570 GLOSSARY. 



zoon; the opposite, or "proximal," extremity growing less rapidly, and 

 being the end by which the organism is fixed, when attached at all. 



DIURNAL (Lat. dies, day). Applied to animals which are active during the 

 day. 



DORSAL (Lat. dorsum, back). Connected with the back. 



DORSIBRANCHIATE (Lat. dorsum, the back ; Gr. bragchia, gill). Having ex- 

 ternal gills attached to the back ; applied to certain Anneiides&nd Mollusca. 

 The term is of mongrel composition, and " notobranchiate" is more cor- 

 rectly employed. 



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. 



ECHINULATE. Possessing spines. 



ECTOCYST (Gr. ektos, outside ; kustis, a bladder). The external investment of 

 the coencecium of a Polyzob'n. 



ECTODERM (Gr. ektos, and derma, skin). The external integumentary layer of 

 the Ccelenterata. 



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. 



EDRIOPHTHALMATA (Gr. hedraios, sitting ; ophthalmos, eye). The division 

 of Crustacea in which the eyes are sessile, and are not supported upon 

 stalks. 



ELASMOBRANCHII (Gr. elasma, a plate ; bragchia, gill). An order of Fishes, 

 including the Sharks and Rays. 



ELYTRA (Gr. elutron, a sheath). The chitinous anterior pair of wings in 

 Beetles, which form cases for the posterior membranous wings. Also ap- 

 plied to the scales or plates on the back of the Sea-mouse (Aphrodite). 



EMBRYO (Gr. en, in ; bruo, I swell). The earliest stage at which the young 

 animal is recognisable in the impregnated ovum. 



ENALIOSAURIA (Gr. enalios, marine ; saura, lizard). Sometimes employed as 

 a common term to designate the extinct Reptilian orders of the Jchthyosauria 

 and Plesiosauria. 



ENCEPHALOUS (Gr. en, in ; kephale, the head). Possessing a distinct head. 

 Usually applied to all the Mollusca proper, except the Lamellibranchiata. 



ENDOCYST (Gr. endon, within ; kustis, a bag). The inner membrane or in- 

 tegumentary layer of a Polyzob'n. In Cristatella, where there is no " ecto- 

 cyst," the endocyst constitutes the entire integument. 



ENDODERM (Gr. endon; aud derma, skin). The inner integumentary layer of 

 the Ccelenterata. 



ENDOPODITE (Gr. endon ; and pous, foot). The inner of the two secondary 

 joints into which the typical limb of a Crustacean is divided. 



ENDOSKELETON (Gr. endon; and skeletos, dry). The internal hard structures, 

 such as bones, which serve for the attachment of muscles, or the protec- 

 tion of organs, and which are not a mere hardening of the integument. 



ENSIFORM (Lat. ensis, a sword ; forma, shape). Sword-shaped. 



ENTOMOPHAGA (Gr. entoma, insects ; phago, I eat). A section of the Marsu- 

 pialia. 



ENTOMOSTRACA (Gr. entoma, insects ; ostrakon, a shell). Literally Shelled 

 Insects, applied to a division of Crustacea. 



ENTOZOA (Gr. enlos, within ; zoon, animal). Animals which are parasitic in 

 the interior of other animals. 



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. 



EPIDERMIS (Gr. epi, upon ; derma, the true skin). The outer non-vascular 

 layer of the skin, often called the scarf-skin or cuticle. 



