BIDDULPHIA. AMPHITETRAS. 51 



GOMPHONEMA, 

 From gompJius (a wooden peg), 



is shaped like a wooden peg or wedge, and grows like a 

 tree, on long filaments, attached to confervse or stones in 

 fresh water, varying in shape, being sometimes round at 

 the tip, or notched, or with a plain edge. 



LICMOPHORA, 



From likmos (a fan), and phora (bearing), 



grows likewise on a stalk, but in dense masses, and is 

 a marine diatom, parisitic on seaweeds. Its growth is 

 different from that of the Gomphonema. The stalk widens 

 in the process of multiplication, and so spreads out the 

 frustules like a fan. 



RHABDONEMA. 

 From rhabdos (a staff). 



These are marine also, and used as test objects, because, 

 besides the striations, each frustule has two or four rows 

 of marks called vittse. They were joined together when 

 alive, forming a long tube ; but usually we only see the 

 separated frustules here. 



GRAMMATOPHORA MARINA. 

 From gramma (a letter). 



This is used as a test object to discover some very delicate 

 striae on the borders of each valve, and is also remarkable 

 for its vittse, which resemble letters; especially this G. 

 marina, which has four Greek gammas (y) on each frustule. 

 The vittae are internal siliceous folds, and distinguish a 

 large section of the Diatomaceee. There are fifteen species 

 of Grammatophora. This one is found on seaweed in the 

 Atlantic and Pacific oceans. 



BIDDULPHIA. AMPHITETRAS. 



Biddulphia is one of the chain-like diatoms which adhere 

 to one another by projecting angles, or horns. A band of 



