DIBRANCHIATA (Gr. dis; twice; bragchia, gill).  The order of Cephalopoda (comprising the Cuttle-fishes, &c.) in which only two gills are present.

DICERAS (Gr. dis, twice; keras, horn).  An extinct genus of Bivalve Molluscs.

DICTYONEMA (Gr. diktuon, a net; nema, thread).  An extinct genus of Polyzoa.

DICYNODONTIA (Gr. dis, twice; kuon, dog; odous, tooth).  An extinct order of Reptiles.

DIDYMOGRAPTUS (Gr. didumos, twin; grapho, I write).  A genus of Graptolites.

DIMORPHODON (Gr. dis, twice; morphe, shape; oduos, tooth).  A genus of Pterosaurian reptiles.

DINICHTHYS (Gr. deinos, terrible; ichthus, fish).  An extinct genus of Fishes.

DINOCERAS (Gr. deinos, terrible; keras, horn).  An extinct genus of Mammals.

DINOPHIS (Gr. deinos, terrible; ophis, snake).  An extinct genus of Snakes.

DINORNIS (Gr. deinos, terrible; ornis, bird).  An extinct genus of Birds.

DIPLOGRAPTUS (Gr. diplos, double; grapho, I write).  A genus of Graptolites.

DIPNOI (Gr. dis, twice; pnoe, breath).  An order of Fishes, comprising the Mud-fishes, so called in allusion to their double mode of respiration.

DIPROTODON (Gr. dis, twice; protos, first; odous, tooth).  A genus of extinct Marsupials.

DIPTERA (Gr. dis, twice; pteron, wing).  An order of Insects characterised by the possession of two wings.

DISCOID (Gr. diskos, a quoit; eidos, form).  Shaped like a round plate or quoit.

DOLOMITE (named after M. Dolomieu).  Magnesian limestone.

DORSAL (Lat. dorsum, the back).  Connected with or placed upon the back.

DROMATHERIUM (Gr. dromaios, nimble; therion, beast).  A genus of Triassic Mammals.

DRYOPITHECUS (Gr. drus, an oak; pithekos, an ape).  An extinct genus of Monkeys.

ECHINODERMATA (Gr. echinos; and derma, skin).  A class of animals comprising the Sea-urchins, Star-fishes, and others, most of which have spiny skins.

ECHINOIDEA (Gr. echinos; and eidos, form).  An order of Echinodermata, comprising the Sea-urchins.

EDENTATA (Lat. e, without; dens, tooth).  An order of Mammalia often called Bruta.

EDENTULOUS.  Toothless, without any dental apparatus.  Applied to the mouth of any animal, or to the hinge of the Bivalve Molluscs.

ELASMOBRANCHII (Gr. elasma, a plate; bragchia, gill).  An order of Fishes, including the Sharks and Rays.

ENALIOSAURIA (Gr. enalios, marine; saura, lizard), Sometimes employed as a common term to designate the extinct Reptilian orders of the Ichthyosauria and Plesiosauria.