384 APPENDIX. 



the cenolithic period. The short, anthropolithic period is indi- 

 cated by the line n 0. (Compare vol. ii. p. 14.) The height of the 

 separate fields corresponds with the relative length of the periods 

 indicated by them, as they may approximately be estimated from 

 the relative thickness of the neptunic strata deposited between 

 them. (Compare vol. ii. p. 22.) The archilithic and primordial 

 period alone, during which the Lanrentian, Cambrian, and Silurian 

 strata were deposited, was probably considerably longer than the 

 four subsequent periods taken together. (Compare vol. ii, pp. 10, 

 20). In all probability the two tribes of worms and Zoophytes 

 attained their full development during the mid-primordial period 

 (in the Cambrian system) ; the star-fishes and molluscs probably 

 somewhat later (in the Silurian system) ; whereas the articulata 

 and vertebrata are still increasing in variety and perfection. 



Plate VII. (Between pages 146 and 147, Vol. II.") 



Group of Animal-Trees (Zoophytes, or Coelenterata) in the 

 Mediterranean. On the upper half of the plate is a swarm of 

 swimming medusa and ctenophora ; on the lower half a few 

 bunches of corals and hydroid polyps adhering to the bottom 

 of the sea. (Compare the system of Zoophytes, vol. ii. p. 132, 

 and on the opposite page their pedigree.) Among the adher- 

 ing Zoophytes at the bottom of the ocean there is, below on 

 the right hand, a large coral-colony (1), which is closely akin 

 to the red precious coral (Bucorallium), and like the latter 

 belongs to the group of corals with eight rays (Octocoralla 

 Gorgonida) ; the single individuals (or persons) of the branching 

 stock have the form of a star with eight rays, consisting of eight 

 tentacles, which surround the mouth. (Octocoralla, vol. ii. p. 143). 

 Directly below and in front of it (quite below on the right), is a 

 small bush of hydroid polyps (2), belonging to the group of bell- 

 polyps, or Campanulari^ (vol. ii. p. 146). A larger stock of hydroid 

 polyps (3), belonging to the group of tube-polyps, or Tubullarias, 

 rises, to the left, on the opposite side, with its long thin branches. 

 At its base is spread a stock of silicious sponges (Halichondria) 



