46 A MONOGRAPH OF THE 



Society/ vol. i, p. 563, where, under the head of Alcy- 

 onium, it is simply recorded as "A. cydonium. Island of 

 Fulah and Unst." Dr. Pleming, in his ' History of British 

 Animals,' p. 517, has described the sponge, and has 

 changed the specific name into a generic one, and given it 

 a new specific one, designating it Cydonium Mulleri. Dr. 

 Johnston, in his ' History of British Sponges,' has correctly 

 referred the sponge to Lamarck's previously established 

 genus Gcodia ('Anira. S. Vert.,' 2nd edit., ii, p. 593), 

 but has changed the specific name to Zetlandica, apparently 

 from being satisfied that Muller's Alcyonium cydonium was 

 really A. diyitatum-oi Ray and Linnaeus, 



I am much indebted to Dr. Fleming for kindly sending 

 me the type specimen for examination. It is an irregular, 

 tuberous mass, the greatest diameter of which is two and a 

 half inches, with several large and deep depressions, one of 

 which is an inch across, and three fourths of an inch in 

 depth, forming, when it stands on the cut base, a deep 

 arched cavern in its substance. On each side, near the 

 base of the walls of the cavern, there is a single large 

 osculum, the eighth of an inch in diameter, and one of them 

 has the membrane closing it ^remaining in a partial state 

 of contraction, protruding, and exhibiting a central orifice 

 about one sixth of a line in diameter, and near the greater 

 one there is an irregular group of smaller oscula, and a few 

 others, similar to^the latter, are visible in the other depressed 

 portions of the sponge. The true base of the sponge has 

 been destroyed. In some of the natural depressions on 

 the surface of the sponge there are the remains of large 

 fusiformi-acuate spicula, those protected portions of the 

 surface having evidently been quite hirsute with them. 

 The upper portion of the specimen is thickly studded with 

 minute stellate depressions or pits ; this pitting of the sur- 

 face is caused by the contraction and depression of the 

 dermal membrane, immediately above the distal orifices of 

 the intermarginal cavities. Dr. Johnston says of the* crust 

 that it is " dimpled in some places with numerous pores 

 placed pretty closely together, and large enough to be visible 

 with the naked eye." These orifices are not the pores, but 



