44° 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, which 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 Crustaceans, 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 

 (umbel) nearly to the same level. (Examples, Parsley and Carrot.) 



