128 
with much obliquity and the anterior lob© strongly 
marked ; the sides of the straight hinge frequently have 
teeth, or crenulations, similar to those that often occur 
in common Oysters ; besides the principal muscular im- 
pression in each valve, there is a smaller one near the 
hinge, which is much more conspicuous than in any 
Oyster I have observed it in : this has not escaped 
the notice of the Artist who drew the excellent figures 
for Cuvier and Brogniart’s Geology of the environs of 
Paris. 
Found in Chalk wherever it occurs, and not confined 
to the upper beds. It is also met with in the Chalk 
Marl. Lamarck’s unfortunate repetition of this species, 
under two genera has made it adviseahle to give it an 
entirely new name ; the specific name vessicularis, too 
nearly resembles vessiculosus, which has been used else- 
where (see tab. 369) rather inadvertently, but it is 
to be hoped appropriately. Brogniart’s quotation of 
G. dilatata, M. C. 149, it is hardly necessary to observe 
is quite erroneous, that species never occurs in Chalk. 
Our specimens are mostly from Norwich, through the 
kindness of the Rev. G. R. Leathes ; this is the same 
place that furnished Smith with the specimens figured 
in his work upon Strata identified by Fossils. 
The Genus Podopsis, to which Lamarck has referred 
this shell, was established by De France, and ap- 
pears to include the same shells with Dianchora of Min. 
Conchology ; in fact his Podopsis striata, is the Dian- 
chora lata of Min. Conch, tab. 80. which being taken 
from an inferior specimen, was probably overlooked ; the 
characters of the two Genera are of course the same : the 
shell before us having no opening in the beak cannot be 
a Podopsis. 
