LEPTON. 17 
branchial siphon; but there are mantellar folds, which, with 
the great ventral opening, amply provide for the admission of 
the water. 
The animals of this interesting group exhibit, in the tenta- 
cular filaments and curious foot, as well as in the sculpture of 
their shells, very considerable variation from Kellia rubra and 
Kellia suborbicularis,—the types of one of the genera of the 
family in which they have been located by authors, doubtless 
from the want of knowledge of the animal. Taking into 
consideration that the Leptons have many of the attributes 
of the Arcade, and especially givng due weight to the re- 
v.arkable similarity between the foot of Lepton squamosum 
and the Pectunculus pilosus, | am almost induced to believe 
that it is in a false position, m connexion with the Kedliade, 
and that it ought to follow or precede Galeomma, which, with 
me, is an undoubted genus of the Arcade. 
The punctures of this species and of L. convexwin are in the 
test; with respect to its congener, the L. nitidum, it has 
been stated that it is smooth and without punctures: this is 
a mistake, as I can show fifty specimens not only well- 
marked on the greenish epidermis, but in the substance of 
the shell. 
I have the satisfaction to state, that I have observed another 
live L. sguamosum, and also obtained full notes of the animal 
of one of our great desiderata, the L. nitidum, from a most 
lively animal, which for several days gave me every facility 
for examination. The L. sguamosum, just alluded to, was 
kept thirty-four days m a glass of sea-water, changed daily, 
and was apparently as vigorous as when first placed in captivity ; 
it thus appears that the Conchifera can exist for a long time 
in pure sea-water, on the animalculz it contains, though that 
aliment may not be their sole resource in freedom. 
I may observe, that the habitude of crawling and swimming 
with the foot uppermost in Lepton, and in several other minute 
bivalves, perhaps in all, shows the close alliance of the Acephala 
with the Gasteropoda, all of which, m their mimute condition, 
have precisely the same peculiar system of dorsal natation. I 
ought to have mentioned that the liver is light green and 
