OF CONCHOLOGY. J "7 9 



SCIENTIFIC INTELLIGENCE. 



On the Anatomy of Tridacna Elongata. By M. Leon 



Vaillant. 



"Tridacna elongata, Lam., occurs very abundantly in the 

 Bay of Suez, where it is often employed as food. The author 

 has accordingly been able to examine a great number of indi- 

 viduals of this animal. 



"The retractor muscle of the foot, which is of considerable 

 size in proportion to the protractor, serves, in part, for the 

 closure of the valves; hence it may be that in those Monomy- 

 ary Acephala which have an adductor muscle distinctly di- 

 vided into two parts, the upper portion is to be regarded as 

 representing the retractor of the foot diverted from its normal 

 functions. The byssus of the Tridacna, already described by 

 Miiller, consists of two parts — one adhering to the bottom of 

 a cavity of the foot, the other uniting this with external 

 bodies. Each of these is secreted by a distinct organ — the 

 former by the bottom of its cavity, the latter by a collection 

 of racemose glands lining a circular groove in the wall of the 

 cavity. The large notches of the margins of the shells enabled 

 the author to ascertain the force which the mollusk is capable 

 of exerting. He fixed an individual by one of its valves, and 

 suspended a weight to the other. In this way he found that 

 a specimen 21 centimetres in length, of which the valves 

 weighed 1.264 kil., could support a weight of 4.914 kilo- 

 grammes; so that it may be supposed that an individual 

 weighing 250 kilogrammes, and these are not uncommon, 

 might, at a given moment, put out a force of more than 900 

 kilogrammes. 



"In the nervous system, the branchial ganglia, forming a 

 single mass with no trace of longitudinal division, exhibit 

 transverse furrows bounding two false circumvolutions, A 

 sort of inelastic tendon accompanies the connective extended 

 from the branchial ganglion to one of the buccal ganglia 



