GLOSSARY. 401 



DIATOMACE^ (Gr. diatemno, I sever). An order of minute 



plants which are provided with siliceous envelopes. 

 DIBRANCHIATA (Gr. dis, twice; bragchia, gill). The order of 



Cephalopoda (comprising the Cuttle-fishes, etc.,) in which only 



two gills are present. 

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



Bivalve Molluscs. 

 DICTYONEMA ( Gr. diktuoH, 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; 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, com- 

 prising 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 



characterized 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 Mam- 

 malia often called Bruta. 



EDENTULOUS. Toothless, without any dental apparatus. Applied 

 to the mouth of any animal, or to the hinge of the Bivalve 

 Molluscs. 

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