460 THE ORIGIN OF SPECIES 



Larynx. — The upper part of the windpipe opening into the gullet. 



Laurentian. — A group of greatly altered and very ancient rocks, which 

 is greatly developed along the course of the St. Lawrence, whence 

 the name. It is in these that the earliest known traces of organic 

 bodies have been found. 



Leguminos^e. — An order of plants represented by the common Pease 

 and Beans, having an irregular flower in which one petal stands 

 up like a wing, and the stamens and pistil are enclosed in a sheath 

 formed by two other petals. The fruit is a pod (or legume). 



Lemurid^. — A group of four-handed animals, distinct from the Mon- 

 keys, and approaching the Insectivorous Quadrupeds in some of 

 their characters and habits. Its members have the nostrils curved 

 or twisted, and a claw instead of a nail upon the first finger of the 

 hind hands. 



Lepidoptera. — ^An order of Insects, characterized by the possession of 

 a spiral proboscis, and of four large more or less scaly wings. It 

 includes the well-known Butterflies and Moths. 



Littoral. — Inhabiting the seashore. 



Loess. — A marly deposit of recent (Post-Tertiary) date, which occu- 

 pies a great part of the valley of the Rhine. 



Malacostraca. — The higher division of the Crustacea, including the 

 ordinary Crabs, Lobsters, Shrimps, etc., together with the Wood- 

 lice and Sand-hoppers. 



Mammalia. — The highest class of animals, including the ordinary hairy 

 quadrupeds, the Whales and Man, and characterized by the produc- 

 tion of living young which are nourished after birth by milk from 

 the teats (MammcB, Mammary glands) of the mother. A striking 

 difference in embryonic development has led to the division of this 

 class into two great groups; in one of these, when the embryo has 

 attained a certain stage, a vascular connection, called the placenta, 

 is formed between the embryo and the mother; in the other this 

 is wanting, and the young are produced in a very incomplete state. 

 The former, including the greater part of the class, are called 

 Placental mamm,als; the latter, or Aplacental mammals, include the 

 Marsupials and Monotremes (Ornithorhynchus) . 



Mammiferous. — Having mammae or teats (see Mammalia). 



Mandibles in Insects. — The first or uppermost pair of jaws, which 

 are generally solid, horny, biting organs. In Birds the term is 

 applied to both jaws with their homy coverings. In quadrupeds 

 the mandible is properly the lower jaw. 



Marsupials. — ^An order of Mammalia in which the young are born in 



