90 PYRGOMA. 
ted, emarginated anteriorly; outer-lip crenated, acute: colu- 
mella flattened; operculum horny with the nucleus lateral, thin 
towards the columella. Obs. True Purpure are to be found in 
the Lamarckian genera Buccinum, Ricinula, and others. They 
may be generally distinguished by the flatness of the columellar 
lip, and by the short canal or emargination, which is not reflected, 
and raised as in Buccinum. The species are very numerous and 
very variable in form, inhabiting the seas of temperate and trop- 
ical climates. The animals secrete a purple liquor which has 
formerly been used advantageously for dying. Fig. 414, P. 
ersica. 
PURPURIFERA. Lam. (Purpura, purple; fero, to carry.) A 
family belonging to the second section of Lamarck’s order 
Trachelipoda, containing the genera Cassidaria, Cassis, Ricinula, 
Purpura, Monoceros, Concholepas, Harpa, Dolhium, Buccinum, 
Eburna, Terebra. To which may be added other genera enu- 
merated in explanation of fig. 407 to 429. 
PYLORI’DEA. Bl. The ninth family of the order Lammelli- 
branchiata, Bl. divided into: Section 1. Genera of bivalves with 
internal ligaments, Pandora, Thracia, Anatina, Mya, Lutricola. 
Section 2. Ligament external, Psammocola, Soletellina, Solen, 
Sanguinolaria, Solenocurtus, Solenimya, Panopzea, Glycimeris, 
Saxicava, Byssomya, Rhomboides, Hiatella, Gastrochzena, Cla- 
vagella, Aspergillum. 
PYRAMIDEL'LA. Lam. (A little pyramid.) Fam. Plicacea, 
Lam. Auriculacea, Bl. Descr. Pyramidal, smooth, polished ; 
spire long, pointed, composed of numerous whorls; aperture 
. small, modified by the last whorl, rounded anteriorly; outer-lip 
somewhat expanded; columella tortuous, with several folds. 
Obs. This is a genus of pretty little marine shells. Fig. 342. 
PYRA’ZUS. Montf. Poramis, Brogniart. 
PYREL'LA, Sw. (A little pear.) A genus consisting of Tur- 
binellus Spirilla, Auct. and other similar species, having a long 
channel, a pyriform outline, and one strong plait at the base of 
the columella, the apex of the spire enlarged. P. spirillus, fig. 
384. The proper term would be Spirilla. 
PYRI’FORM. (Pyrum,a pear; forma, shape.) Shaped like a pear, 
i. e. large and rounding at one end, and gradually tapering at 
the other. Ew. Pyrula, fig. 390. 
PYR’GO. Defr. A genus of microscopic Foraminifera. 
PYR’GOMA. Auct. (Hupyos, pyrgus, a tower.) Order. Sessile 
Cirripedes, Lam. Descr. Composed of a single conical, hollow 
paries with a small aperture enclosed by an operculum of four 
valves, and supported upon a cup-shaped base. Obs. The genera 
into which Leach has divided this genus are Pyrgoma, Adna, 
and Megatrema;. his genera Nobiaand Savignium differ in hav- 
- ing but two valves to the operculum. Pyrgoma differs from 
