161 
thickness I have observed in any shell within the same 
extent of surface ; some parts near the edge being almost 
half an inch thick, while others near the beaks (only 
three or four inches distant) are as thin as card-paper. 
For several fine illustrative specimens of this species, 
mostly too large to figure even in a quarto plate, I am 
indebted to C. B. Rose, Esq. : they are from the Upper 
Chalk of SwafFham and West Lex ham, Norfolk. Fig. 1. 
is taken from a pair of shells, filled with flint, that was 
bought at Mr. Parkinson’s sale. Fig. 2. is from a por- 
tion of the flatter valve picked out of a Chalk-pit at 
Bury St. Edmonds by the Rev. J. Holme, M.A. F.L.S. 
The inequality of the valves of this shell, which can- 
not be separated from Inoceramus, proves the impro- 
priety of forming two genera. 
While the above was in the press, I received the spe- 
cimen represented at fig. 3. from the Rev. G. R. Leathes. 
It came from the Bury Chalk. 
INOCERAMUS gryphssoides. 
TAB. DLXXXIV.— fig. 1. 
Spec. Char. Ovate, ventricose, concentrically un- 
dulated ; valves unequal, the smallest gibbose; 
beaks incurved, pointed, approximated. 
So nearly does this resemble I. concentricus, that, ex- 
cept size and the close beaks, we can see no marked dif- 
ference ; yet few persons would be induced to consider 
them the same species. 
From the Green Sandstone west of Lyme Regis, in 
Dorsetshire. Large pearly fragments also occur in Blue 
Marie at Ringmer in Sussex, which are probably the 
same species. It is too gibbose for either I. tenuis or 
I. Cripsii, — our specimens of which are not perfect 
enough to describe. 
