilla. Four genera (Heteromeyenia, Acalle, Parmula, and Uruguaya) that have not yet been found in India are known to exist elsewhere.
Five of the Indian species are known to occur in Europe, viz., Spongilla lacustris, S. crateriformis, S. carteri, S. fragilis, Trochospongilla pennsylvanica; while Ephydatia meyeni is intermediate between the two commonest representatives of its genus in the Holarctic Zone, Ephydatia fluviatilis and E. mülleri. Of the species that occur both in India and in Europe, two (Spongilla lacustris and S. fragilis) are found in this country in forms sufficiently distinct to be regarded as subspecies or local races. Perhaps this course should also be taken as regards the Indian forms of S. carteri, of which, however, the commonest of the Indian races would be the typical one; but S. crateriformis and T. pennsylvanica seem to preserve their specific characters free from modification, whether they are found in Europe, Asia, or America.
The freshwater sponges of Africa have been comparatively little studied, but two Indian species have been discovered, S. bombayensis in Natal and S. alba var. cerebellata in Egypt. Several of the species from the Malabar Zone are, moreover, closely allied to African forms (p. 11).
Fossil Spongillidæ.
The Spongillidæ are an ancient family. Young described a species (Spongilla purbeckensis) from the Upper Jurassic of Dorset (Geol. Mag. London (new series) v, p. 220 (1878)), while spicules, assigned by Ehrenberg to various genera but actually those of Spongilla lacustris or allied forms, have been found in the Miocene of Bohemia (see Ehrenberg's 'Atlas für Micro-Geologie,' pl. xi (Leipzig, 1854), and Traxler in Földt. Közl., Budapest, 1895, p. 211). Ephydatia is also known in a fossil condition, but is probably less ancient than Spongilla.
Ehrenberg found many sponge spicules in earth from various parts of the Indian Empire (including Baluchistan, Mangalore, Calcutta, the Nicobars and Nepal) and elsewhere, and it might be possible to guess at the identity of some of the more conspicuous species figured in his 'Atlas.' The identification of sponges from isolated spicules is, however, always a matter of doubt, and in some cases Ehrenberg probably assigned spicules belonging to entirely different families or even orders to the same genus, while he frequently attributed the different spicules of the same species to different genera. Among his fossil (or supposed fossil) genera that may be assigned to the Spongillidæ wholly or in part are Aphidiscus, Spongolithis, Lithastericus and Lithosphæridium, many of the species of these "genera" certainly belonging to Spongilla and Ephydatia.
Oriental Spongillidæ not yet found in India.
Few freshwater sponges that have not been found in India are as yet known from the Oriental Region, and there is positive as well as negative evidence that Spongillidæ are less abundant in Malaysia than in this country. The following list includes the names of those that have been found, with notes regarding each species. It is quite possible that any one of them may be found at any time within the geographical boundaries laid down for this 'Fauna.' I have examined types or co-types in all cases except that of Ephydatia fortis, Weltner.
I. Spongilla (Euspongilla) microsclerifera*, Annandale (Philippines). P. U.S. Mus. xxxvii, p. 131 (1909).
This sponge is closely related to S. lacustris, but apparently does not produce branches. It is remarkable for the enormous number of microscleres in its parenchyma.