2 GENUS PYRAMIDELLA. 
Quoy and Gaimard, to whom we are indebted for a knowledge 
of these animals, suppose that they have the sexes united in an 
incomplete hermaphroditism ; these writers have not been able, 
satisfactorily, to examine the organs of generation. 
The general color of the body of these mollusca, is of a dull 
white. The operculum only, and the edge of the mantle are 
yellowish. 
Lamarck, in his Histoire des Animaux sans vertébres (1801), 
first formed the genus PyramipEeLia from the Trocuus dola- 
bratus of Linneus, and the Butimus terebellum of Brugui€re ; 
he placed it between Mexanra and Auricuta, considering the 
species which composed it, as fresh water shells. Some years 
after he suppressed this genus, and again re-established it in 
the compendium of his course in 1811; but during the inter- 
val elapsing between these two periods, De Roissy and Montfort 
had retained and admitted it, one in Sonnini’s Buffon, the other 
in his Conchyliologie Systématique ; and when, in 1811,. La- 
marck, after a more mature examination, coincided with them, 
or rather acknowledged the justness of his first opinion, he 
approximated the genus ‘TornaTELLA to the PyramipE.a, and 
thence formed a family under the name of PLICACEA; the 
- analogies which he found between these two genera, by blending 
them, induced him to place them near to the MACROSTOME 
and the SCALAR ; this little family has appeared established 
so naturally, that it has remained almost unmodified, in the 
principal systems published since that time. 
Cuvier, in the first edition of his Régne Animal, placed the 
shells of this genus in the family of the 4URICUL; this decision 
was followed by Férussac, in his Tableau systématique ; but in 
the second edition of the Regne Animal, its illustrious author 
‘concurs with the opinion of Lamarck, in bringing these two 
genera into the family PECTINIBRANCHIATA, among the 
MELANIE and the JANTHINE. 
Blainville, Traité de Malacologie, p. 453, arranges them 
among his AURICUL, and has not adopted the division PLI 
CACEA of Lamarck; but, afterwards, becoming acquainted with 
the operculum of the animal of the Tornavrexya, this writer 
judged that it ought no longer to hold the place which he had at 
first assigned it, without, however, pointing out another. In fact, 
