E 



[157] 



E C 



traca are both dentated and eden- 

 tated ; they are mostly microscopic, 

 they are without exception aquatic, 

 and they mostly, though not with- 

 out exceptions, inhabit fresh water. 

 This order of crustaceans has the 

 head rarely, if ever, distinct from 

 the thorax, but provided with 

 antennae. Feet always distinct. 

 Animals undergoing metamorpho- 

 sis. Mr. Rupert Jones first noticed 

 the occurrence of Entomostraca in 

 the Permian system of England. 

 During the Permian period, the 

 prevailing forms of Entomostraca 

 seem to have belonged to two 

 groups, to Bairdia, and to an un- 

 determined genus. The list of 

 Permian entomostraca is now 

 rather extensive ; the Permians of 

 Durham possess a list of 21 species, 

 13 of which are peculiar to them. 

 Five species are peculiar to Ger- 

 many, and six to Russia. 



ENTQMO'TOMY. (from eWo/*a, an 

 insect, and TG^J/W, to cut, Gr.) 

 The dissection of insects, by which 

 we learn their internal construc- 

 tion, and become acquainted with 

 the form and texture of their 

 organs. 



ENTOZO'A. (from eVros and an), Gr.) 

 Intestinal worms. 



E'NTEOCHAL. (from entrochite.) Re- 

 sembling an entrochite j containing 

 entrochites. 



E'NTROCHITE. (from eV and i-po^os, 

 Gr.) Wheel-stone ; a name given 

 to the broken stems of fossil en- 

 crinites. Some beds of mountain 

 limestone are almost entirely com- 

 posed of broken stems and branches 

 of encrinites, frequently called 

 entrochites. The detached verte- 

 bra of the radiaria are known 

 by the name of trochitaB ; and 

 when several are united together, 

 so as to form part of a column, the 

 series is termed an entrochite. The 

 perforations in the centre of the 

 vertebra afford a facility for 

 stringing them as beads, from 



which, in ancient times, they were 

 used as rosaries, and in the northern 

 parts of England they still continue 

 to be known under the name of 

 St. Cuthbert's beads. 



(from j]u><$, aurora, and 

 os, recens, because, as Sir C. 

 Lyell observes, the very small 

 proportion of living species con- 

 tained in these strata indicates 

 what may be considered the dawn, 

 or first commencement, of the 

 existing state of the animate cre- 

 ation.) M. Deshayes and Sir C. 

 Lyell, have proposed a fourfold 

 division of the marine formations 

 of the tertiary series, founded on 

 the proportions which their fossil 

 shells bear to marine shells of 

 existing species. To these di- 

 visions Sir C. Lyell has, with the 

 soundest judgment, applied the 

 terms Eocene, Miocene, Older Plio- 

 cene, and Newer Pliocene, and well 

 would it be for the advancement of 

 geology, if its nomenclature were, 

 in all instances, derived from 

 some universal language. In fully 

 explaining the meaning of these 

 terms, I shall borrow largely from 

 Sir C. Lyell's Principles of Geology. 

 In proportion as geological investi- 

 gations have been extended over a 

 larger area, it has become necessary 

 to intercalate new groups of an age 

 intermediate between those first 

 examined; and we have every 

 reason to believe that, as the 

 science advances, new links in the 

 chain will be supplied, and that the 

 passage from one period to another 

 will become less abrupt. All those 

 geological monuments are by Sir 

 C. Lyell called tertiary, which are 

 newer than the secondary forma- 

 tions, and which, on the other 

 hand, cannot be proved to have 

 originated since the earth was in- 

 habited by man. All formations, 

 whether igneous or aqueous, which 

 can be shewn, by any proofs to be 

 of a date posterior to the intro- 



