338 



THE OCEAN WORLD. 



These molluscs are found in every sea on the globe, and under all 

 latitudes. Many of them belong to our own and the French coasts, 

 where they are eagerly sought for by collectors, as well as for food. 

 The flesh of the animal, however, is coriaceous, and little esteemed. 

 The species most common on the littoral of the Atlantic is Cardium 

 edulis (Fig. 147), its white or fawn-coloured shell being hollowed out 

 into six and twenty furrows, forming so many corrugated ripples on 

 its side. 



Cardium costatum (Fig. 148) is an exotic species which inhabits 



Fig. 148. Cardium costatum (Linuanis). 



the coast of Guinea and the Senegal, the shell of which, white and 

 fragile, is much sought after by collectors. 



The thirteenth family of our table, Tridacnidre, consists of only eight 

 or ten species, but it contains the largest of all, the giant Tridacna. 

 The historian of the wars of Alexander the Great speaks of oysters 

 inhabiting the Indian Ocean which were more than a foot long ; these 

 were probably Tridacna, the shells of which were most likely to be 

 seen by the Macedonian conquerors. The valves of Tridacna gigas 

 are sometimes found a yard and a half in length, and weighing five 

 hundred pounds. Magnificent examples may be seen in the church of 

 Saint Sulpice, Paris, where they hold the holy water. These beauti- 

 ful shells were the gift of the Venetian Kepublic to Francis I. Under 

 Louis XIV., the cure Languet had them presented to the church of 

 Saint Sulpice, where they are used as fonts for holy water. Another 

 pair are exhibited in the church of Saint Eulala, at Montpelier, but 

 much smaller in size. The shells of Tridacna are formed, as repre- 

 sented in PL. XVII., of three acute angles, festooned on their edges 



