BIVALVIA. VG 
been a little too much improved at the umbo, and it is difficult in its present condition 
to say whether it belongs to Mytilus or Modiola. Its present name is merely 
provisional. 
16*. Mopioza suscarinata? Lamarck. Tab. XIX, fig. 20. 
At page 71, Tab. XII, fig. 9, is figured and described a shell from the London Clay 
at Highgate, and referred with doubt to Lamarck’s species from the Paris Basin. 
Mr. Edwards has since obtained a specimen from Barton, with the general characters 
of the French species, although differing in some minor particulars, and I have thought it 
desirable that it should be represented. In comparing our present specimen with the 
figure of the Paris Basin species, there appears a difference in the length of the hinge-area, 
and also in the direction of the margins, both the dorsal and ventral margins being more 
curved in the French shell than in our own; there is also a slight difference between 
the Barton specimen and the one previously figured from Highgate, which has a more 
prominent or subcarinal projection, with the umbo rather more terminal. 
Our shell is covered with elevated or rather imbricated lines of growth, and these are 
more distant upon the siphonal region than upon the other parts of the shell ; they appear 
as if they once supported a fringed epidermis like that which ornaments the shell which 
has been called J. darbata. 
Since the above was written and the figures engraved, I have seen a specimen in the 
cabinet of Mr. Prestwich of the following dimensions :—3} inches in length, with a height 
or breadth of 1 in., and a tumidity of an inch and half: this was obtained at Clarendon 
Hill, near Salisbury, and I presume it to be the same as MW. subcarinata from Highgate. 
24. Mopioza supcanceLLata, Edwards, MS. Tab. XIX, fig. 15. 
Locality. Barton (Edwards). 
An imperfect specimen has recently come into the possession of Mr. Edwards, to 
which is attached the above specific name. It bears considerable resemblance to two 
species from the Paris Basin, viz., Mod. Rigaultii, Desh. (‘ An. sans vert. du Bass. de Paris, 
t. 1, p. 29, pl. 74, figs. 23, 24), and Mod. Levesquei (id., p. 30, pl. 75, figs. 4, 5); our 
shell appears to approach rather nearer to the latter, and, if the specimens themselves 
could be compared, might possibly be referred to that species; there are, however, some 
differences which may be here pointed out. The Barton shell does not appear to have 
been so broad or so high as that of the French species, neither has it so long an area for 
connexus; the dorsal edge is finely but deeply denticulated, as that of IZ Levesquei is 
. also represented to be, but it does not appear so much curved as in the latter. There 
