18 Messrs. G. S. Brady and D. Robertson on the 
of his kind assistance in the prosecution of our researches in 
the Fen-district. 
Candona diaphana, nov. sp. (Pl. V. figs. 1-3.) 
Carapace of the male (?), as seen from the side, elongated, 
subreniform ; greatest height situated behind the middle, 
and equal to less than half the length ; obtusely and evenly 
rounded in front, obliquely behind ; superior margin highest 
at the posterior third, thence sloping almost in a right line 
and with a very gentle declivity forwards, very steeply and 
with a slightly concave curve backwards; inferior margin 
gently sinuated. Seen from above, compressed, tapering 
equally and rather suddenly to the extremities, which are 
pointed; sides subparallel; width scarcely equalling one- 
third of the length. The hinge-margin of the left valve is 
suddenly produced towards each extremity into a very con- 
spicuously overlapping curve, the posterior being much 
larger than the anterior. Shell-structure as in the preceding 
species. Length =; inch. 
Hab. Ormesby Broad, and the river Nene at Peterborough. 
e specimen only from each locality. From the com- 
pressed outline and very pronounced characters of the shell, 
we suppose this to be probably the male. The limbs are not 
sufficiently preserved to indicate the sexual character through 
the shell. . 
Candona hyalina, nov. sp. (Pl. IX. figs. 5-8, and 
Pl. V. figs. 4-11.) 
male more compressed; seen from the side, the inferior 
margin more deeply sinuated ; superior margin excessively 
elevated and gibbous in the middle, behind which it sud- 
denly dips and zm steeply backwards with a marked 
concave curve, ell-structure as in the two preceding 
species. Superior antenn: sparingly setose, last two joints 
of nearly equal length, about twice as long as broad, the 
rest shorter and thicker; inferior melee Cae of any 
proper setose brush, the place of which is occupied in the 
