347 



family XIV. Mactracea. 



" Oh ! who that has an eye to see, — 

 A heart to feel, — a tongue to bless. 

 Can ever imdelighted be. 



With Nature's magic loveliness !" 



Shells of this family are generally inequilateral, they are 

 either closed or gaping, and the ligament is always partially 

 or altogether internal. The following are its genera: — 

 Lutraria, Mactra, Gnatliodon, Crassatella, Mesodesma, Un- 

 gidina, Amphidesma, Cumingia. 



The shell of the Liitraria may be readily distinguished 

 by the absence of lateral teeth ; it has, also, a large sinus in 

 the muscular impression : its form is equivalve, inequilate- 

 ral, transverse, oblong or ovate, and gaping at the sides. 



Mactrce are very numerous, and include many rare and 

 beautiful species, their shells exhibit somewhat of diversity, 

 but are generally more or less triangular. The hinge is 

 characterized by a projecting triangular cardinal tooth in 

 each valve, with occasionally another thin sharp tooth on 

 the posterior side, and an elongated lateral one diverging 

 from each side of the umbo in one valve, fitting between two 

 similarly situated in the opposite valve. 



