t;0 DESCRIPTIONS OF 



towards the basal margin. The folds on the wing also differ, the Gumingii having 

 the row from the beak to the posterior margin irregular and indistinct,- and much 

 nearer to the umbonial slope, which is slightly carinate. The folds in the superior 

 part of the wing are small and scarcely more than irregular curves along the edge. 

 This shell is very much compressed at the beaks, and reminds one of the Margariiana 

 complmiata. The long lateral teeth are very remarkable, they are perfectly lamellar, 

 like the blade of a knife^ and rise straight and abruptly from the plain of the disk. 

 The cardinal teeth are inclined downwards and are irregular. The folds on the side 

 and on the posterior slope are very distinctly marked within ; those of the sides 

 enlarging into distant low undulations to the basal margin. The cicatrix, which is 

 superior to the gre^t anterior cicatrix, is not placed, as is usual in this genus, at the 

 immediate end of the cardinal tooth, but on the plain of the disk, a short distance 

 behind that tooth, and perfectly distinct from it and the other two cicatrices. The 

 position of the pallial cicatrix is very remarkable. In the anterior part it is three- 

 fourths of an inch from the margin, and in the posterior portion one and three-fourths 

 of an inch distant. It is the most beautifully rayed shell I am acquainted with, being 

 furnished all over the whole disks with closely set, dark green rays, on a yellowish 

 ground. Mr. Cuming, to whom I owe the possession of two fine specimens, received 

 them from the northern part of China., and I dedicate it to him who has done- so much 

 to develope the knowledge of the Molluscs from a large portion of the globe. 



Unio Shanghaiensis. pi. 30, fig. 121. 



Testa Ixvi, vald^ transversa, valde insequilaterali, inflata, cylindraoea, posticfe subbiangulata ; valvulis 

 crassiusculis, antice crassioribus ; natibus subprominentibus, ad apices corrugatis et plicatis ; epider- 

 mide tenebroso-oliva, nitida, obsolete radiata ; dentibus cardinalibus parviuseulis, compressis, crenu- 

 latis, rectis, in utroque valvulo duplicibus; lateralibus praelongis, lamellatis rectisque ; margarita. 

 argentea et vald^ iridescente. 



Shell smooth, very transverse, very inequilateral, inflated, cylindrical, somewhat 

 biangular behind ; valves somewhat thick, thicker before ; beaks rather prominent, 

 corrugated and folded at the apex; epidermis very dark olive, shining, obscurely 

 radiate ; cardinal teeth rather small, compressed, crenulate, straight, double in both 

 valves; lateral teeth very long, lamellar and straight; nacre silver white and very 

 iridescent. 



Unto Shanrjhaiensis, Lea. Proc. Acad. Nat. Sci., 18.59, p. 153. 



Hah. — Shanghai, China. H. Cuming. 



My cabinet and cabinets of Mr. Cuming and Mr. Wheatley. 



Diam. -7, Length 1, Breadth 2-2 inches. 



Shell smooth, very wide, very inequilateral, inflated, cylindrical, somewhat bian- 

 gular behind and regularly rounded before, flattened on the sides and subemarginate 

 at base ; substance of the shell somewhat thick, thicker before ; beaks rather promi- 



