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L I A 



unacquainted with any existing species of 

 plant, which, like the lepidodendron, pre- 

 serves at all ages, and throughout the 

 whole extent of the trunk, the scars 

 formed by the attachment of the petioles, 

 or leaf-stalks, or the markings of the ad- 

 hesion of the leaves themselves. 



LE'PIDOIDS. A family of extinct fossil 

 fishes, found in the oolitic series : they 

 were remarkable for their large rhomboidal 

 bony scales, which were of great thick- 

 ness, and covered with enamel. The 

 scales of lepidoids had a remarkable struc- 

 ture in being furnished on their upper 

 margin with a hook-like process, placed 

 like the hook or peg near the upper mar- 

 gin of a roofing tile ; this hook fitted into 

 a depression on the lower margin of the 

 scale placed immediately above it. In 

 order to obtain a correct notion of the 

 form and appearance of the scales, the 

 reader is referred to Prof. Buckland's 

 Bridgewater Treatise, in which they are 

 very accurately figured. 



LEPI'DOLITE. (from XETTIC, a scale, and 

 Xi'0oc, a stone, Gr.) The Lepidolith of 

 Werner ; Hemiprismatischer Talk-glim- 

 mer of Mohs. Lepidolite Mica. A mi- 

 neral of a peach-blossom, red, and some- 

 times grey colour, occurring massive and 

 in small concretions. This mineral, at 

 first view, appears to be composed of 

 small grains, sometimes extremely minute ; 

 but these grains, among which little pearly 

 scales are often interspersed, are them- 

 selves composed of a great number of mi- 

 nute foliae or spangles, like those of mica, 

 from which circumstance it has obtained 

 its name. Its constituents have been 

 variously stated. According to some au- 

 thors, it contains silica 50'36, alumina 

 28'32, potash 9'0, oxide of manganese 

 1*25, fluoric acid and water 5'40, lithion 

 5'50. It exhibits two axes of double re- 

 fraction, from which circumstance it has 

 been called Di-axial mica. From the 

 beauty of its colour it has been cut into 

 snuff- boxes. 



LEPIDO'PTERA. (from XCTTIC, a scale, and 

 n-Tfpbv, a wing, Gr.) Scaly-winged in- 

 sects. Lepidoptera form the tenth order 

 of insects in Cuvier's arrangement ; they 

 have four wings, both sides of which are 

 covered with small, coloured scales, re- 

 sembling farinaceous dust. This order 

 comprises butterflies, moths, and sphinxes. 

 The scales are attached so slightly to the 

 membrane of the wing as to come off 

 when touched with the fingers, to which 

 they adhere like fine dust. When ex- 

 amined with the microscope, their con- 

 struction and arrangement appear to be 

 exceedingly beautiful, being marked with 

 parallel and equidistant strive, often 

 crossed by still finer lines. The former 



of these scales are exceedingly diversified, 

 not only in different species, but also in 

 different parts of the same insect. The 

 proboscis of the Lepidoptera is a double 

 tube. 



LEPIDO'PTERAL. ) Belonging to the order 



LEPIDO'PTEROUS. { Lepidoptera ; having 

 wings covered with scales. The progress 

 of the metamorphoses of insects is most 

 strikingly displayed in the history of the 

 Lepidopterous, or butterfly and moth 

 tribe. 



LEPIDO'STEUS. ) (The Lepisosteus of La- 



LEPISO'STEUS. $ cepede. ) A genus of 

 fishes inhabiting the rivers of North Ame- 

 rica, one of the two living representative 

 genera of Sauroid fishes. Teeth of a fish 

 related to Lepidosteus, or Lepisosteus, 

 have been found in the Tilgate beds and 

 in those of Stonesfield. 



LEPISO'STEUS FITTONI. A species of fossil 

 Lepisosteus, thus named after Dr. Fit- 

 ton. Scales with bifurcating processes, 

 belonging to the Lepisosteus Fittoni, are 

 very abundantly found in the Tilgate 

 strata. 



LEPIDO'TUS. An extinct genus of fishes 

 belonging to the oolite series. 



LEU'CIN. > (from XeiKoc, white, Gr.) The 



LEU'CINE. \ name given by M. Bracounot 

 to a white substance obtained from mus- 

 cular fibre, by treating it with sulphuric 

 acid, and subjecting it to a peculiar pro- 

 cess. 



LEU'CITE. (from Xev/coc, Gr.) A mineral 

 of a white colour, found in volcanic rocks. 

 The Leuzit of Werner ; Amphigene of 

 Haiiy ; Vesuvian of Kirwan ; Trapezoi- 

 daler Kuphon-spath of Mohs. Before 

 the blow-pipe it is infusible, a circum- 

 stance which serves to distinguish leucite 

 from the garnet and analcime. Its consti- 

 tuents are silex 53'75, alumine 24 - 62, 

 potash 21 '35. It occurs regularly crys- 

 tallized ; in granular concretions, and in 

 roundish grains. It is often embedded 

 in lava and in basalt. All lavas do not 

 contain crystals of leucite. In the lava 

 of Vesuvius they are abundant, but in 

 that of Etna they are rarely found. Some 

 authors have supposed that the crystals 

 of leucite found in lava pre-existed in the 

 mineral fused by volcanic heat, but that 

 in consequence of their infusibility these 

 crystals were not acted on ; others main- 

 tain that the Leucite has crystallized 

 within the lava. 



LEUCI'TIC. Containing leucite ; resem- 

 bling leucite. 



LEU'TTRITE. A mineral found in Leuttra, 

 in Saxony, and thus named from that 

 circumstance. Colour, grayish-white, 

 tinged in places with an ochreous brown . 



LI'AS. A provincial name, now become 

 conventional amongst geologists, for a 



