246 CLASS III. GASTEROPODA. ORDER VII. PECTINIBRANCHIATA. 
The family of the Columellata includes a small but rich series of mol- 
lusks, distinguished in great measure by the decided manner in which 
their shells are plaited on the columella. We say in great measure, 
because there are other mollusks differing most essentially both in their 
organization and habits, such as the Auriculacea, for example, whose 
shells exhibit the same important feature on the pillar-lip. But the Co- 
lumellata will be found to agree in many other prominent peculiarities, 
and De Blainville includes them, together with the Convoluta, in one and 
the same family, Angyostomata ; we think, however, the method adopted 
by Lamarck, of regarding them as separate groups, may be profitably fol- 
lowed. One genus, Columbella, was referred to this division by Lamarck, 
but we have shown it to have been misplaced ; it was founded upon an 
erroneous association of character, and is one of the very few misappro- 
priations of that great master of conchological science. 
The shells of this group may be described as being emarginated at the 
base, for the passage of a stout proboscis, and strongly plaited on the 
columella, the lowest of these plaits being sometimes the largest, some- 
times the smallest. 
The family of the Columellata includes the six following genera : 
VoLvaARia. VoLuta. 
MarGINELLA. ME Lo. 
Mirra. CyMBA. 
VOLV ARIA, Lamarck. 
Testa longiuscula, subquadrato-cylindrica, ad basem leviter sinuata, ex- 
tis transversim striata, spira depressa, pené occulta; apertura per- 
angusta, teste longitudinem equante; columella recta, prope ad 
basem obliqué plicata, labro paululum denticulato. 
The genus Volvaria was introduced by Lamarck in an early publication, 
