LOW 



[267] 



L TJ D 



ches inferieures, of the French. 

 The lowest subdivision of the New 

 Bed System. For a description 

 see Rothe-todte-liegende. It being 

 now fully proved by Sir R. Mur- 

 chison that the lower new red 

 sandstone graduates into the coal- 

 measures, a practical acquaintance 

 with this division of the new red 

 system becomes a matter of great 

 national importance. The maxi- 

 mum thickness of the lower new 

 red sandstone hitherto observed is 

 1000 feet; this formation is inter- 

 polated between the magnesian 

 limestone and the coal-measures. 



LOWER OLD RED SANDSTONE. This 

 formation found in Scotland is the 

 representative of the Tilestone of 

 the Old lied System of England, 

 but in extent of vertical develop- 

 ment it far exceeds it. The tile- 

 stones compose the least of the 

 three divisions in England; their 

 representative in Scotland forms 

 by much the greatest of the three. 

 Hugh Miller. 



LOWER LUDLOW ROCK. The name 

 given to the third or lowest sub- 

 division of the Ludlow formation. 

 The strata of the lower differ from 

 those of the upper Ludlow rock in 

 being more argillaceous, less sandy 

 and calcareous, with rarely a trace 

 of mica. They constitute, in fact, 

 says Sir R. Murchison, a great 

 argillaceous mass strictly entitled 

 to the provincial name of mudstone. 

 The organic remains of the lower 

 Ludlow rock are upon the whole 

 very different from those of the 

 upper, as well as the Aymestry 

 limestone : for although some spe- 

 cies of shell are common to the 

 whole formation, the lower Ludlow 

 rock is characterized by many pe- 

 culiar remains, including two new 

 genera which have not been ob- 

 served in any overlying stratum; 

 namely, the conchifer Cardiola, and 

 the chambered shell Phragmoceras. 

 These, with the Orthoceras filosum 



and Orthoceras pyriforme ; the Li- 

 tuites giganteus, and the Grapto- 

 lites Ludensis, are peculiar and 

 distinguishing fossils. 



LO'ZENGED. In entomology, of a 

 quadrangular shape, with two op- 

 posite angles acute, and two obtuse. 



LTTCERNAHO'IDA. The first order of 

 the class Hydrozoa, comprising 

 sertularia, and similar zoophytes. 



LTTCI'NA. A genus of equivalve bivalve 

 shells belonging to the Nymphacea 

 of Lamark. They are orbicular, 

 flattened, andradiately striated; the 

 hinge has usually two small cardi- 

 nal teeth, and two lateral teeth on 

 each side of the umbo in one valve, 

 and one in the other; the ligament 

 is external, which distinguishes it 

 from Amphidesma. The species 

 are numerous, both living and 

 fossil, more especially the latter. 



LTTCTT'LLITE. (from Lucius Lucullus, 

 a celebrated Roman, who is said 

 greatly to have admired it.) A 

 black variety of transition lime- 

 stone, a black marble. 



LTJDLOW FORMATION. ) The term has 



LUDLOW ROCKS. j been selected 



because the town of Ludlow is built 

 upon the upper beds. The Ludlow 

 rocks form one of the four divisions 

 of the Silurian system, and have 

 been sub-divided into the Upper 

 Ludlow rocks, the Aymestry lime- 

 stone, and the Lower Ludlow rocks. 

 They consist of beds of sandstone, 

 shale and limestone. The upper 

 Ludlow rocks of slightly micaceous, 

 gray-coloured, thin-bedded sand- 

 stone: the Aymestry limestone of 

 sub-crystalline grey or blue argil- 

 laceous limestone ; the lower Lud- 

 low rocks of sandy, liver and dark 

 coloured shale and flag, with con- 

 cretions of earthy limestone. These 

 rocks are developed principally in 

 Shropshire, Herefordshire, Wor- 

 cestershire, Staffordshire, and Glou- 

 cestershire, in England, and in Rad- 

 norshire, Brecknockshire, Montgo- 

 meryshire, Glamorganshire, and 



