256 THE OPEN BOOK OF NATURE 
Corolla: A whorl of petals between the calyx and stamens, 
usually coloured. 
Corollifioree : Dicotyledonous plants whose petals are united and 
bear the stamens. 
Cotyledons : Seed-lobes. 
Orenate : Having rounded teeth on the margin. 
Cretaceous : The highest system of the Mesozoic rocks. 
Crinoids : Sea-lilies. 
Crustacea: An order of Arthropod animals, including crabs, 
lobsters, water-fleas, etc. 
Cuneate : Wedge-shaped. 
Cycads : Plants allied to the pines, but resembling palms and 
tree-ferns. 
Cystideans : Animals allied to the sea-lilies. They flourished in 
Cambrian and Silurian times. 
Deinocerata : A group of extinct mammals. 
Deinosaurs : An extinct order of reptiles. 
Deinotherium : A huge extinct animal which possessed two large 
tusks in the lower jaw. 
Dentate : Having marginal teeth, triangular and pointed. 
Devonian : Term applied to a system of rocks of Palzozoic age. 
Diatoms : One-celled Algee possessing flinty shells. 
Dicotyledons : Plants having seeds with two lobes. 
Dip : In geology, the angle at which strata incline. 
Dipterus : A fish of Old Red Sandstone age. 
Dyke : A mass of igneous rock intruded into a fissure of other 
rocks and often standing out like a wall. 
Echinodermata: A class of animals, like sea-urchins and star-fish, 
having skins strengthened by spiny plates or hard granules. 
Elliptical ; In botany, oval, but acutely pointed at each end. 
Entire : In botany, having an unbroken margin. 
Entomology : The science which relates to insects. 
Envelope : In botany, the outer whorl or whorls of the flower, 
the perianth. 
Eocene : The lowest system of the Cainozoic Era. 
Eozoie : The oldest of the four geological eras. 
Erect : Rising immediately to an upright position. 
Fault: A break in the continuity of beds of rock. 
Felspars : A family of minerals entering largely into the forma- 
tion of igneous rocks. 
Fertile : Fruit-bearing. 
Filament ; In botany, the stalk of the stamen bearing the anther. 
Flint : An impure form of silica. 
Foraminifera: Tiny one-celled animals possessing perforated 
shells of carbonate of lime. 
