FAMILY 6. TURBINACEA. 151 
this last family he introduces certain genera, such as Siliquaria, Cyclo- 
stoma, Paludina, &c., of the most anomalous character, for reasons which 
we cannot understand. 
The shell of the Turbinacea may be described as being either conoidal, 
or turriculated, with the whorls sometimes closely, sometimes loosely 
coiled together, and it is generally furnished with an operculum, which 
is either horny or shelly in species of the same genus. 
The following are the thirteen genera which we refer to this family : 
Rissoa. Trocuvus. 
Eu.Lima. TuRBo. 
ScALARIA. MarGarITa. 
DELPHINULA. Lirrorina. 
SoLarium. PHASIANELLA. 
Puorus. TURRITELLA. 
RoreLia. 
RISSOA, Fréminville. 
Testa parva, turriculata, apice acuminato ; apertura ovali, suborbiculari, 
integra, superné trigoniuscula, inferné subeffusa, margine incrassato, 
non reflexo, prope ad columellam, subcanaliculato. Operculum cor- 
neum. 
The genus Rissoa was proposed by Fréminville for the reception of a 
few mollusks that had been confounded by Lamarck with the Turbines 
and the Melanie ; they were also distinguished about the same time by 
Hartmann, in his account of the shells of Switzerland, by the generic title 
of Acmea. Linnzus appears also to have referred the only species with 
which he was acquainted to his genus Turbo, probably on account of a 
certain resemblance in its shell to that of Scalaria ; it differs, however, in 
