Jones— Orbitoides of Malta and West Indies. 103 
discoidal Foraminifera belonging to the genus Orbitoides.* 
Where weathering has affected the stone, it has become porous, 
its brown colour has changed to yellowish-grey, and the struc- 
ture of the Orbitoides has become perfectly distinct; the walls 
of the numerous chamberlets remaining, as a skeleton, free from 
the infilling of subtranslucent, greyish-white carbonate of lime 
that obscures them in the stone. Dilute acid also removes the 
calcite, and clears the framework of the Orbitoides, showing 
even the canal-system of these shells. 
Much of the weathered superficies, moreover, is roughened 
by the removal of exposed parts of the Orbitoides, furrows 
and hollows being left, which show the weathered edges of 
remaining parts of the organisms at the bottom of the holes. 
The weathered surface also is smooth and undulated in patches 
continuous with some of the now imperfect Orbitoides, and 
showing where these had formerly lain. One of these undu- 
lating Orbitoides is thus traceable over a space of at least 24 
by 12 inches; and no indication exists of any part of its former 
circumference. It has an apparently uniform thickness (where 
it can be measured) of 7,th inch; and other fragments seen in 
section in the stone are of the same thickness (or less, with 
smaller width). 
Besides the thin broad specimens, there are some small 
biconvex Orbitoides with expanded edges, about 4+ inch wide 
and jth inch thick at the centre; also a few Nummuline, 
small and biconvex, with sharpish edge, some measuring ;,th 
by sth inch, and some being rather larger. I have also 
detected the section of a Globigerina ; and fragments of Echino- 
derms and Bryozoaf also appear in this flint. 
Some, at least, of the small biconvex Orbitotdes seem to 
belong to O. dispansus, Sowerby; some are probably the 
young of the larger flat form, or small individuals with rela- 
tively large primordial chambers.{ This large thin Orbctocdes 
is of considerable interest, especially for two reasons,—firstly, 
it belongs to that species of Orbitoides which is characterized 
by having vertical partitions to its central layer of chambers, 
and these more or less cylindrical—namely, O. Mantelli, 
or less perfectly converted into flint, which, at its outer limit, imperfectly replacing 
the particles of the chalk, marl, or shell-mass, ends with a rough surface. 
* See Dr. Carpenter's ‘Introd. Study Foram.’ (Ray Soe.), 1862, p. 298. 
+ The network of the weathered Orditoides first attracted attention as some- 
what resembling Bryozoan structure. 
¢ As in Nummulina, so also in Orbitoides, there may be seen individuals that, 
commencing with a relatively large central or first chamber, never attain a large 
discoidal growth, whereas others that begin with a small primordial chamber have 
a very much greater peripheral development. 
