85 
CORBULA nitida. 
TAB. CCCLX1L — Figs. 1, 2, and 3. 
Spec. Char. Ovate, subtrigonal, equilateral, 
gibbose, anteriorly truncated, smooth ; valves 
nearly equal. 
A thin shell, most gibbose towards the beaks, which 
are somewhat produced ; the young individuals are 
rather pointed on the sides ; the old ones oval, with a 
small truncature anteriorly ; the surface is smooth, often 
shining, and the valves very nearly equal : length rather 
more than half the width. 
Very small, not exceeding three-tenths of an inch in 
width : the almost perfect equality of the valves is re- 
markable, but the form of the hinge is exactly that of the 
genus Corbula, from which it cannot conveniently be 
separated. 
First observed with the following, by Professor Sedg- 
wick, in several parts of the Isle of Wight, below the 
upper fresh-water formation. 
Figs. 2 and 3 are magnified representations. 
CORBULA cuspid ata. 
TAB. CCCLX1L — Figs. 4, 5, and 6. 
Spec. Char. Transversely oblong, tumid, in- 
equivalved, subequilateral ; anteriorly ca~ 
rinated and cuspidated ; lower margin of the 
left valve expanded and inflected. 
A thick blunt-edged shell, whose anterior side is 
obliquely truncated, and defined by a ridge that ends in 
a projecting point on the margin 5 the lip-formed edge of 
