PANDORA. 229 



P^LLIOBEANCHIATA. Bl. The first order of the class 

 Acephalophora. Bl. The animals of this order are described 

 as more or less compressed, included between the two valves 

 of a bivalve shell, one inferior, the other superior, joining at the 

 back and opening in front. The Palliobranchiata in the system 

 of De Blainville correspond with the Brachiopoda in the system 

 of Lamarck, and the shells may be known by their being sym- 

 metrical. This order contains in the first section of symmetrical 

 bivalves, Lingula, Terebratula, Thecidium, Strophomena, Plagio- 

 stoma, Dianchora and Podopsis ; in the second section, Orbicula 

 and Crania. 



PALMATED. Flattened like a palm, as the fronds or fringes 

 of some Murices. 



PALMINA. Gray. Difiering from Otion in having but one 

 auricle. 



PALUDINA. Lam. Vam. Peristomata, Lam. Cricostomata, 

 Bl. — Descr. Varying in form from oval to globose, in some 

 instances oblong, covered with a greenish horny epidermis ; spire 

 acute, composed of rounded whorls ; aperture ovate ; peritreme 

 entire, slightly modified by the last whorl ; operculum horny, 

 concentric. Europe, North America, East Indies, China, &c. — 

 Ohs. The construction of the operculum distinguishes this genus 

 of fresh-water shells from Yalvata and Cyclostoma. The Palu- 

 dinse are viviparous. P. Achatina, PI. xv. fig. 321. 



PALUDOMUS. Swainson. A genus of the family of " Melani- 

 an«," Sw. described as differing from Melania in having the 

 spire shorter than the aperture. Sw. p. 340. Mr. Eeeve's 

 Monograph, contains 15 species. See our Plate xxviii. fig. 583. 



PANDOEA. Brug. Fam. Corbulacea, Lam. Pyloridea, Bl.-^ 

 T)escr. Thin, inequivalve, pearly within, rounded anteriorly, 

 rostrated posteriorly ; right valve flat witli a cardinal tooth, or 

 stort rib, and a slit containing the cartilage with a narrow plate 

 on the dorsal edge turned towards the left valve; left valve 

 concave, with a receptacle for the cardinal tooth of the right 

 valve and the internal cartilage ; no external ligament. Europe, 

 America, Ceylon, &c.--Obs. This well known genus is in no 



