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Arr. Il. Description of Two New and Remarkable Fresh 
Water Shells: Melania setosa and Unio gigas. By 
William Swainson, Esq., F.R.S., L.S., M.W.S., Se. 
[Communicated by the Autkor.] 
THE attention of several conchologists has been excited by a new 
and most extraordinary fluviatile shell, belonging to the genus 
\ 
Melania, recently brought from the Mauritius. Having been fa- 
voured with its examination, I now lay before the public the follow- 
ing description of the shell, drawn up from the only specimen 
which its discoverer, Mr. Warwick, was able to procure, after 
diligent and often repeated searches in the same locality. I take 
this opportunity also of recording the characters of another fresh- 
water shell of gigantic dimensions, equally unknown and interest- 
ing to naturalists. 
Mevania. Lam: Cuy. 
Specific character. 
M. testa ovata, ventricosa, spinis tubularibus seta bina porrecta 
‘basi connexa emittentibus coronata. Shell ovate, ventricose, co- 
Tonated by tubular spines, each sheathing the ‘base of two pro- 
truded horny bristles, 
DeEscriprion. 
Length, one inch two tenths, of which the spire occupies very © 
nearly one half. In habit the shell resembles Melania amarula, 
(Helix amarula, Lin.) but the basal volution is more ventricose, the 
spire more conic, and the tip acute; it is also much thinner, and 
may be termed subdiaphanous; the whole shell is covered by an 
olive brown epidermis; the spiral volutions are angulated, and 
marked by from three to four transverse elevated striz ; the basal 
volution is without any indication of plaits, but is slightly im- 
pressed by narrow, transverse grooves, which are wide apart; these 
are crossed by very delicate and close-set longitudinal strie; but 
whether these last are only external and belong alone to the epi- 
dermis, could not be ascertained without injury to the specimen, 
The most extraordinary characteristic of this shell, I shall now 
proceed to detail. On the upper part (or shoulder as it is some- 
times called,) of the body whorl, is a row of coronated spines, 
