an 



[ 162] 



E K 



strata, and where they are found 

 they are abundant. 



EQUISE'TUM LYELLII. The name given 

 by Dr. Mantell to a distinct species 

 of equisetum, found in the grey and 

 blue grit and limestone at Pounce- 

 ford, in honour of Sir C. Lyell. 

 "When perfect, it probably attained 

 a height of two feet or more. 



EQUIVALENT, (from aequus and valens, 

 Lat.) In geology, where one bed 

 supplies the place of another which, 

 in that situation, is wanting, such 

 bed is called the equivalent of the 

 wanting bed. "When a stratum 

 suddenly terminates, and its place 

 is supplied by a stratum of a dif- 

 ferent character, the latter is called 

 the equivalent of the former. The 

 equivalents of compound substances 

 are the sums of those of their ele- 

 ments ; thus the equivalent of water 

 is (8 -fl = 9). 



E'auiVALE. (from aquus and valva, 

 Lat.) In conchology, when the 

 shells of bivalves are formed exactly 

 alike, as regards their length, width, 

 depth, &c. The shells of mya, solen, 

 tellina, &c., are generally of the 

 kind called equivalve, while those of 

 ostrea, pinna, &c., are inequivalve. 



E'RA. (<zra, Lat. Written frequently 

 <era.) A particular account and 

 reckoning of time and years, from 

 some remarkable event. Webster 

 quoting from some encyclopaedia, 

 says, " it differs from epoch in this; 

 era is a point of time fixed by some 

 nation or denomination of men; 

 epoch is a point fixed by historians 

 and chronologists. The Christian 

 era began at the epoch of the birth 

 of Christ." 



EBE'CTILE. (from erigo, Lat.) A 

 tissue peculiar to certain parts of 

 the body, as the nipple, &c. 



EBE'CT. (erectus, Lat.) In botany, 

 leaves are so called when they form 

 a very acute angle with the stem. 

 The term is also appiiecl to branches 

 rising in an upright direction, to 

 petioles rising nearly perpendi- 



cularly; and to flowers and pedi- 

 cles rising perpendicularly. 



E'BINITE. A name given to a species 

 of native arseniate of copper, from 

 its having been discovered in Ire- 

 land. It is of an emerald-green 

 colour; its constituent parts are 

 oxide of copper, arsenic acid, alu- 

 mina, and water. 



EEO'SE. | (erostis, Lat.) Jagged; 



EBO'SUS. ) applied to leaves very 

 irregularly cut or notched, and 

 having the appearance of being 

 gnawed or eaten by insects. 



EBO'TYLUS. A genus of insects, be- 

 longing to the Vivalpi, or the 

 seventh family of the Tetramera. 

 In the Erotyli the intermediate 

 joints of the antennae are almost 

 cylindrical, and the club, formed 

 by the last ones, is oblong; the 

 interior and corneous division of 

 their maxilla is terminated by two 

 teeth. They are peculiar to South 

 America. 



ERLNA'CEUS. (Lat.) The hedgehog. 



EBPETO'LOGY. (from epTrerb? and XoV/os, 

 Or.) That branch of natural his- 

 tory which treats of the structure, 

 habits, &c., of reptiles. 



EBRA'TIC BLOCK GROUP. One of the 

 sub-divisions of detrital deposits. 

 Professor Phillips observes, " In 

 the British islands, very consider- 

 able tracts of country have been 

 traversed, since the land had its 

 present general aspect of hill and 

 dale and was inhabited by large 

 quadrupeds, by currents of water 

 due to some unknown cause, which 

 transported rock masses with so 

 great a degree of force, to points 

 so elevated, in such directions, and 

 at such distances, that we cannot 

 avoid feeling extreme astonishment, 

 and look around in disappoinment 

 on the physical processes now at 

 work on the earth, for anything 

 similar. But it is only in particular 

 tracts that the magnitude of the 

 transported rocks is such as to 

 deserve the name of erratic Uocfo. 



