PURPURA. 89 
penus, containing the shells commonly called Devils-claws, 
Gouty Scorpions, Spiders, &c. is distinguished from Strombus by 
the digitations of the outer lip. No fossil species are known. 
Fig. 405, P. aurantiaca. 
PTERO’PODA, Lam. (mrepov, pteron, a wing; mus, pus, a foot.) 
The first order of the class Mollusca, Lam. consisting of molluscs 
whose organs of locomotion consist of a pair of wing-shaped 
fins. This order contains the genera Hyalza, Clio, Cleodora, 
Limacella, Cymbulia, and Pneumoderma. To which may be 
added other genera enumerated in explanation of fig. 220 to 
226. 
PTERO’PODA. Bl. Second family of Nucleobranchiata. BI. 
containing the genera, Atlanta, Spiratella and Argonauta. 
PULLAS'TRA. Sow. Fam. Conques Marines, Lam. Descr. 
Equivalve, ovate or oblong, transverse, inequilateral; hinge 
with three diverging, cardinal teeth in each valve, notched at the 
terminations; muscular impressions two in each valve; palleal 
impression having a large sinus; ligament external, partly hidden 
by the dorsal margin. Obs. This genus includes the Veneri- 
rupes of Lamarck, and several species of his Veneres. Fig. 
120. P. textile. 
PULMONOBRANCHIA'TA. Bl. The first order of the first 
section of Paracephalophora monoica, containing the families 
Limnacea, Auriculacea, Limacinea. 
PULVINI'TES, Defr. (Pulvinus,acushion.) Fam. Malleacea, 
Lam. Descr. Sub-equivalve, inequilateral, compressed, thin, 
slightly gaping posteriorly; one valve flat, the other rather con- - 
cave ; hinge linear, short, divided into perpendicular grooves; 
muscular impressions two, one sub-central, the other above it 
nearer the hinge. Obs. This fossil shell is imperfectly known, 
and it is difficult to give a sufficient reason for separating it from 
Perna. It comes from the Baculite Limestone of Normandy. 
Fig. 170, P. Adansonii. 
PUNCTUREL‘LA. Lowe. Cemoria, Leach. 
PU’PA. Auct. Fam. Colimacea, Lam. Limacinea, Bl. Deser. 
Cylindrical, generally ribbed; spire long, obtuse, composed of 
numerous, slowly increasing whorls; aperture sub-quadrate, 
rounded anteriorly, entire; outer-lip thickened, columella 
plaited. Obs. This genus is composed of land shells very varia- 
ble in form. differing from Bulinus in the numerous, slowly 
increasing whorls of the spire, and in the plice on the columella; 
and from Clausilia in the want of a clausium. P. Uva, fig. 291. 
PUR’PURA. Auct. (The shell-fish from which purple is taken, 
Plin.) Fam. Purpurifera, Lam. Entomostomata. Bl. Deser. 
Oval or oblong, thick; spire for the most part short, sometimes 
rather longer; external surface generally sulcated, granulated, 
tuberculated or muricated; aperture large, oval, somewhat dila- 
N 
