E T H 



[ 164 ] E X C 



ETHE'EIA. A genus of large in- 

 equivalve molluscs belonging to the 

 family Ostracea. They differ from 

 the ostrese in having two elongated 

 muscular impressions in each valve, 

 which are united by a slender 

 palleal impression. The animal is 

 not known to produce a byssus. 



E'THMOID. (from ^fyto<?, a sieve, and 

 eios, like, Gr.) A bone of the 

 nose to which the name ethmoid 

 has been given from its being 

 cribriform, or perforated like a 

 sieve, for the passage of the olfac- 

 tory nerves. 



E'TITE. See Elites. 



E'TTUS. A genus of crustaceans, 

 some species of which have been 

 discovered in the gait. 



EUCHYSI'DEBITE. A mineral occurring 

 crystallized. Primary form, an 

 oblique rhombic prism of the same 

 cleavage and measurements as 

 pyroxene. Colour, brownish-black. 

 Lustre, vitreous; nearly opaque. 

 Specific gravity 3 -3 4, hardness 6 

 to 6-5. Streak, yellowish-grey. 

 Fracture, imperfect conchoidal. 

 Found in Norway. 



EU'CLASE. (from ei>, well, and K\aw t 

 to break, Gr.) The Prismatischer 

 Smaragd of Mohs ; Prismatic Eme- 

 rald. This stone has obtained its 

 name from the ease with which it 

 is broken. It is a rare and beau- 

 tiful mineral, and was brought 

 first from Peru by Dombey ; it was 

 at first confounded with the eme- 

 rald, in consequence of its green 

 colour. The primitive form of its 

 crystals is a rectangular prism, 

 whose bases are squares. It is of 

 sufficient hardness to scratch 

 quartz. Its constituents are silica, 

 alumina, glucina, and the oxides of 

 iron and tin. Euclase has hitherto 

 only been found crystallised. Spe- 

 cific gravity 3*06, hardness = 7*5 

 It is transparent, and possesses 

 strong double refraction. Before 

 the blow-pipe it first loses its 



transparency, and then fuses into 

 a white enamel. 



EUDI'ALITE. A mineral of a brown- 

 ish-red colour, having an octohedral 

 cleavage. 



E'UDOSIPHONITES. The same assigned 

 by Professor Ansted to a genus of 

 ammonites. See Aymenia. 



EUGE'JSTA GEINITES. (So named from 

 the Eugenia caryophyllata, or clove 

 tree, the unripe fruit of which it 

 resembles, and Kpivov, a lily.) A 

 genus of fossil crino'idea, six species 

 of which have been determined by 

 Goldfuss and Munster as occurring 

 in the oolitic group. 



EUKAI'EITE. Cupreous seleniuret of 

 silver, consisting of silver 39, se- 

 lenium 26, copper 23, alumina 8. 



ET/LISITE. A mixture of olivine-like 

 oxide of iron, green augite, and 

 brownish-red garnet. Jukes. 



EUO'MPHALUS. A univalve uncham- 

 bered fossil shell, found in the 

 mountain lime-stone. 



EU'PHOTIDE. ) Names given by the 



EU'PHOTITE. j French mineralo- 

 gists to Saussurite. A green stone 

 in which the hornblendic mineral 

 is diallage, and the feldspar labra- 

 dorite. 



EU'PODA. The name given in Cuvier's 

 "Begne Animale" to the fifth 

 family of Tetramerous Coleoptera ; 

 Eupoda comprises two tribes, Sag- 

 rides and Criocerides. 



EUEYPTE'EIDA. An order of crusta- 

 ceans, comprising eurypterus and 

 pterygotus, found fossil only. 



EU'EIIE. White-stone, the weiss- 

 stein of Werner. A variety of 

 granite in which feldspar predomi- 

 nates, and named Eurite by the 

 French mineralogists. It occurs 

 in beds, in common granite, in 

 Cornwall. In its most compact 

 form, it becomes a porphyry, and 

 is closely allied to volcanic rocks 

 in Auvergne; felspathic granite. 

 JBakewell. 



EXCE'BN. (excerno, Lai.} To excrete; 



