E O C 



E P I 



most remote historical eras, must be very 

 great, embracing perhaps myriads of 

 years. There are no data for supposing 

 that there is any break, or strongly 

 marked line of demarcation, between the 

 strata of this and the recent epoch ; but, 

 on the contrary, the monuments of the 

 one seem to pass insensibly into those of 

 the other. 



The Older Pliocene strata contain 

 among their fossil shells a large propor- 

 tion of recent species, amounting to 

 nearly one-half. Thus out of 569 species 

 examined from Older Pliocene strata in 

 Italy, 238 were found to be still belonging 

 to living, and 331 to extinct, or unknown, 

 species. 



The next division of the marine for- 

 mations of the tertiary period is the 

 Miocene, from /weiwv, minor, and KCUVOG, 

 recens. In this division a small minority, 

 less than eighteen per centum, of fossil 

 shells being referable to living species. 

 From an examination of 1021 shells of 

 the Miocene period, M. Deshayes found 

 176 only to be recent. As there are 

 some fossil species which are exclusively 

 confined to the Pliocene, so are there 

 many shells equally characteristic of the 

 Miocene period. The Miocene strata are 

 largely developed in Touraine, and in the 

 South of France, near Bourdeaux ; in 

 Piedmont ; in the basin of Vienna, and 

 other localities. 



The oldest division of the marine for- 

 mations of the tertiary period is the 

 Eocene, the derivation of which term is 

 given at the commencement of this ar- 

 ticle. To this era the formations, first 

 called tertiary, of the Paris and London 

 basins, are referable. The total number 

 of fossil shells of this period known when 

 the tables of M. Deshayes were con- 

 structed, was 1238, of which number 42 

 only are living species, being at the rate 

 of three and a half per centum. Of fossil 

 species, not known as recent, forty-two 

 were found to be common to the Eocene 

 and Miocene epochs. Of the present 

 geographical distribution of those recent 

 species which are found fossil, in forma- 

 tions of such high antiquity as those of 

 the London and Paris basins, there is 

 much of great interest and importance. 

 Of the forty-two Eocene species, which 

 occur fossil in England, France, and Bel- 

 gium, and which are still living, about 

 one -half now inhabit the seas within, or 

 near the tropics, and almost all the rest 

 are inhabitants of the more Southern parts 

 of Europe. 



As a summary of the preceding, the 

 numerical proportion of recent to extinct 

 species of fossil shells, in the four dif- 

 ferent tertiary periods, is as follows : 



Newer Pliocene period 90 to 95^ percen- 

 Older Pliocene period 35 to 50 I turn of 

 Miocene period .18 [ recent 



Eocene period . 3 J fossils. 



EPHE'MERA. (t^TjjUfpta, ex tiri et >;/ipa, 

 Gr.) Insects, so called from their short 

 term of life in their perfect state. Their 

 body is extremely soft, long, tapering, 

 and terminated posteriorly by two or 

 three long and articulated setse. The 

 antennae are very small and composed of 

 three joints, the last of which is very 

 long, and in the form of a conical thread. 

 The ephemera usually appear at sun-set, 

 in fine weather, in summer and autumn, 

 along the banks of rivers and lakes. The 

 continuation of their species is the only 

 function these animals have to perform, 

 for they take no food, and frequently die 

 on the day of their metamorphosis. In 

 another condition, as larvae, their exis- 

 tence is much longer, extending from two 

 to three years. In this first state they 

 live in water. 



EPHE'MERAL. ^ (c^T^uepoe, Gr. ephemere, 



EPHK'MERICK. $ Fr. effimero, It.) Of 

 transitory duration ; short-lived ; exist- 

 ing only one day. 



EPHE'MERON. (ifrmtpov, Gr. ephemeron, 

 Lat.) A creature whose existence lasts 

 but a day. 



E'PICARP. (from STH, upon, and Kap-rrbz, 

 fruit, Gr.) In botany, the outer skin of 

 fruits is called the epicarp, the fleshy sub- 

 stance, or edible portion, is termed the 

 sarcocarp, and the stone is called the 

 endocarp. 



EPIDE'RMAL. ) Composed of epidermis ; re- 



EPIDE'RMIC. $ lating to the epidermis ; 

 resembling the epidermis. 



EPIDE'RMIS. (7rifop/tu, Gr. epidermis, 

 Lat. epiderme, Fr. epidermide, It.) The 

 scarf-skin, or cuticle of animals. In 

 conchology, the outer skin or cuticle, 

 with which the exterior surface of many 

 of the univalve and bivalve shells is 

 covered. It is membranaceous, and re- 

 sembles the periosteum which covers the 

 bones of animals. This skin seems to be 

 formed entirely by the animal, and is 

 always met with in some species, and 

 never in others ; those shells with a 

 ragged surface have almost always an 

 epidermis. In some it is laminated, vel- 

 vety, fibrous, or rough ; in others it is 

 thin and pellucid, allowing the colours of 

 the shell to show through it. It often 

 falls off of its own accord, and without 

 any injury to the surface of the shell : 

 the beauty of many shells is hidden by 

 this outer coat. In botany, the outward 

 covering of plants : every plant is covered 

 by a skin, or membrane, analogous to the 

 scarf-skin that covers animal bodies ; 

 this epidermis varies in thickness, being 



