286 LIMID^. 



smooth, aud ornamented posteriorly, as also the free portion of 

 the right valve, bj^ concentric plications or radiating ribs. 

 Hinge-area triangular, transverse, striated in the same direction, 

 edentulous, sometimes produced in the middle line ; ligaraental 

 furrow median, longitudinal, straight, rather narrow. Muscular 

 scar near the posterior margin ; pallial line wanting. Externally 

 the shells of this genus resemble those of Hinnites and Ostrea. 



Family LIMID^. 



Shell eared, white, gaping at the sides ; hinge edentulous, with 

 a central, triangular cartilage-pit. 



The large development of the internal thin layer of the mantle, 

 forming an open bag, appears to be destined for hatching the 

 eggs, and is no doubt also an important organ for retaining 

 water while swimming. 



Mostly extinct, from palaeozoic. Nearly 300 fossil species, 

 but few of them in the new world. 



Lima, Bruguifere, IT 92. 



Etym. — Lima, a file. Syn. — Radula, Klein. 



Distr. — 20 sp. Norway, Britain, W. Indies, Canaries, India, 

 Australia; 1-150 fms. The largest living species (L. excavata, 

 Chemn.) is found on the coast of Norway. Fossil, 300 sp. Carb., 

 Trias — ; United States, Europe, India. L. squamosa, Lam. 

 (cxxxii, 91, 92^. 



, Shell equivalve, compressed, obliquely oval ; anterior side 

 straight, gaping, posterior rounded, usually close ; umbones 

 apart, eared ; valves white, smooth, punctate-striate, or radiately 

 ribbed and imbricated ; there is usually a thin, brownish 

 epidermis; hinge-area triangular, cartilage-pit central; adductor 

 impression lateral, large, double ; pedal scars two, small. 



Animal : mantle-margins separate, inner pendent, fringed with 

 long tentacular filaments, ocelli inconspicuous ; foot finger-like, 

 grooved ; lips with tentacular filaments, palpi small, striated 

 inside ; gills equal on each side, distinct. 



The shell is always white ; its outer laj^er consists of coarsely 

 plicated membranous lamellae ; the inner layer is perforated by 

 minute tubuli, forming a complete network. — Carpenter. 



" The Lima moves or rather darts through the water like a 

 scallop, but in a contrary posture. The hinder instead of the 

 ventral end is in front, so that the mode of its progression may 

 be compared to that of a fish swimming tail foremost. Some 

 species construct dwelling-places called ' nests ' out of frag- 

 ments of shell, nuUipores, gravel and other material, which they 

 ingeniously fasten together b}^ their byssal threads and attach 

 to the roots of large sea-weeds. Several young ones often occupy 



