370 
Geology of Sydney. 
diorite and quartz-mica-diorite are varieties of typical 
diorite. 
Diprotodon ((Jr. dis , twice ; protos , first ; odons, gen. 
odontos , a tooth). A genus of extinct marsupials, of 
ffigantic size, that flourished in Australia in Pliocene 
times 
Dolerite (Gr. doler os , deceptive). A coarse-grained 
variety of Basalt. 
Dolomite (named after M. Dolomieu). Magnesian Lime- 
stone. 
Dorsal (Lat. dorsum , the back). Connected with or 
placed upon the back. 
Dyke. An injected mass of rock. 
Echinodermata (Gr. echinos , the hedgehog ; and derma , 
skin). A class of animals comprising the Sea-urchins, 
Star-fishes, and others, most of which have spiny skins. 
Elasmobranchii (Gr. elasma, a plate ; branchion , a gill). 
An order of fishes, including the Sharks and Bays. 
Eocene (Gr. eos , dawn ; kainos , recent). The lowest 
division of the Tertiary rocks, in which species of exist- 
ing shells are, to a small extent, represented. 
Equisetacese (Lat. equus , a horse ; seta , bristle). A group 
of Cryptogamous plants, commonly known as “ Horse- 
tails.” 
Favosites (Lat. favus, a honeycomb). A genus of Palaeo- 
zoic Tabulate Corals. 
Felspar. A group of minerals differing somewhat in form 
and composition. All are silicates of alumni a ; some 
contain potash, others soda, others lime or lime 
nnd soda. 
