16 EXPLANATION OF THE FIGURES. 



FIG. 



150. Comatula, a West India species, in its early stage, with its stem. 



151. The same detached, and swimming free. 



152. Longitudinal section of the sturgeon, to show its cartilaginous ver- 



tebral column. 



153. Amphioxus, natural size, showing its imperfect organization. 



154. Section of the earth's crust, to show the relative positions of the 



rocks composing it ; E, plutonic or massive rocks ; M, metamor- 

 phic rocks ; T, trap rocks ; L, lava. 1. Lower Silurian forma- 

 tion ; 2. Upper Silurian ; 3. Devonian ; 4. Carboniferous ; 5. 

 Trias, or Saliferous ; 6. Oolitic ; 7. Cretaceous ; 8. Lower Terti- 

 ary or Eocene ; 9. Upper Tertiary, or Miocene, and Pleiocene ; 

 10. Drift. 



155. Fossils of the Paleozoic age ; a, Lingula prima ; b, Lepteena alter- 



nata ; c, Euomphalus hemisphericus ; d, Trocholites ammonius ; 

 e, Avicula decussata ; f, Bucania expansa ; g, Orthoceras fusi- 

 forme ; i, Cyathocrinus ornatissimus, Hall ; j, Cariocrinus orna- 

 tus, Say ; k, Melocrinus amphora, Goldf. ; I, Columnaria alveo- 

 lata ; m, Cyathophyllum quadrigeminum, Goldf. ; n, o, Caninia 

 fiexuosa ; p, Chseietes lycoperdon. 



156. Articulata of the Palaeozoic age ; a, Harpes ; b, Arges ; c, Brontes ; 



d, Platynotus ; e, Eurypterus remipes. 



157- Fishes of the Palaeozoic age ; a, Pterichthys ; b, Coccosteus ; c, 

 Dipterus ; d, palatal bone of a shark ; e, spine of a shark. 



158. Representations of the tracks of supposed birds and reptiles in the 



sandstone rocks. 



159. Supposed outlines of Ichthyosaurus, (a,) and Plesiosaurus, (6.) 



160. Supposed outline of Pterodactyle. 



161. Shells of the Secondary age ; a, Terebratula ; b, Goniomya ; c, 



Trigonia ; d, Ammonite. 



162. Supposed outline of the cuttle-fish, (a,) furnishing the Belemnite. 



163. Radiata from the Secondary age ; a, Lobophyllia flabellum ; b, Litho- 



dendron pseudostylina ; c, Pentacrinus briareus ; d, Pterocoma 

 pinnata ; e, Cidaris ; f, Dysaster ; ff, Nucleolites. 



164. Shells of the Cretaceous formation ; a, Ammonites ; b, Crioceras ; 



c, Scaphites ; d, Ancyloceras ; e, Karaites ; f, Baculites ; g, 

 Turrilites. 



165. Shells of the Cretaceous formation ; a, Magas ; b, Inoceramus ; c, 



Hippurites ; d, Spondylus ; e, Pleurotomaria. 



166. Radiata from the Cretaceous formation; a, Diploctenium cordatum; 



b, Marsupites ; d, Galerites ; c, Salenia ; e, Micraster cor- 

 anguinum. 

 167- Nummulite. 



168. Supposed outline of Paleotherium. 



169. Supposed outline of Anoplotherium. 



170. Skeleton of the Mastodon, in the cabinet of Dr. J. C. Warren. 



