CONCHIFERA. UNIMUSCULOSA. 45 



by a hinge or a ligament ; sometimes there are 

 accessory pieces to the valves. 



" Some of the ConcJiifera are furnished with a 

 kind of foot, which enables them to move with 

 their shells, to draw out fibres by which they 

 fasten themselves to marine bodies. The mus- 

 cles that fasten the animals to their shells are 

 thick and strong ; their use is, to close th^ valves 

 by contracting ; when the muscle is relaxed, the 

 elastic ligam^ent is sufficient to open them. The 

 Conchifera are all aquatic ; some inhabit fresh 

 water, the others dwell in the sea. 



" The class contains nineteen families and 

 two orders. The first order, Bimusculosa, con- 

 tains thirteen families. The first includes genera 

 that you will scarcely expect to find among the 

 bivalve shells. 



" 1st Family, Tulicolaria, contains, 



Asperg ilium, Watering-pot .. Serpula. 



Clavagella 



Firtaluna 



Septaria Serpula. 



Teredina Fossil genus. 



Teredo Teredo. 



" Aspergillum Javanum is a rare and curious 

 shell from the Indian seas, (Plate 9.) The 

 whole family is remarkable, and was referred, 



