440 GLOSSARY. 



Segments. — The transverse rings of which the body of an articulate 

 animal or Annelid is composed. 



Sepals. — The leaves or segments of the calyx, or outermost envelope of 

 an ordinary flower. They are usually green, but sometimes brightly 

 coloured. 



Serratures. — Teeth like those of a saw. 



Sessile. — Not supported on a stem or footstalk. 



Silurian System. — A very ancient system of fossiliferous rocks belonging 

 to the earlier part of the Palaeozoic series. 



Specialisation. — The setting apart of a particular organ for the perform- 

 ance of a particular function. 



Spinal Chord. — The central portion of the nervous system in the Verte- 

 brata, whic'i descends from the brain through the arches of the ver- 

 tebrae, and gives off nearly all the nerves to the various organs of the 

 body. 



Stamens. — The male organs of flowering plants, standing in a circle within 

 the petals. They usually consist of a filament and an anther, the 

 anther being the essential part in which the pollen, or fecundating 

 dust, is formed. 



Sternum. — The breast-bone. 



Stigma. — The apical portion of the pistil in flowering plants. 



Stipules. — Small leafy organs placed at the base of the footstalks of the 

 leaves in many plants. 



Style. — The middle portion of the perfect pistil, which rises like a column 

 from the ovary and supports the stigma at its summit. 



Subcutaneous. — Situated beneath the skin. 



Suctorial. — Adapted for sucking. 



Sutures (in the skull). — The lines of Junction of the bones of which the 

 skull is composed. 



Tarsus (pi. Tarsi). — The jointed feet of articulate animals, such as Insects. 



Teleostean Fishes. — Fishes of the kind familiar to us in the present day, 

 having the skeleton usually completely ossified and the scales horny. 



Tentacula or Tentacles. — Delicate fleshy organs of prehension or touch 

 possessed by many of the lower animals. 



Tertiary. — The latest geological epoch, immediately preceding the esta- 

 blishment of the present order of things. 



Trachea. — The wind-pipe or passage for the admission of air to the lungs. 



Tridactyle. — Three-fingered, or composed of three movable parts attached 

 to a common base. 



Trilobites. — A peculiar group of extinct Crustacean.;, somewhat resembling 

 the Woodlice in external form, and, like some of them, capable of rolling 

 themselves up into a ball. Their remains are found only in the Palaeo- 

 zoic rocks, and most abundantly in those of Silurian age. 



Trimorphic. — Presenting three distinct forms. 



Umbellifer^e. — An order of plants in which the flowers, which contain 

 five stamens and a pistil with two styles, are supported upon footstalks 

 which spring from the top of the flower stem and spread out like the 

 wires of an umbrella, so as to bring all the flowers in the same head 

 Qimbel) nearly to the same level. {Examples, Parsley and Carrot.) 



