Zoological Society. 495 



of both species are compared, prove only to be a variety. The spe- 

 cimens before me, however, differ in the tenuis being rather thinner 

 and less elliptical, the outline inclining to oblong. The existence of 

 teeth in the young, and the rudiments on the dorsal line in the adult, 

 are very similar to the crepera. Of the four specimens before me, 

 two have the nacre purple and two white. The beaks are too much 

 eroded to observe any marks of undulations. The ligament is rather 

 long and thin. Anterior cicatrices distinct ; dorsal cicatrices small, 

 and placed in the centre of the cavity of the beaks. 



Anodonta subcrassa. A. testd oblongd, subinjlatd, subcequi- 

 laterali ; valvulis subcrassis ; natilus prominentibus undula- 

 tisque ; epidermide luteo-fuscd ; margaritd albidd, colore sal- 

 monis tinctd et iridescente. 



Hab. Laguna de Bai, Luzon, Philippines. 



Diam. 12 : length 1*7 ; breadth 2'9 inches. 



Remarks. — It is rare to meet with an Anodonta of the thickness of 

 this species, but it still is not so ponderous as the arcuata, Fer., or as 

 lato-marginata (Nobis). It cannot be confounded with either of these 

 species, not being arcuate, and not having compressed beaks like 

 the former, and being oblong and thinner than the latter, as well as 

 also being destitute of the broad margin. The substance of the shell 

 is slightly thickened anteriorly, and the basal margin is emarginate ; 

 the beaks are submedial, and when perfect are beautifully ornate 

 with numerous small folds which.form an acute angle from the point 

 of the beaks, nearly parallel to the line of the umbonal slope ; the 

 ligament is short and rather thick ; anterior cicatrices distinct; dorsal 

 cicatrices large, and placed in the cavity of the beaks. The colour of 

 a single young specimen before me is salmon inclining to purple, and 

 the adults have the cavity of the beaks tinted in this manner. In the 

 young specimen the lamellar line on the dorsal margin is very well 

 denned, in the adults this character is nearly obliterated. 



Anodonta Cumingii. A. testa ellipticd, co?npressd, incequilate- 

 rali; valvulis subcrassis ; natibus vix prominentibus ; epidermide 

 atro-fuscd; margaritd alba et iridescente. 



Hab. Malacca. 



Diam. 1 ; length 1*9 ; breadth 3 inches. 



Remarks. — This is an interesting species, and remarkable in the 

 form of the dorsal line, which is thickened and raised immediately 

 under the beak, where it is slightly incurved. This disposition to 

 form a curve tooth reminds us of that group of Naiades which M. 

 D'Orbigny discovered in the rivers of South America, and which 

 comprise his genus Monocondylcea. In fact, this species forms a 

 perfect link between the Anodontce and his genus, and it is allied very 

 closely to that species of this group which I described in the * Trans, 

 of the Am. Phil. Soc.' vol. viii. pi. 18. fig. 39, under the name of 

 Margaratina Vonderbuschiana, from Java. The form of the tooth 

 of the 31. Bonellii also approaches to these. The anterior margin of 

 the Cumingii is rounded, the posterior is somewhat biangular ; the 

 anterior cicatrices confluent ; the dorsal cicatrices form a line across 



