38 



CARBONIFEROUS LIMESTONE. 



as defences when the fish was attacked by the powerful cephalopods which 

 inhabited the ocean at the period of its existence." The head and body are 

 covered with scales, of peculiar and varied shapes. Ansted. 



4. The carboniferous limestone, also called mountain limestone, 

 and metalliferous limestone, affords several varieties of black, 

 bluish grey, and variegated marbles, as well as ores of lead, cop- 

 per, zinc, &c. It contains a great number of organic remains, 

 such as divers polyparia cyathophylla (Jig. 18), madrepora, &c., 

 encrinites, which belong to the division of crinoidea (fig. 30). 



It also contains the remains of a number of mollusks, as the 

 orthoceras lateralis (fg. 31) ; goniatites (Jig- 32), which resem- 

 ble the nautilus ; bcllerophons (Jig- 33), which, with analogous 

 forms, are not chambered ; euompJialus (fig. 34) ; spirifers and 

 productus in great variety, especially (Jigs. 35, 36). 



The Crinoideae, (from the Greek, krinon^ a lily, and eidos, resemblance,) 

 a family belonging to the class of radiate animals, are remarkable for the 

 simplicity of their organization, and the peculiarly com- 

 plicated structure of their skeleton. The animal resem- 

 bled a true polyp or coral animalcule ; the body consisted 

 of a gelatinous tube, contracted at one extremity, by 

 which it was attached, and furnished at the opposite end 

 with a variable number of delicate contractile filaments 

 placed around the opening which represents the month. 



The calcareous skeleton was formed within the tube, 

 and consisted of thousands of regularly-shaped pieces, 

 kept together by the tough membrane which enclosed 

 them during the life of the animal. 



The family is divided into genera, according to the 

 form of the stems, or according to its general shape. 

 When the arms or stems are round, it is an Encrinite ; 

 Pi s 30 Cwitho- tne cyathocrinites (Jig. 30) takes its name from the 

 crinites planus. ' Greek , kuathos, a cup, and krinon, lily. 



Many limestones are composed almost exclusively of 



the remains of species of Crinoidea, as at Lockport, New York; and various 

 genera of this family are found in Alabama, near Huntsville. 



Th*e Orthoceras, or orlhoceratite, (from the Greek, orthos, 

 straight, and keras, horn,) is straight, or slightly bent, cylin- 

 drical, slightly conical, many-chambered cell ; the chambers 

 are separated by plain septa, which are concave towards the 

 larger end, and pierced with a siphuncle. 



Go'niatites (Jig. 32), (from the Greek, 

 gonia, an angle,) is a genus of extinct 

 cephalopods, which inhabited a cham- 

 bered shell resembling that of the am- 

 monites. 



Belle'ropTion (fig.W), (from the Greek, 

 Bellerophontes, the name of a fabulous 

 hero,) a genus of cephalopods which in- 

 Fig.31. Ortho- habited chambered shells similar to those 

 ceras lateralis. of the argonaut and nautilus. 



Fig. 32.Go'ma. 

 tiles evolutus. 



4 What are the characters of tne carboniferous Umestone ' 



