72 



CONCHIFEKA. 



Pinna (Linn.). Shell wedge-shaped, horny, fra- 

 gile ; truncate behind ; the beaks forming a point 

 in front ; hinge toothless. Animal with the man- 

 tle-edge doubly fringed ; foot long, grooved, spin- 

 ning a powerful silky bissus. 



P. pectinata. Fig. 114 ; J n. s. 



Avicula (Brug.). Wing-shell. Shell wedge- 

 shaped ; the hinge-line straight, prolonged at the 

 sides into wing-like processes ; hinge-teeth one or 

 two, minute. 



A. tarentina. Fig. 115 ; J n. s. 



115 



FAMILY IV. OSTEEAD^E. 



Shell unequal- valved, nearly equal-sided, often 

 adhering to other bodies by one valve ; epidermis 

 inconspicuous ; beaks central ; ligament internal ; 



