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Miscellaneous. "7 
previous observations on the change of tint which the infusoria that 
colour our salt marshes undergo by age. These animalcules, which 
are white at their birth, become green in their middle age, and do 
not till their adult age take the purple tint which makes them so re- 
markable. In general the green infusoria are not so often seen as 
the red in salt marshes, which seems to indicate that these monads 
remain but a short time in their middle state. 
We have found the same infusoria in the argilo-calcareous marls 
which are found at Cardona beneath the rock salt. There they have 
their beautiful purple tint, but they are in too small numbers to com- 
municate it to the mass of marl which has remained grayish. ‘This 
fact also proves, that in the ancient world, as in the present one, the 
animalcules were precipitated after their death to the bottom of the 
waters in which they previously lived.—Comptes Rendus, Mar. 16. 
ON THE GENUS PUPINA. BY JOHN EDW. GRAY, ESQ. 
The shell of this very curious and interesting genus has been 
placed by different authors in very different parts of the system, 
some persisting that it should be arranged with the marine genera 
on account of the grooves on the left side of the mouth. From a spe- 
cimen which Mr. Powis has very kindly given to me, I have no 
doubt in my own mind that it is a very distinct genus of Cyclosto- 
mide, for this specimen has a horny orbicular many-whorled oper- 
culum as large as the mouth of the shell, exactly resembling the 
opercula of some of the genera of that family. The polished surface 
of the shell and the form of the notch is very unlike any that I have 
hitherto observed among the shells of marine mollusca. The latter 
is peculiar, as being funnel-shaped, wider outwards, and narrowed 
into a slit within, and only appears as a narrow simple groove on 
the outer surface of the peristome. 
I am acquainted with two species of this genus ; one Pupina fusca, 
small, pale brown, with a yellowish white peristome ; and the other, 
Pupina grandis, twice the size of the former, more ventricose, and 
of a bright yelk yellow colour; there is a fine specimen of the latter 
species in the cabinet of Mr. Stainforth. I suspected that this genus 
should be referred to the family of Cyclostomide directly I had seen 
the animal and operculum of Mr. Guilding’s genus Megalomastoma ; 
- but from the rarity of these shells, I had little hope of so soon being 
able to get the additional information furnished by the operculum, 
which was alone wanted to clear up the doubt. I have lately seen 
another shell which has the polished surface, mouth and operculum 
of this genus, but is destitute of the groove, and must form another 
genus of this family, for which I propose the name of Callia.—J. E. 
Gray. 
ON THE BYSSUS OF UNIO. BY JOHN G. ANTHONY, ESQ.— WITH NOTES, 
BY J. E. GRAY, ESQ. 
** I have discovered another fact with regard to the Unies which 
has escaped the notice of other collectors thus far: in one locality 
“near us (Cincinnati, U. S.), the Unios spin a byssus. The location 
