GLOSSARY. 385 



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



Reptiles. 



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

 DIMORPHODON (Gr. dis, twice ; morphe, shape ; odous, 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 com- 

 prising the Sea-urchins, Star-fishes, and others, most of which have spiny 

 skins. 



ECHINOIDEA (Gr. echinos ; and eidos, form). An order of Echinodermata, com- 

 prising 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 Plesiosatiria. 



EOCENE (Gr. eos, dawn ; kainos, new or recent). The lowest division of the 

 Tertiary rocks, in which species of existing shells are to a small extent 

 represented. 



EOPHYTON (Gr. eos, dawn ; phuton, a plant). A genus of Cambrian fossils, 

 supposed to be of a vegetable nature. 



EOZOON (Gr. eos, dawn ; zoon, animal). A genus of chambered calcareous or- 

 ganisms found in the Laurentian and Huronian formations. 



EQUILATERAL (Lat. aquus, equal ; latus, side). Having its sides equal. Usu- 

 ally applied to the shells of the Brachiopoda. When applied to the spiral 

 shells of the Foraminifera, it means that all the convolutions of the shell lie 

 in the same plane. 



EQUISETACE^: (Lat. equus, horse ; seta, bristle). A group of Cryptogam ous 

 plants, commonly known as "Horse-tails." 



EQUIVALVE (Lat. cequus, equal ; valvce, folding-doors). Applied to shells which 

 are composed of two equal pieces or valves. 



ERRANTIA (Lat. erro, I wander). An order of Annelida, often called Nereidea, 

 distinguished by their great locomotive powers. 



EUOMPHALUS (Gr. eu, well ; omphalos, navel). An extinct genus of Univalve 

 Molluscs. 



EURYPTERIDA (Gr. eurus, broad ; pteron, wing). An extinct sub-order of Crus- 

 tacea. 



EXOGYRA (Gr. exo, outside ; guros, circle). An extinct genus of Oysters. 



