180 MACRODITUS. 



lip crossed by several irregular ridges, without any distinct mar- 

 ginal ones, internally narrow, flat ; the shell pear-shaped, 

 smooth, or cross-ribbed. Ex. C. Algoensis, Luponia Algoensis, 

 Gray, fig. 447. 



LUTRARIA. Auct. (Lutum? mud.) — Fam. Mactracea, Lam. — 

 Descr. Thin, equivalve, inequilateral, transverse, oblong or ovate, 

 gaping at both extremities ; hinge with one double and some- 

 times one single cardinal tooth in each valve, and a triangular, 

 oblique pit with a prominent margin, containing the ligament; 

 muscular impressions distant ; palleal impression having a large 

 sinus. — Obs. This genus differs from Mactra in the entire absence 

 or indistinctness of lateral teeth. Fig. 77, L. Papyracea. (Ligula, 

 Leach.) Fig. 78. L. Solenoides. Sandy and muddy shores. 



LUTPJCOLA. Bl. Lutraria. Lam. Fig. 77, 78. 



LYCOPHRIS. Montf. A microscopic fossil described as resem- 

 bling Nummulites, but having a granulated surface. 



LYMNADEA. Sw. A sub-genus of " Mysca," Turton, in the 

 family of Nayades, Lam. thus described : " Posterior hinge margin 

 elevated and winged ; the valves connate ; the surface smooth. 

 L. alata Sw. Ex. Conch, (fig. 48.) fragilis. Sw. Zool. 111. com- 

 pressa, Lea. Am. Tr. iii. pi. 12. f. 22." Sw. p. 379. 



LYMNEA. See Limnea. 



LYMNEUS. Lam. See Limneana. 



LYONSIA. Turt. Inequivalve species of Anatina, Auct. which 

 have no spoon-shaped cavity in the hinge, but an accessary piece. 

 L. striata, fig. 491, 2. 



LYRODON. Goldf. Trigonia? 



MACLURITES. Lesuour. Journ. des Scienc. Nat. Philad. t. 1. 

 p. 312. pi. 13. fig. 2, 3. 



MACOMA. Leach. Venus tenuis, Bl. and similar species, de- 

 scribed as " Clothed with an epidermis; striated, compressed, 

 oval; the summits not very prominent; two bifid teeth upon 

 the right valve and a single undivided one upon the left." 



MACRODITUS. Montf. Lenticulina, Bl. A genus of micros- 

 copic Foraminifera. 



