12 



Essmi introductori/ to Geology. 



ORDERS. 

 III. 



Tertiary order, 

 containing organic 

 remains of zoo- 

 pliytes,testacea,in- 

 sects, and niamnia- 

 lia, approximating 

 to the actually ex- 

 isting species. 



II. 



Secondary order, 

 containing marine 

 reraainSj differing 

 entirely in species, 

 . but approximating 

 in genera to those 

 actually existing, 

 thegeneraalsooften 

 extinct J terrestrial 

 animals very rarely 

 discovered ; sauri- 

 ans very abundant. 

 Cycadese prevail 

 among the vege- 

 tables. 



FORMATIONS. 



'"Pleiocene 

 {-§^ recent species. 



The Formations constituting 

 these groupes have too many 

 local variations to admit of 

 synoptical arrangement. 



Meiocene 



.p'p9jj recent species. 



Eocene 

 -To^ recent species. 



fChalk. 



("Cretaceous groupe. >^ Upper green sand. 



L Lower green sand. 



The lacustrine sands and limestone of 

 the Weald are occasionally interposed. 



f Upper Portland oolite, reposing 

 j on Kimmeridge clay. 



\ Oolitic groupe. -^ Middle oolite, or coral rag, re- 

 j posing on Oxford clay. 



LLower, or Bath oolite, reposing 

 on lias. 



rMuschelkalk, or conchite. 



,, ... . Variegated sand and marl, with 



L Poecihtic groupe. \ g^, ^^^^ g-^y^^xx^, or pcecilite. 



(_Zechstein magnesian limestone, 

 or dolomite. 



I. 



Inferior order, or 

 transition and pri- 

 mitive ; the upper 

 groupes containma- 

 rine zoophytes, tes- 

 tacea, and fish, of 

 which the genera as 

 well as species are 

 mostly extinct, and 

 differ very widely 

 from tiie actual 

 types. The lowest 

 groupe is nonfossil- 

 iferous. 



("Carboniferous 

 groupe. 



pCoal measures. 



J Mountain, or carboniferous 

 I limestone. 



L Old red sand stone. 



Grauwacke,orClas- 

 moschistose groupe 

 First appearance of K 

 organic remains. 



rUpper grauwacke, with Dudley 

 limestone, abundant in fossils. 



Middle grauwacke. 



Micaschistose 

 groupe; uon 

 fossiliferous. 



Lower grauwacke, or roofing 

 I slate of Cornwall and Snow- 

 L don, with few fossils. 



f Micaceous and other nonfossil- 

 iferous slates and primitive 

 I marble. 



I Gneiss. 



^Granite. 



