T E R 



T E S 



they may be seen resting on granite. If 

 a new name were necessary, post-cre- 

 taceous should have been chosen ; as all 

 geologists are agreed that the tertiary 

 strata were deposited after the chalk." 



The tertiary strata have been sub- 

 divided by Mr. Lyell and M. Deshayes 

 into four principal groups, to which Mr. 

 Lyell has assigned the terms eocene, mio- 

 cene, older pliocene, and newer pliocene ; 

 each group being characterized by the 

 relative proportion of recent and extinct 

 species of shells therein contained. To 

 this nomenclature of Mr. Lyell's, Mr. De 

 La Beche urges the following objections. 

 " Classifications entirely founded on or- 

 ganic remains are at all times liable to be 

 erroneous, if contemporaneous deposition 

 be thence inferred as a necessary conse- 

 quence ; they therefore may be consi- 

 dered as doubly liable to error when em- 

 ployed in proving contemporaneous ori- 

 gin in such rocks as those of the supra- 

 cretaceous period, and which may contain 

 a certain per centage of the remains of 

 molluscs resembling those of the present 

 day. When we appropriate names of this 

 kind to rocks, derived from one character j 

 alone, and that character one which can- \ 

 not be considered constant, we theoreti- 

 cally prejudge the place which the rocks | 

 should occupy in a geological series, where 

 the comparative date of the deposit itself 

 is sought, not the particular proportion 

 of given organic remains detected in it, 

 which is necessarily a secondary consider- 

 ation. If it be considered convenient to 

 divide the supra-cretaceous rocks of Eu- 

 rope into three or more sub-groups, 

 names which imply their actual geological 

 position in the series, such as superior, 

 medial, and inferior ; upper, medial, and 

 lower, or others of the like kind, would 

 be preferable to those derived only from 

 a per- centage of certain organic con- - 

 tents." 



These little differences of opinion, how- 

 ever, between our leading geologists will ; 

 give place to the general advancement of 

 the science. A multiplied nomenclature 

 is greatly to be deprecated, leading not 

 only to much confusion, but being, in 

 itself, a source of discouragement to the 

 student, and deterring many from enter- 

 ing on the study of any branch of 

 science. 



Although the tertiary or supra-creta- 

 ceous formations may be said to include 

 all the deposits from the chalk upwards, 

 yet, by some geologists, those of what is 

 termed the recent period form a distinct 

 subdivision, and the tertiary formations 

 include only the four groups, namely, 

 the eocene, miocene, older pliocene, and 

 newer pliocene. Commencing therefore 



from below upwards, we find included in 

 the tertiary series, 1. The eocene, com- 

 prising marine and fresh-water deposits, 

 including in the former, the calcaire gros- 

 sier and the London clay, in the latter, the 

 calcaire siliceux. 2. The miocene, com- 

 prising the faluns of the Loire, marine 

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

 &c. ; fresh-water deposits. 3. The older 

 pliocene, consisting of subapennine marl, 

 subapennine yellow sand, English crag, 

 marine deposits ; arid sands, clay&, lig- 

 nites, &c., fresh- water formations. 4. 

 Newer pliocene. In this, the most recent 

 of the tertiary deposits, we have limestone, 

 sand, clays, conglomerates, marls, &c. 

 containing marine fossils, being marine 

 stratifications ; and sands, clays, sand- 

 stones, lignites, &c., containing fresh- 

 water fossils, being fresh-water de- 

 posits. 



TE'SSELATED. (tcsselatus, Lat. wrought 

 in chequer-work.) Chequered, like a chess 

 board. In oonchology, applied to shells 

 that are coloured in regular and defined 

 patches. 



TE'SSULAR. A term applied to a system 

 of crystallization, not susceptible of va- 

 riation. The cube, tetrahedron, and 

 several other forms belong to the tessular 

 system. 



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



1. Commonly applied to the shelly co- 

 vering of testaceous animals. 



2. In botany, the outer coat of the seed. 

 The seed, or ripened ovulum, consists of 

 coverings called integuments or seed- 

 coats, the outer of which is called the 

 testa. 



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

 testace', Fr.) In the Linneean system of 

 natural history, the third order of vermes. 

 This order comprises all shell-fish, ar- 

 ranged by Linnseus under thirty-six ge- 

 nera. The testacea differ from the crus- 

 tacea in their composition ; the calca- 

 reous part of the shells of testacea being 

 carbonate of lime, whereas in the shells 

 of Crustacea it is phosphate of lime. The 

 testacea also retain their shells as long as 

 they live ; the Crustacea cast them an- 

 nually, or, at least, periodically. 



TESTA'CEOUS. (testacms, Lat. testacee, 

 Fr. testaceo, It.) Belonging to the 

 order testacea ; having a strong thick 

 shell, the calcareous portion of which con- 

 sists of carbonate of lime. 



TESTACEO'LOGY. A modern term for the 

 natural history of shells, and synonymous 

 with conchology. 



TESTU'DINATE. ( testudineatus, Lat.) 

 Arched ; vaulted ; resembling the back 

 of a tortoise. 



TKSTU'DO. (testudo, Lat.) 



1. A genus of the order Chelonia; the 



