Elements of conchology Prepared Elements of conchology / Prepared for the use of schools and colleges elementsofconcho00rusc Year: 1844 PARTS OF BIVALVE SHELLS. in contact with the corresponding part of th€ opposite valve, it is ' irregular,' or emarginate. Besides the parts mentioned, we shall find in most cas-es, an- terior to the apices of the beaks, a depression of variable extent and depth. This is the lunule {fig. 118, I) I it may be cordi- forna, or crescentic, lanceolate (oblong, and gradually tapering towards each extremity), oval, deep, superficial, &c. Behind the beaks is another
Elements of conchology Prepared Elements of conchology / Prepared for the use of schools and colleges elementsofconcho00rusc Year: 1844 PARTS OF BIVALVE SHELLS. in contact with the corresponding part of th€ opposite valve, it is ' irregular,' or emarginate. Besides the parts mentioned, we shall find in most cas-es, an- terior to the apices of the beaks, a depression of variable extent and depth. This is the lunule {fig. 118, I) I it may be cordi- forna, or crescentic, lanceolate (oblong, and gradually tapering towards each extremity), oval, deep, superficial, &c. Behind the beaks is another depression, longer and narrower than the lunule, and which is called the fissure (/), and its margins are named lips of the fissure (If). Behind tlie fissure there is sometimes a small depression called the suture (s). The general more or less convex surface of each valve is called the ^' venter,' or belly, which terminates in the limb^ circum- ference or margin. In the figure (118), the letters designate parts, as follows: A, anterior slope; P, posterior slope; L, left valve; R, right valve; /, lunule;/! fissure; Z/', lips of the fis- sure ; 5, suture; lig^ ligament; ny, the nymphse. • /LICANIEKT-, \ ' / NVMPHAEv \ \ Fig. 118.—CYTHEREA,
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