GLOSSARY. 663 



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. 



ENCEPHALON (Gr. egcephalos, brain). The portion of the cerebro-spinal ner- 

 vous axis contained within the cranium. 



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

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



ENCYSTATION (Gr. en, in ; kustis, a bag). The transformation undergone by 

 certain of the Protozoa, when they become motionless, and surround them- 

 selves by a thick coating or cyst. 



ENDERON (Gr, en, in ; deros, skin). The inner plane of growth of the outer 

 integumentary layer (viz., the ectoderm or epidermis). 



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

 mentary layer of a Polyzoon. In Cristatella, where there is no " ectocyst," 

 the endocyst constitutes the entire integument. 



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

 the Ccelenterata. 



ENDOPODITE (Gr. endon; andjooit,?, foot). The inner of the two secondary 

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



ENDOSARC (Gr. endon ; and sarx, flesh). The inner molecular layer of sarcode 

 in the Amoeba, and other allied Rhizopods. 



ENDOSKELETON (Gr. endon ; and 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 a mere hardening of the integument. 



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



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

 pialia. 



ENTOMASTRACA (Gr, entoma, insects; ostrakon, a shell). Literally, shelled 

 insects applied to a division of Crustacea. 



ENTOZOA (Gr. entos, 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. 



EPIMERA (Gr. epi, upon ; meron, thigh). The lateral pieces of the dorsal arc 

 of the somite of a Crustacean. 



EPTPODIA (Gr. epi, upon ; pous, the foot). Muscular lobes developed from 

 the lateral and upper surfaces of the "foot " of some Molluscs. 



EPIPODITE (Gr. epi, upon ; pous, foot). A process developed upon the basal 

 joint, or "protopodite," of some of the limbs of certain Crustacea. 



EPISTERNA (Gr. epi, upon ; sternon, the breast-bone). The lateral pieces of 

 the inferior or ventral arc of the somite of a Crustacean. 



EPISTOME (Gr. epi ; and stoma, mouth). A valve-like organ which arches over 

 the mouth in certain of the Polyzoa. 



EPITHECA (Gr. epi ; and theke, a sheath). A continuous layer surrounding the 

 thecse in some Corals externally. 



EPIZOA (Gr. epi, upon ; zoon, animal). Animals which are parasitic upon 

 other animals. In a restricted sense, a division of Crustacea which are 

 parasitic upon fishes. 



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

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



