182 LIGUMIA. 



LEUCOSTOMA. Swainson. A genus of " Achatina," Sw. de- 

 scribed as resembling Achatinella, but having a " thick pad," at 

 tbe top of the "upper lip," and another over the base. L. 

 variegata, Sw. Lardn. Cyclop. Malac. fig. 24. 172. 



LEVENIA. G-ray, 1847. Cassis Coarctatum, &c. 



LICINA. Browne, 1756. Cistula. Humphreys, 1797. Cy- 

 CLOSTOMA fimbriata, and Thesaurus Conchyliorum. PL xxviii. 

 fig. 145, 146, and similar species having a broad fringed margin. 



LICIUM. Humph. Ottjla, Lam. (Ovulum.) 



LIGAMENT. (From Ligo, to bind.) The true ligament is 

 always external, and serves the purpose of binding the two valves 

 of a shell together externally by the posterior dorsal margins. 

 There is another substance, called by Gray the Cartilage, which 

 is elastic and of a condensed fibrous structure, placed within the 

 ligament, either close to it, or at a more" interior part of the 

 shell ; it is sometimes contained in a pit, formed for its recep- 

 tion, in the centre of the hinge. The substance, being elastic, 

 keeps the valves open, unless drawn together by the counteract- 

 ing force of the adductor muscles. When conchologists speak 

 of a shell as having the ligament external, the real meaning is 

 that these two substances are so close together as in appearance 

 to constitute one body placed outside the shell so as to be seen 

 when the valves are closed. When two ligaments are spoken 

 of, as in Amphidesma, the meaning is that the cartilage occupies 

 a separate place on the hinge. 



LIGAMENTIEEEOUS. (Ligamentum, a ligament, /ero, to bear.) 

 Having or containing the ligament, as the cardinal pit in Mya, 

 fig. 71. 



LIGrULA. Leach. A genus containing the more rounded and less 

 gaping species of Lutrabia, Auct. Eig. 77, Lutraria Papyracea. 



LIG-TJLATE. {Ligula, a slip, a shoe-latchet.) Thin, slender, like 

 a slip, or neck of any thing, as the anterior muscular impression 

 of Lucina, fig. 104. 



LIGrUMIA. Swainson. A sub-genus of Unio, thus described : — 

 " Very long and pod-shaped ; bosses depressed ; cardinal teeth 

 moderate. S. recta, Lam. vi. 1. p. 74." Sw. p. 378. 



