OF THE FAMILY OF NAIADES, 445 



be double in the right; lateral tooth lamelliform and double 

 in the left valve only, the two teeth form one continuous 

 curve line, somew^hat abrupt at both terminations, more so 

 at the anterior one ; anterior cicatrices distinct ; posterior cica- 

 trices confluent; dorsal cicatrices very perceptible. Cavity 

 of the beaks wide and very shallow ; nacre purple and irides- 

 cent. 



Remarks. — This beautiful shell most resembles the Sym- 

 phynota alata in its general form, but its posterior wing is less 

 elevated. The colour of its nacre is the same. It differs 

 entirely, however, in the cardinal tooth, and in possessing the 

 anterior connate wing. A metallic sound is produced by 

 dropping one valve into the other, which is very remarka- 

 ble, and is caused by the density of the calcareous matter of 

 the nacre, which is very thin. The epidermis is exceedingly 

 smooth and glossy. 



2. Symphynota Bi-alata. Plate XIV. fig. 24. 



Testa ovato-triangulari, inmquilaterali, transversim rugosd, sub-ven- 

 tricosd ; margine dorsali bi-alatd ; valvulis teniiibus, ante et post nates 

 connatis ; natibus et ala. posterioris basi apiceque undulatis ; natibus 

 haud prominentibus ; dente lamelliformi unico in valvuld utrdque; liga- 

 ment o celato; margaritd tenuiet iridescente. 



Shell triangular-ovate, inequilateral, transversely wrinkled, sub-ven- 

 tricose; dorsal margin raised into two wings; valves thin, connate before 

 and behind the beaks ; beaks and the base and summit of the posterior 

 wing undulated ; beaks not prominent; one lamelliform curved tooth in 

 each valve ; ligament concealed; nacre thin, pearly, and iridescent. 



Hab fresh waters of the south of Asia ? Brought 



from Canton by Captain Barr. 



My Cabinet. 

 Cabinet of Mr Pierpoint. 



Cabinet of Mr Hyde. 

 Cabinet of Mr Phillips. 



