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able in a fresh water genus. Mr. Smith, from the similarity 
of the operculum, which is horny and few whorled, places 
the genus amongst the Littorinidse and near the genus 
Echinella and Risella, which it resembles in configuration , 
It is, of course, impossible to ascertain actually the position 
of the genus until the animal has been examined, but 
judging from the shell alone, Mr. Melvill considered it 
more approached the genus Solarium — § Philippia, agreeing 
with that in the ornamented edge of the whorls, and in 
the deep umbilicus, which latter is wanting throughout the 
whole of the Littorinidse; with the exception of the genus 
Echinella. The operculum of Limnotrochus is certainly 
Littorinoid. 
He also exhibited a shell of even greater interest, recently 
discovered by Prof. Morelet, as a new genus, Cyclosurus, 
from the Mayotte or Mayotta Islands, about 300 miles 
N.W. of Madagascar, at the northern entrance to the 
Mozambique Channel. 
This land mollusc Cyclosurus, Mariei, (Morelet) was 
recently discovered there, but few specimens have hitherto 
found their way to Europe, and, although closely allied to 
the genus Cyclophorus, the shell bears more resemblance to 
a Dentalium, being altogether e volute with the exception 
of the first two very small whorls, after which it projects 
straight like a horn. 
It is also conspicuous for being very minutely ribbed 
longitudinally, each rib bearing a quantity of very minute 
rough spines. 
It was suggested by Mr. Rogers that it might be a mons- 
trosity, but this can hardly be the case, as if a monstrosity, 
it is that of an undescribed species, the texture being dis- 
similar from any known shell, and, besides; all the specimens 
that have been discovered are of a similar evolute formation. 
