344 



ANIMALS OF THE PAST 



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

 lenf^tli. They were exceechngly abundant in the first half 



of this era, but later 

 slowly declined in num- 

 bers and vai'iet)' until 

 they passed out of exist- 

 ence Ijy the beginning of 

 the mesozoic era, never 

 to reapiteai'. 



Lamp shells. — Perhaps 

 the next most important 

 group of animals was the 

 lamp shells, or brachio- 

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

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

 ing entirely passed out of existence, iiecause some species, 

 almost unchanged, ai'c living at the present day. 



Corals. — Tliere were corals also in those da^'s. These 

 were mainly of thre(dvinds : the cup corals, honeycomb corals, 

 and the chain corals. 



Fic. 219.— Ilcnev 





Their names indicate 



something of their 



shape and appeai- 



ance. The cup coi'als 



were single, sulitary 



].)olyps or groups of 



])olyps, each more or 



less cup-shaped (Fig. 



218). The honey- Fk^ 22o.-ciku„ romi. 



com]) corals were groups of poli)ys, each more or less 



polygonal in sha])e, hence reseml)ling a honeycomb (Fig. 



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



