FAMILY 8. CANALIFERA. Avi 
CERITHIUM, Bruguiére. 
Testa turriculata, extus plerumque rugosa; anfractibus plurimis, spira 
regulari, apice subacuto, interdum eroso, seu decollato ; apertura 
semirotunda, vel oblonga ; columella arcuata, plica subspirali, se- 
pils reflexa, canalis marginem superiorem formante ; labro plerum- 
que incrassato, nonnunquam late reflexo. 
We have now to describe a group of mollusks, that were assembled un- 
der the above title by Bruguiére for the first time in the ‘ Encyclopédie 
Méthodique ;’ the word Cerithium had however been previously used in 
reference to some few of the species both by Adanson and Fabius Columna. 
They were distributed by Linnzeus in the genera Murex, Strombus, and Tro- 
chus, but are nevertheless well characterized by the turriculated structure 
of their shells, which are always more or less strongly canaliculated at the 
base of the aperture. The Cerithia may be considered as intermediate, 
both in their habits and external characters, between the fusiform marine, 
and the fusiform freshwater kinds of this class; so much so, that many 
authors have been tempted to arrange them on this account in the same 
natural division-with the Melanie. The fact is, that as many of the Ce- 
rithia are found located at the mouths of estuaries. at the confluence of 
rivers with the sea, and in other places where the water is brackish, their 
habits as well as the composition of their shells become modified in a man- 
ner similar to those of the freshwater mollusks, and they assume almost 
the same sombre appearance. Brongniart, considering this variation of 
some geological importance, proposed to separate the semi-fluviatile Ce- 
rithia from those that are strictly marine, under the new title of Potamis: 
in studying them, however, in the living state, we can attach no import- 
ance to that which, arising from only a slight modification of circumstance, 
produces no change in their structure or organization. 
The shell of Cerithium may be described as being turriculated, gene- 
rally rough on the outside, and composed of numerous whorls, forming 
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