142 CLASS III. GASTEROPODA. ORDER VII. PECTINIBRANCHIATA. 
NATICA, Adanson. 
Testa subglobosa, rarO ovata, spira brevi, anfractibus plus minusve 
conspicuis, ultimo umbilicum profundum, interdum impletum, for- 
mante ; columella obliqua, edentula, callo spirali interdum instructa, 
introrsus umbilicum attenuante; apertura integra, semiorbiculari, 
margine tenui, acuto. Operculum vel testaceum, vel corneum. 
The genus Natica was proposed by Adanson; and when we consider 
how materially the animals which are referred to it differ from those of 
the preceding genus, we are somewhat surprised that Linnzus did not 
more fully appreciate the labours of this intelligent traveller. The Natice 
were always included by the author of the ‘ Systema Natur’ in his genus 
Nerita; and although the twelfth edition of that work did not appear 
until some time after the publication of Adanson’s ‘ Voyage en Sénégal,’ 
they yet remained unaltered. ‘The genus Natica was, however, followed 
by Bruguiére, and it has been adopted by all succeeding naturalists, with 
the exception of Cuvier, who merely distinguished these mollusks by the 
title of ‘‘les Nérites ombiliqués.” The true organization of the Natice 
appears to have been but little known to these authors: we learn from 
M. Quoy that their shell is almost entirely concealed within the pedal disc 
asin the case of the Sigareti ; D’Orbigny gives a similar account of them ; 
and we have repeatedly confirmed this fact by our own observations. 
The Natica mamilla, and such as have a mamillary spire, with the umbili- 
cus filled up with enamel, constitute the genus Polinices of De Montford. 
The shell of Natica may be described as being somewhat globose, rarely 
ovate, and having a short spire, with the whorls more or less conspicuous, 
the last forming a deep umbilicus, which, however, is sometimes filled up ; 
the columella is oblique, edentulate, and sometimes furnished with a spiral 
callosity attenuating inwards, towards the umbilicus; the aperture is en- 
tire, and semiorbicular, with the margin thin and acute. The operculum 
is either testaceous, or horny. 
