676 



GEOLOGY. 



singularly rich in characteristic organic remains, 

 Euomphalus, so named from 

 the deeply umbilicated cha- 

 racter of the disk. These 

 are univalve shells, internally 

 divided into a series of par- 

 titions. As the animal in- 

 creased in size, it deserted 

 the innermost and smallest 

 chamber, which was left 

 vacant, and secreted a par- 

 tition wall behind it; and 

 as this process transpired at 

 different stages 

 of its growth, se- 

 veral successive 

 chambers were 

 formed. Those 

 singular tenants 

 of the deep, the 

 Encrinites, be- 

 longing to the 

 natural order of 

 Crino'ideans, or 

 lily-shaped ani- 

 mals, of several 

 varieties, occur, 

 whose remains 

 are so abundant 

 in the ancient strata 

 as to constitute forma- 

 tions many miles in 

 extent and of a con- 

 siderable thickness, 

 entirely consisting of 

 their calcareous ske- 

 letons. The animal is 

 thus defined by Mr. 

 Miller : " A round, 

 oval, or angular co- 

 lumn, composed of 

 numerous articulating 

 joints, supporting at 

 its summit a series of 

 plates or joints, which 

 form a cup-like body, 

 containing the viscera, 

 from whose upper rim L ne 



Giro. *' 2 - Cyathocrinites goniodactylus 



nve artlCU- 3 . Cyathocrinites capillaris. 



nrrna ^ 5 A ,* r, 4. Hypanthocrinites decorus. 



armb, dividing 5< Dimerocrinites icosidactylus. 



among which are several species of 



into tentaculated fingers, 

 more or less numerous, 

 surrounding the aperture 

 of the mouth." The two 

 genera which have at- 

 tracted most attention are 

 those with a circular stem, 

 or Encrinites, most nearly resembling 

 the external form of the lily ; and the 

 Pentacrinites, which have the stem 

 pentagonal. The engravings repre- 

 sent some of the Silurian varieties. 

 All the species in the older rocks 

 have the circular stem, with but one 

 exception; and all became extinct 

 before the formation of the lias, new 

 groups succeeding, which have now 



