GLOSSARY. 355 
Digit (Lat. digitus, a finger). A finger or toe. 
DigiticRaDA (Lat. digitus, a finger; gradior, I walk). The divisionof 
Carnivora in which the animal walks upon the tips of the toes, 
DIPNoI (Gr. dis, twice; pnoe, breath). ‘The order of fishes represented 
by the Lepidosiren. 
DipTrERA (Gr. dis, twice ; pteron, a wing). An order of Insects character- 
ised by the possession of two wings only. 
DiscoPpHorRA (Gr. diskos, a quoit or round plate ; phero, I carry). The 
Medusce, or Jelly fishes, so called from their form. Also, the order of 
the Leeches (Hirudinea) from the suctorial dises which they possess. 
DistaL. Applied to the quickly-growing end of the hydrosoma of a 
fHydrozoén ; also to the end of a limb, or of any portion of a limb, fur- 
thest removed from the trunk. 
DIuRNAL (Lat. diurnus, daily, by day). Applied to animals which are 
active during the day. 
Dorsat (Lat. dorsum, the back). Connected with theregion of the back. 
ECHINODERMATA (Gr. echinos, a hedgehog; derma, skin). A class of 
animals comprising the Sea-urchins, Star-fishes, and others, most of 
which have spiny skins. 
ECHINOIDEA (Gr. echinos, a hedgehog ; eidos, form). An order of Echino- 
dermata, comprising the Sea-urchins. 
Kotocyrst (Gr. ektos, outside; kustis, a bladder). The external investment 
of the polypide of a Polyzoén. 
HoTopERM (Gr. ektos, outside ; derma, skin). The external integumentary 
layer of the Celenterata. 
EDENTATA (Lat. e, without; dens, tooth). An order of Mammalia in 
which some or all of the teeth are wanting. Often called Bruta. 
HLASMOBRANCHII (Gr. elasma, astrap ; bragchia, gill). An order of fishes, 
including the Sharks and Rays. 
EnytRa (Gr. elutron, a sheath). The hard chitinous anterior pair of wings 
in the Beetles, which form protective cases beneath which the posterior 
membranous wings can be folded. 
Enpocyst (Gr. endon, within; kustis, a bag). The inner membrane of 
the polypide of a Polyzoén. 
ENDODERM (Gr. endon, within; derma, skin). The inner integumentary 
layer of the Celenterata. 
ENDOSKELETON (Gr. endon, within; skeletos, dry). The internal hard 
structures, such as bones, which serve for the attachment of muscles, or 
the protection of organs, and which are not merely produced by a har- 
dening of the integument. 
ENTOMOSTRACA (Gr, entoma, insects ; ostrakon, shell), Literally, ,“‘ Shelled 
Insects ;”’ applied to a division of the Crustacea. 
EnToz0A (Gr. entos, within; zoén, animal), Animals which live parasiti- 
cally in the interior of other animals. 
EQUILATERAL (Lat. equus, equal; latus, side). Having its sides equal. 
Usually applied to the shells of the Brachiopoda. 
EQUIVALVE (Lat. wquus, equal; valve, folding-doors). Applied to shells 
which, like those of most of the Lamellibranchiata, are composed of two 
equal pieces or valves, 
ERRANTIA (Lat. erro, I wander). An order of Annelida, comprising forms 
which are capable of active locomotion. ' 
EURYPTERIDA (Gr. eurus, broad; pteron, wing). A group of extinct 
Crustacea. 
EXOSKELETON (Gr. exo, outside; skeletos, dry). Under this term are 
comprised all structures which are produced by a hardening of the 
integument, 
