190 
UNIO antiquus. 
TAB. DXCIV.—^g’s. 3. 4. & 5. 
Spec. Char. Transversely ovate, elongated, com- 
pressed ; back and front nearly parallel and 
straight; anterior side small. 
Length half the width. The anterior side is larger in 
this than in U. porrectus, and the general form is more 
square. Fig. 3. exhibits the usual character of casts. 
Fig. 4. has the substance of the shell remaining, but con- 
verted into spar. Fig. 5. is from a cast that is more 
pointed than usual, and approaches to U. porrectus, of 
which it is even possible that it may be the young shell. 
The commonest species in the Sandstone of Tilgate 
Forest in the Weald Clay. 
UNIO aduncus. 
TAB. DXCV.— /g. 2. 
Spec. Char. Wedge-shaped, gibbose, antiquated ; 
anterior side straight, small ; the opposite ex- 
tremity more or less produced, truncated, and 
bent downwards ; shell very thick. 
The straight anterior extremity and concave margin of 
the front are striking characters. Length generally ex- 
ceeding half the width, but variable. 
Not very uncommon in the same formation as the last : 
it seems to be the species figured by Mr. Mantell in his 
Fossils of Tilgate Forest, p. 57. pi. 10. f. 11. 
