. III. DIST. CHAR. Prototype. 101 



c- ) 77. Lignal ( lignale ) having its origin from the 



wood. 

 &c., &c. 



VALVES (valvai) the pieces of which the bivalve is composed. 



ff.)Oval (ovules} oblong, the extremities rounded and equal. 



Ovate (ovata?) oblong, the extremities rounded, but not equal. 

 In shells the extremities of the oval or ovate figure may 

 be formed either by the beak and opposite margin, or by 

 the lateral margins; according as the extent of the valves 

 from the hinge to the superior margin is greater or less, than . 

 the extent of the valves in a transverse direction. Hence 



t.) Longitudinally (fongitudinalitcr) 

 Transversly (transversim) or 



Obliquely (oblique} must be added to the terms oval, ovate,ob- 

 long, &c. when, for the sake of specific differences, it becomes 

 necessary to distinguish the direction in which the valves have 

 been produced or extended as, longitudinally oval (longi- 

 tudinaliter ovales) oval, the diameter of the valves from the 

 binge to the opposite margin exceeding the transverse, or the 

 diameter of the valves from side to side : transversly oval 

 (transversim ovales) oval in a contrary direction ; the sides 

 of the shell being equally produced and forming the two extre- 

 mities of the oval figure: obliquely oval (oblique ovales) 

 oval, but with one side of the shell more produced than the 

 other, so that the valves, though regularly oval, are inequilate- 

 ral (vahfe intequilaterce) &c., &c. 



c.)Obovate (obovata) are longitudinally ovate; but narrower at the 



base or hinge than at the opposite extremity. 

 Scrotiform (scrotiformes) are obovata ; gradually swelling from 

 a small or contracted beak and hinge, till the shell becomes 

 gibbous at the superior margin or extremity. 

 UNIVALVE (univaltii) consisting of a single piece or shell. 

 VOLUTIONS OR WREATHS (Anfractus) the circumvolutions of 

 a spiral or twisted shell. 



