ex of the inner, gr structureless layers. It is from half a 
illim a to more than a millimeter in thicknese, the epidermis 
resting directly upon it. “Except i in very old specimens, this layer 
constitutes the whole thickness of the shell for the width of a 
couple of millimeters from the margin, and in very young speci- 
mens it agent prone about half the space between the mar- 
gin and the pallial lin 
The prismatic Re eA may be (pe bags st the naked eye and 
can be well studied by the use of o lles’s $ inet Ball a3: 
enses. Under this magnifier the fee pens of the marginal 
border is seen to be fin ely granular, each granule being ‘the con- 
vex end of one of the prisms which gain A layer. These 
ruption, re reminding one in their Fae ee ayes of certain 
species of Chetetes. But viewing the prisms upon their ends they 
are seen to vary insize much more than the cells of Chetetes do, 
and consequently to lack that uniformity in cross section, presented 
by the coral. 
Naiades were fossilized unter the same circumstances 
an 
as thin a shell as Myalina and Inoceramus now 
Mr. ek’s abee aia s he scones that the prismatic 
structure is a very ¢ nstant rages of the 
fossil Aviculide, and ti is doubts “of is 2 as a famil 
character; but since it is also seen in certain gloss of Mytilide 
and the Naiades, it] is known that it is not the peculiar property 
of any family. 
Note on “ Cone in cone ;” by C. A. Waurrz, M.D. (Commu- 
nicated for this Journal.)—The structure known as “cone in cone” 
is quite common in the calcareo-carbonaceous 
sua 
somewhat concretionary layers, from four to ty incl 
the apices of the cones pointing "downward. Being much interested 
in the views advance 
rin So 
with the opinion that the peculiar structure in question was produ- 
ssure upon the coneretionary mass while it was forming. 
A. plcgle 3 of examples were found there which presented the cone- 
like 
structure radiating from a center, the apices of the cones all 
ting to that center. The concretiofs were imbedded in the 
common dark shales of the Coal-measures, the Pad one being 
about two and a half feet in transverse diame 
3: 
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