No. 8. MACTRA. 

 Kneading-trough. Inhabitant a Tethys. 



Shell bivalve, inequilateral, valves equal, middle tooth of the hinge compli- 

 cated with a small hollow on each side, and lateral remote teeth inserted into 

 each other. Twenty-seven of this species are described by Grewelin (Maxrga 

 signifies a kneading trough; but the resemblance to this article in any one of 

 the Mactrs is very slight,) and the number of species now known amounts to 

 forty-two. 



These are generally found at the mouths of rivers, immediately beneath 

 the surface of the sand, or among substances that have been thrown up, and 

 left by the sea. The prevailing color is a bluish or yellowish white. One 

 kind is used as food by the common people at Dartmouth, Devonshire, Eng- 

 land. 



The genus Mactra possesses little beauty or variety, and a similarity of 

 coloring and form pervades the whole. 



DIVISION I. 



Family 1st. 



Scientific name. 



Spengleri, 



Carinata, 



Maculata, 



Corallina, 



Lactea, 



Cinerea, 



Locality. 

 Cape of Good Hope. 

 Mediterranean. 

 Nicobar Isles. 

 Mediterranean, Guinea. 

 Tranquebar. 

 Britain. 



Scientific name. 

 Stultorum, 

 Grandis, 

 Achatina, 

 Triangularis, 

 Minutissima, 

 Donaciforrais, 



Locality. 



Britain. 

 New Jersey. 



do. 

 Britain. 



do. 

 Ceylon. 



Family Id. Having a striated or wrinkled surface. 



Striatula, 



Plicataria, 



Papyracea, 



Vitraea, 



Cygnea, 



Turgida, 



Violacea, 



Cuneata, 



Rotundata, 



Glabrata, 



Nitida, 



West Indies. 

 Indian Ocean. 

 Nicobar Isles. 

 Ceylon. 

 Tranquebar. 



do. 



do. 



do. 



African Ocean. 



Striata, 



Radiata, 



Solida, 



Solidissima, 



Truncata, 



Sub-truncata, 



Australis, 



Piperata, 



Tenuis, 



Boysii, 



Britain. 



do. 

 North America. 

 Britain. 



do. 

 New Zealand. 

 Mouth of the Niger. 

 Britain. 



do. 



