302 



POPULAR CONCHOLOGY. 



opening, sometimes secretes unequal chalky pieces. — A 

 few species. 



These shells are brought from the Indian Ocean, where 

 they attain so large a size that a single person can with 

 difficulty carry one valve, and some, indeed, have been 

 said to weigh 500 lbs. In Roman Catholic countries, the 

 shells are sometimes used as receptacles for the holy water 

 in the churches, and formerly they were considered suf- 

 ficiently valuable to form a present to a monarch, those in 

 the church of St. Sulpice at Paris having been presented 

 to Francis the First by the republic of Venice. The 

 animal is correspondingly large, and it has been stated 

 that more than one hundred persons could make a meal 

 upon that which inhabits the Tridacna gigas : this may 

 be an exaggeration, but there is no doubt the architect of 

 so extensive a dwelling must be exceedingly large.* The 

 Tridacna adheres to the rocks by a stout and strong 

 byssus with so much tenacity as to require the aid of 

 a hatchet to separate it. A specimen of this shell, 

 brought from Sumatra, is now in Arno's Vale, Ireland, 

 and weighs 507 lbs., each valve being four feet six inches 

 in length, and two feet five and a half inches in breadth. 

 The interior of the shell is of an opaque white, and very 

 beautiful. 



Layard found one species of this genus in the ruins he 

 visited in the East ; he remarks : — " Amongst them," 

 (the relics found at Wiorka in Mesopotamia) " and de- 

 serving particular notice, are the fragments of a shell 

 ( Tridacna squamosa) on which are engraved the heads of 

 two horses, apparently part of a subject representing a 

 warrior in his chariot. The outline upon them is not 



* The valves are so large as probably to require centuries to com- 

 plete their growth. Reeve's Conchologia Systematica. 



