676 



singularly rich in characteristic 

 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 

 proceed five articu 

 lated arms, dividing 



GEOLOGY. 



organic remains, among which arc 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 



