232 PLICATULA. 



PLEUROTOMARIA. Defr. Fam. Turbinacea, Lam.— Descr. 

 Turbinated, spiral ; aperture sub- quadrate, with rounded angles ; 

 outer lip with a deep slit near its union with the spire. — Obs. 

 This genus, which is only known in a fossil state, abounds in in- 

 ferior Oolite, Oxford clay, and casts are found in a limestone 

 bed in Norway. The Scissurellae differ in being very minute 

 shells, and are not so trochiform as the species of Pleurotomaria, 

 P. reticulata, fig. 34 1 . 



PLICACEA. Lam. A family of the order Trachelipoda, Lam. 

 containing the following genera : 



1. Pyramidella. Pyramidal, with numerous whorls. Fig. 



342. 



2. Tornatella. Cylindrical, with few whorls. Fig. 343, 



344. 



3. Ringicula. Margin reflected. Fig. 540, 541. 

 PLICADOMUS. Sw. A sub-genus of Pupa, thus described : 



u spire moderate, regular and thick, but gradually conic; the 

 tip obtuse ; aperture perpendicular ; inner lip wanting ; outer 

 lip semicircular ; the margin dilated and reflected. P. sulcata, 

 Chem. 135, f. 1231, 1232." Sw. p. 332. 



PLICATED. {Plicatus, folded.) Applied to spiral plaits on the 

 columella of some shells. Ex. Voluta, fig. 433. Also to the 

 angular bendings in the margins of some bivalve shells. Ex. 

 Dendostrea, fig. 181. 



PLICATULA. Lam. (Plicatus, folded.) Fam. Pectenides, Lam. 

 Sub-ostracea, Bl. — Descr. Irregular, sub -e qui valve, sub-equi- 

 lateral, attached by a small part of the surface of one valve, 

 strongly plicated ; umbones separated by a small, external liga- 

 mentary area ; hinge with two cardinal teeth in each valve, two 

 approximate in one valve, received between two distant in the 

 other ; cartilage placed between the cardinal teeth ; muscular 

 impressions one in each valve. — Obs. The cardinal teeth resem- 

 bling those of Spondylus, distinguish this genus from others of 

 the Lamarckian family Pectenides. Very few species are yet 

 known, they are brought from the East and West Indies and the 



