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tiary strata, namely, those which 

 occur in the neighbourhood of 

 Paris. These were found to fill a 

 depression in the chalk, and to be 

 composed of different materials, 

 sometimes including the remains of 

 marine, sometimes of fresh-water 

 animals. The first discovery of 

 the tertiary strata in the Isle of 

 "Wight and south-east of England, 

 we owe to Mr. Webster. The 

 whole of the tertiary accumulations 

 are stratiform deposites, exhibiting 

 various kinds of lamination and 

 bedding. Previously to the com- 

 mencement of the present century, 

 the true nature of the tertiary for- 

 mations was unknown, the chalk was 

 considered the highest known rock, 

 and the tertiary deposites as mere 

 superficial sands, gravels, or clays. 



The organic remains of the ter- 

 tiary deposites of England agree 

 with those of the Paris basin, but 

 the mineral character of these de- 

 posites is extremely different, those 

 rocks, in particular, which are com- 

 mon to the Paris basin and central 

 France being wanting, or extremely 

 rare, in England. 



The tertiary system may be said 

 to constitute a series of formations 

 which link together the present 

 and the past ; while the more an- 

 cient tertiary deposites contain or- 

 ganic remains related to the se- 

 condary formations, the most re- 

 cent contain many existing species 

 of animals and plants, associated 

 with forms now extinct. The term 

 tertiary has been altogether dis- 

 approved of by some geological 

 authors. 



The tertiary strata have been 

 sub-divided by Sir C. Lyell and M. 

 Deshayes into four principal groups, 

 to which Sir C. Lyell has assigned 

 the terms eocene, miocene, pliocene, 

 and pleistocene ; each group being 

 characterized by the relative pro- 

 portion of recent and extinct spe- 

 cies of shells therein contained. 



Commencing from below up wards, 

 we find included in the tertiary 

 series. 1. The eocene, comprising 

 marine and fresh-water deposits, 

 including in the former, the cal- 

 caire grossier and the London clay ; 

 in the latter, the calcaire silicieux. 

 2. The miocene, comprising the fa- 

 luns of the Loire, marine deposits, 

 and sands, clays, lignites, &c., &c. ; 

 fresh- water deposits. 3. The plio- 

 cene, consisting of sub-apennine 

 marl, sub-apennine yellow sand* 

 English crag, marine deposits ; and 

 sands, clays, lignites, &c., fresh- 

 water formations. 4. Pleistocene, 

 in this, the most recent of the ter- 

 tiary deposits, we have limestone, 

 sand, clays, conglomerates, marls, 

 &c., containing marine fossils, be- 

 ing marine stratifications; and 

 sands, clays, sandstones, lignites, 

 &c., containing fresh-water fossils, 

 being fresh- water deposits. 



TE'SSELATED. (tesselatus, Lat. wrought 

 in chequer- work.) Chequered, like 

 a chess board. In conchology, ap- 

 plied to shells that are coloured iu 

 regular and defined patches. 



TE'SSULAK. A term applied to a sys- 

 tem of crystallization, not suscep- 

 tible of variation. The cube, te- 

 trahedron, and several other forms 

 belong to the tessular system. 



TE'STA. (testa, Lat. a shell.) 



1. Commonly applied to the shelly 

 covering of testaceous animals. 



2. In botany, the outer coat of the 

 seed. The seed, or ripened ovulum, 

 consists of coverings called integu- 

 ments or seed- coats, the outer of 

 which is called the testa. 



TESTA'CEA. (from testa, Lat. a shell.) 

 In the Linnaen system of natural 

 history, the third order of Vermes. 

 This order comprises all shell-fish, 

 arranged by Linnaeus under thirty- 

 six genera. The testacea differ 

 from the Crustacea in their compo- 

 sition; the calcareous part of the 

 shells of testacea being carbonate 

 of lime, whereas in the shells of 



2 K 



