GLOSSARY. 205 



Muscular Impressiovs, are the marks made by the muscles 

 with which the animal adheres to the shell, as in the Com- 

 mon Oyster. 



Obovate, nearly oval. 



Obsolete, obliterated. 



Obtuse, blunt pointed. 



Operculum, (in Multivalves), the stellular valves which shut 

 up the superior oriBce: (in Univalves), the part which ex- 

 actly fits into the aperture and encloses the animal. 



Orbicular, forming an entire circle. 



Pa/;j7/«»-y, having the apex rounded. 



Papyraceous, of the thinness of paper. 



Patulous, gaping. 



Pectinated, when the longitudinal ribs on the anterior surface 



form acute angles with the transverse striae. 

 Peduncle, a tendinous substance belonging to some of the 



Multivalves, by means of which they adhere to solid bodies. 

 Pillar, see Columella. 

 Pillar-lip, that side of the aperture in which the columella is 



situated. 

 Pisiform, pea-like. 



Plaited, when the columella is toothed, as in Volutes. 

 Posterior, see Margin. 



Reticulated, like net-work. 



Retuse, when the lower whorls are pressed into the body. 



Rostrum, see Beak. 



Rugose, wrinkled. 



Scabrous, rough. 



Serrated, toothed like a saw. 



Semilunar, like a half-moon. 



