452 On the Characters of [Aug. 



Symphynota Bilineata. Plate XL fig. 19, of ditto. 

 " Testa subellipticd, transversa, incequilaterali, compressd ; valvulis tenuis, 

 simis ; posteriori margine dorsali elevatd connatdque ; natibus subprominulis, 

 undulas concentricas et duas lineas elevatas ad marginem posteriorem cur. 

 rentes, habentibus ; dentibus cardinalibus laminatis et in valvuld dextrd solum 

 duplicibus ; lateralibus rectis ; margaritd colore salmonis subtinctd. 



" Shell subelliptical, transverse, inequilateral, compressed ; valves very- 

 thin ; posterior dorsal margin elevated and connate ; beaks very slightly 

 elevated, concentrically undulate and possessing two elevated lines which 

 pass to the posterior margin ; cardinal teeth lamelliform and double in 

 the right valve only ; lateral teeth straight ; nacre slightly salmon co- 

 loured. 



Hab. River Hoogly, Hindostan, G. W. Blakie. 

 Diam. -3, Length *7, Breadth T3 inches. 



" Shell subelliptical, transverse, inequilateral, compressed, diaphanous ; 

 substance of the shell extremely thin ; beaks very slightly elevated, con- 

 centrically undulated, possessing two small elevated lines which pass 

 (posterior to the umbonial slope) to the posterior margin ; valves elevated 

 into a carina and connate in the posterior dorsal margin : dorsal margin a 

 right line ; ligament very small ; epidermis shining, greenish yellow, 

 darker on the posterior slope ; cardinal teeth lamelliform and double in 

 the right valve only ; lateral teeth lamelliform, long and straight ; pos- 

 terior and anterior cicatrices both confluent ; dorsal cicatrices obsolete ; 

 cavity of the beaks shallow, very wide, and exhibiting the undulations of 

 the beaks ; nacre very thin and slightly salmon coloured, darker in the 

 cavity of the beaks. 



" Remarks. — This very small species was brought from Calcutta by Mr. 

 Blakie, with the U. caeruleus (Nob.). Both were procured about one 

 hundred miles above that city. It resembles, in its outward characters, 

 the young of S. cygnea ( Anod. cygnea, authors). It is, however, more 

 transverse, and differs altogether in the formation of the hinge, which is 

 furnished with perfect cardinal and lateral teeth. In the peculiar cha- 

 racter of the double tooth in the right valve, it resembles the S. ochracea*. 

 The bilineata is easily distinguished by the two delicate lines which pass 

 from the beaks to the posterior margin." 



Note. — This species, which is tolerably abundant in the tank on the 

 skirts of the southern glacis of Fort William, is an Unio to all in- 

 tents and purposes. Mr. Lea's genus Symphynota is founded on an 

 adventitious character which is incidental to most of the winged 

 bivalves. It culls from various genera, such, as Unio and Anodon, 

 (already well separated on the best of all distinctive characters for 

 bivalves, the difference of the teeth,) species, which otherwise agree 

 with their respective genera, to unite them in one unnatural group. 

 Mr. Lea's apology for its introduction, viz. the difficulty of defining 



* See vol. iii. p. 455. 



