344 



ANIMALS OF THE PAST 



ages, and varied from less than an inch to two feet in 

 length. They were exceedingly abundant in the first half 



of this era, but later 

 slowly declined in num- 

 bers and variety until 

 they passed out of exist- 

 ence by the beginning of 

 the mesozoic era, never 

 to reappear. 



Lamp shells. — Perhaps 

 the next most important 

 group of animals was the 

 lamp shells, or brachio- 



FiG. 219. — Honeycomb coral. 



pods. They were also very numerous in the seas at this 

 time. This group differs from the trilobites in never hav- 

 ing entirely passed out of existence, because some species, 

 almost unchanged, are living at the present day. 



Corals. — There were corals also in those days. These 

 were mainly of three kinds : the cup corals, honeycomb corals, 

 and the chain corals. 

 Their names indicate 

 something of their 

 shape and appear- 

 ance. The cup corals 

 were single, solitary 

 polyps or groups of 

 polyps, each more or 

 less cup-shaped (Fig. 



218). The honey- Fig. 220. — Chain coral. 



comb corals were groups of polpys, each more or less 

 polygonal in shape, hence resembUng a honeycomb (Fig. 

 219). The appearance of the chain corals may be seen 



