Invertebrate Gallery of the Indian Museum. 15 



i.— CALCISPONGIiE. 



Ill the Calcispongix the sponge skeleton is made up of 

 spicules of carbonate of lime interlaced to form a sort of 

 rigid felt-work. 



The Calcispongise are represented in the collection by 

 specimens of Ascetta, Sycon, Sycandra, Grantessa, and 

 Leucandra. 



2. PORIFERA NON-CALCAREA. 



[Cases 1—3]. 

 In the Non-Calcarea the skeleton consists either of spi- 

 cules of silica (flint), or of horny fibres. There are three 

 Orders — Hexactinellida, Chondrospongi^, and Curnacu- 

 spongise. 



ii.-PORIFERA HEXACTINELLIDA. 



[OTasc 1]. 



Hexactinellida (Glassy or Flinty Sponges), in which 

 the skeleton consists of spicules of flint or opal. The 

 Hexactinellida^ which are well represented in the Museum 

 collection, live almost entirely in the great depths of the 

 ocean. They very rarely occur in less than 100 fathoms, 

 but are to be found at all depths between 100 and 3,000 

 fathoms. 



In the Indian Sea they have been found at the greatest 

 depth at which the dredge has been used by H. M. I. 

 M. S. ^^Investigator'' and according to the observations of 

 the naturalists of this vessel they occur in the greatest 

 abundance in the neighbourhood of the Andaman Islands 

 at depths of 180 to 300 fathoms. 



The skeleton in the Hexactinellida is formed of spicules 

 of flint or opal which are typically six-rayed, the tips of 

 the rays of neighbouring spicules being very commonly 

 cemented together by flint to form a lattice-work of re- 

 markable regularity, symmetry, and rigidity. This is well 

 seen in the beautiful Venus' Flower Basket {Euplectella), 



