BRITISH SPONGIADiB. 



275 



Colour. — Alive, lilac colour. Rev. A. M. Norman. 

 Dry state, light fawn yellow. 



Habitat— Yni\y of Forth, Dr. Grant. Peterhead, Mr. 

 Peach. Chudleigh Salterton, Rev. A. M. Norman. 



EsDamined. — In the dried state. 



This sponge is apparently a rare species. Dr. Grant 

 states that he had met only with a single specimen from 

 the Prith of Forth, and Dr. Johnston describes the speci- 

 men from which he drew up his character as containing a 

 piece of Zostera marina, from which he infers it is a littoral 

 species. I have been unable to detect the Zostera marina 

 in any of the specimens at the British Museum. 



In the Johnstonian collection of British sponges in the 

 British Museum there are four small specimens arranged 

 on one board, which are labelled Halichondria cinerea. 

 Two specimens are upon one piece of card marked 17°, 

 and the other two are respectively marked 17" and 17^. 

 On examining each of them carefully I found them to be 

 four distinct species of the genus Isodictya of this work, 

 with two of which, one of those marked 17", and the one 

 marked 17°, I was previously acquainted; the remaining 

 two specimens, one marked 17°, and the other 17^, were 

 new to me ; under these circumstances I found it was im- 

 possible to decide which of the four was the type of the 

 sponge designated by Dr. Grant as Spongia cinerea. I 

 therefore at once applied to that learned natuvaHst to assist 

 me to a correct determination of the species in the event of 

 its having been preserved in his cabinet : fortunately this 

 was the case, and he responded to my request by kindly 

 sending me a portion of the type specimen described in his 

 works. On carefully comparing its structural characters 

 with those of the four specimens marked Halichondria 

 cinerea in the Johnstonian collection, I found that the one 

 marked 17° was identical in structure with the type speci- 

 men in the cabinet of Dr. Grant. 



In the dried condition of the four, sponges thus ex- 

 hibited in the national collection, it would be impossible to 

 distinguish the species by the unassisted eye ; but a close 



