CONCHIFERA. 



259 



The Conchifera may be classed in accordance with 

 the folio win o- Table : — 



f Having the mantle open, and without tubes or OSTRACEA. 

 special apertures Oysters. 



f 





Not p r o- 

 longecl so 

 as to form 

 tubes. The 

 mantle 



"< 



Prolonged so 

 as to form 

 tubes. The 

 mantle 



Open in front and having' 



but one separate aperture I MYTILACEA. 

 for the escape of etfetel Mussels, 

 matter 



Closed and pierced by three) 

 apertm-es, the iii-st of 

 which serves for the 

 passage of the foot, the! 

 second for respiration, f 



espn 



and the third for the exit | 

 of excrementitious mate- [ 

 rials J 



r Open in front and present-) 

 in 2: two tubes behind . ( 



Closed and having in froiit j 

 or below only a single j 

 Oldening for the passage of 

 the foot, and two tubes 

 behind 



CHAMACEA. 



Clams. 



CARDIACEA. 



Cockles. 



INCLUSA. 



Borers. 



The first family of the Conchifera includes Oysters 

 ( Ostracea) ; these have no foot, and the mantle is 

 entirely open; the shell is irregular, thick and 

 foliated, and is generally fixed to some foreign body 

 by the outer surface of one valve. The hinge is 

 toothless, and the ligament is internal. 



The Common Oyster. " The living luxury " is too 

 well known to need description. 



The Tree Oyster (Ostrea arbor ea), which in Africa is 

 met with clinging in clusters to the exposed roots of 

 the mangrove-trees that fringe the margin of all the 

 great rivers in tropical climates, is, according to 

 Adanson, as delicate and well tasted as our own. 

 The negroes lop off a branch loaded with the shells, 



