50 THE ELEMENTS 



apertures in the sand ; when the tide 

 has receded, they may be easily found 

 by looking for these marks. 



The French writers have divided 

 the Tellina into three genera : Tellina, 

 Cyclus, and Pandora. 



In Turton's Linne ninety-four spe- 

 cies are described : twenty-two spe- 

 cies have been discovered in Britain. 



Genus 7th.— CARDIUM,(acockle.) 

 Animal a Tethys ; shell bivalve, nearly 

 equilateral, equivalve, generally con- 

 vex, longitudinally ribbed, striate or 

 grooved, the margin dentated ; hinge 

 with two alternate teeth in the mid- 

 dle, near the beak ; one of them com- 

 monly incurved ; and larger remote 

 lateral teeth on one side, each looking 

 into the opposite. Linn. Syst. 306. 

 Plate 5th, hV 7th. 



Habitation. The Cardium, with 

 the exception of one species, have only 

 been found to inhabit the ocean ; this 

 species, the Cardium Fluviatile, has 



