THE CHARACTERS OF THE DEEP-SEA FAUNA 83 



In the first place bathybial fish, mollusca, crnsta- 

 cea, and other animals usually possess a remarkably 

 small amount of lime in their bones and shells. 



In fishes we are told that the bones have a fibrous, 

 fissured, and cavernous texture, are light, with 

 scarcely any calcareous matter, so that the point of 

 a fine needle will readily penetrate them without 

 breaking. In some the primordial cartilage is 

 persistent in a degree rarely met with in surface 

 fishes, and the membrane bones remain more or 

 less membranous or are reduced in extent, like the 

 operculuni, which is frequently too small to cover 

 the gills. 



This cannot be due in all cases to a deficiency of 

 carbonate of lime in the sea water, for we find these 

 characters well marked in some of the fish, such as 

 Melanocetus Murrayi, Chiasmodus rtiger, and Osmodus 

 Lowii, that are found on the Globigerina mud. 



Then again, the shells of the deep-sea Lamelli- 

 branchs, Gasteropods, Brachiopods, and Crustacea 

 are very frequently remarkably thin and transparent, 

 a character that is probably more generally due to 

 a weakness in absorptive or secretive activity than 

 to a deficiency in the supply of lime. 



There are one or two characters of the deep-sea 



G 2 



