Joints. Fissures or lines of parting in rocks, often at right angles to the planes of stratification. The partings which divide columnar basalt into prisms are joints.
Jura Limestone. The limestones belonging to the Oolite Group constitute the chief part of the mountains of Jura between France and Switzerland; and hence the geologists of the Continent have given the name to the group.
Keuper. A German name for a member of the Upper New Red Sandstone.
Kimmeridge Clay. A thick bed of clay, constituting a member of the Oolite Group. So called because it is found well developed at Kimmeridge, in the Isle of Purbeck, Dorsetshire.
Lacustrine. Belonging to a lake. Etym., lacus, a lake.
Lamantine. A living species of the herbivorous Cetacea or whale tribe which inhabits the mouth of rivers on the coasts of Africa and South America: the sea-cow.
Lamelliferous. Having a structure consisting of thin plates or leaves like paper. Etym., lamella, the diminutive of lamina, plate, and fero, to bear.
Laminæ. Latin for plates; used in geology for the smaller layers of which a stratum is frequently composed.
Landslip. A portion of land that has slid down in consequence of disturbance by an earthquake, or from being undermined by water washing away the lower beds which supported it.