Diallage. A mineral.
Didelphys. A pouched animal, as the Opossum.
Dinosauria. Land lizards—only found fossil.
Dip (in Geology). The angle of inclination which the plane of a bed makes with the plane of the horizon.
Diplopterus, Diplodus, and Diplocanthus. Fishes of the Devonian or Old red sandstone.
Dipterus (having two wings). A fish of the Old red sandstone.
Dodo. A large bird once found in the Isle of France, but now extinct.
Dolomite. Crystalline carbonate of lime and magnesia.
Dyke. A rock, generally crystalline, occupying a rent or fissure in some other and older rock. A dyke differs from a mineral vein chiefly in its greater magnitude and in the absence of ramifications.
Dynamics (Gr., power). Used in mechanics.