EPHEBE. 



[ 293 ] 



EPHEMI^.RID.E. 



the name griven to a layer whioli eoats 

 those portions of the ventiieles of the braiu 

 which are not connected \vith the prolonga- 

 tions of the pia mater — as the floor of the 

 fourth ventricle, the ar|neduct of Sylvius, the 

 floor and the sides of the third ventricle, 

 the fifth ventricle, with the roof, the ante- 

 rior and postin'ior cornua, and a considerable 

 part of the inferior cornua of the lateral 

 ventricles. It consists of deUcate ciliated (?) 

 pavement epithelium, situated either imme- 

 diately upon the cerebral substance, or npon 

 an intermediate layer of connective tissue, or 

 of a soft homogeneous or granular mass. The 

 Cells are nucteated, and vary in diameter 

 from 1-900 to 1-490" ; they sometimes eon- 

 tain pigment. 



The ependyma is considered by many 

 anatomists a portion of the arachnoid 

 membrane. Corpora amrjlacea are often 

 met with beneath it ; sometimes also brain- 

 sand. 



BiBL. KoUiker, Mikr. Anat. 



EPHE'BE, Fr.— A genus of Collema- 

 ceous Lichens, usually described in an imper- 

 fect state as species of Stiyonema, a supposed 

 genus of AlgjB. E. ptihescens has a hairy, 

 branched, cartilaginous frond, covering the 

 sm-face of damp sub;ilpiue rocks with a 

 blackish-brown felt ; tlie branches are subu- 

 late, and the plant is dicBcious ; some speci- 

 mens have the branches swoUen into spindle- 

 shaped receptacles, in which are imbedded 

 numerous conceptacks, opening by a pore, 

 lined with clavate theccs, each containing 

 eight unisepate sjwres ; other specimens 

 bear spherical or subovoid subapical j)?/c?< idia, 

 in which are immersed spermogonia, de- 

 Msciug by a pore, containing numerous 

 linear basidia (sterigmata), supporting very 

 slender oblong spertnntia. Two supposed 

 species of Stigonema, Ag. (atrovirens and 

 ??iammilIosiim). have been foimd in fruit as 

 perfect Epjhebce, by Thwaites. According 

 to Flotow, forms of this Lichen have been 

 described under many names by Kiitzing 

 and others. 



BiBL. Bornet, Ann. Sci. Naf. 3 

 ser. xviii. 15.3, pi. 7 ; Berk, and 

 Br. ^/»?. N. H. 1851, vii. 188 ; 

 Nvlander, Syn. pi. 2. figs. 1 & 7 ; 

 Leishton, Lich. Fl. G. B. 10. 



EPHELO'TA, Wright.— A 

 genus of marine Infusoria, fam. 

 Actinophryina (Acinetina, Clap. 

 and Lachm.), resembling Podo- 

 phrya, but the tentacles pointed 

 instead of capitate, and forming a 

 wreath or circlet. 



2 species. On Serfidaria, and in the 

 mouths of shells containing hermit-crabs. 



BiBL. Pritchard, Inf. p. 662; Wright, 

 Ed. New Phil Jn. 1858, p. 7. 



EPIIEM'ERA, Linn.— A genus of Neu- 

 ropterous Insects, of the family Ephemeridae. 



Char. Wings four ; posterior filaments 

 three ; head of larva with cornua. 



The larva and pupa are favourite micro- 

 scopic objects, for showing the dorsal vessel, 

 the circulation, branchial plates, &c. See 

 Ephemerit)^. 



EPlIEME'REzE.— A family of inoper- 

 culate Acrocarpous (terminal-fruited) Mos- 

 ses, usuallj' dwarf, caespitose, or gregarious. 

 Stem almost simple. Leaves more or less 

 oval or lanceolate, slightly concave, pellucid, 

 with or without nerves. Cells of the leaves 

 parenchymatous, lax in all parts, elongate, 

 not papillose. Capsule mostly obliquely 

 apiculated. 



British Genus. 



Ephcmencm. Calyptra campanulate. In- 

 florescence monoecious or dioecious (anthe- 

 ridia on a very short special brcanch situated 

 near the base of the stem). 



EPHEMERTD.E(May-flies).— Afamily 

 of Neuropterous Insects. 



Characterized by the minute size of the 

 antennfe ; the unequal size of the anterior 

 and posterior pairs of wings (the latter of 

 which are in some absent) ; the membra- 

 nous and almost obsolete mouth ; and the 

 elongated j ointed setfe at the posterior end 

 of tlie body. 



Body long, slender, and soft ; head small, 

 ti-ansverse-trigonate ; eyes large, nearly oval, 

 lateral ; ocelli three, forming a triangle be- 

 tween the eyes ; antennie three-jointed, the 

 two basal joints thick, the third forming a 

 long slender seta. Abdomen consisting of 

 nine joints; the terminal the longest, and 

 gradually narrowed and furnished at the 

 apex in both sexes with two or three long, 

 slender, many-jointed filaments. Legs 

 slender ; anterior pair in the males pon-ected, 

 much elongated, with the tibiae and tarsi 



Fig. 198, 



Ephemera Swammerdamii. Nat. size. 



