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the genus Dipsas, and on the other with the genus Unio, connecting 
with U. Bengalensis, brought by Dr. Burrough from India, and 
described by me in the ‘Trans. Am. Phil. Soe.’ vol. vi. pl. 2. fig. 3. 
This peculiar form of tooth, if it may so be called, is peculiar to that 
part of the world, so far as my observation extends; for among the 
numerous species examined by me from Europe, Africa and America, 
South as well as North, I have never met with this character deve- 
loped as in those alluded to above. 
ANODONTA CREPERA. A. testd ellipticd, subcompressd, inequi- 
laterali ; valvulis tenuibus ; natibus subprominentibus ; epider- 
mide tenebroso-fuscd ; margarité vel albd vel purpured. 
Hab. Bongabon, Luzon, Philippines. 
Diam. 1:1; length 1:8; breadth 3°3 inches. 
Remarks.—Five of the six specimens under examination are purple, 
the sixth whitish. The outline is nearly oval. One of the specimens 
is obtusely biangular posteriorly ; the substance of the shell is slightly 
thickened anteriorly ; the beaks are too much eroded to observe any 
undulations ; the ligament is rather short and thin ; anterior cica- 
trices distinct ; dorsal cicatrices small, and placed in the centre of the 
cavity of the beaks. The species is closely allied to 4. tenuis, but is 
not quite so thin and is more transverse. Three specimens of the 
young have a well-defined anterior lamellar tooth and a distinct pos- 
terior raised line, which in the left valve is slightly divided. This is 
so marked in these young specimens, that one would scarcely hesitate 
to place them among the Uniones if we had not the adult, which have 
scarcely a vestige of the elevation on the dorsal line. 
ANoponTA TENUIS. A. testd ellipticd, compressa, inequilate- 
rali; valvulis pertenuibus ; natibus subprominentibus ; epider- 
mide tenebroso-fuscd. 
Hab, Sual, Luzon, Philippines. 
Diam. 1; length 1:7; breadth 3 inches. 
Remarks.—This is very closely allied to An. crepera herein de- 
scribed, and may, perhaps, when more specimens of the old and young 
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 erepera. 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. 
Anoponta suscrassa. A, testd oblongd, subinflatd, subequi- 
laterali ; valvulis subcrassis ; natibus prominentibus undula- 
tisque ; epidermide luteo-fuscd ; margaritd albidd, colore sal- 
monis tinctd et iridescente. 
Hab. Vaguna de Bai, Luzon, Philippines.- 
Diam. 1:2; length 1°7 ; breadth 2-9 inches. 
