16 



University Geological Survey of Kansas. 



together. It has a very different external aspect from the 

 specimens of the form above mentioned from the same place, 

 and is probably a different species, but until specimens can be 

 secured showing the internal characters, it is referred provi- 

 sionally to this species. 



ANTHOZOA. 



Corals are exclusively marine animals. The reef-building 

 corals are found in comparatively shallow water, while some 

 other forms are found as deep as 1500 fathoms. The corals here 

 treated are all closely related to the reef-building forms, and 

 consequently indicate that the rocks in which they were formed 

 w^ere laid down in shallow water. The coral is an animal with a 

 distinct digestive sac and body cavity. There are three layers of 

 the body walls — the outer layer or ectoderm, the middle layer 

 or mesoderm, and the inner layer or endoderm. The hard parts 

 or skeleton are deposited by the inner layer between the inner 

 layer and the middle layer. This hard part forms a complete 

 layer around the lower part of the animal beneath the skin. 

 There are thin walls of the hard part projecting inward in the 

 folds of the mesentery. These walls are called septa. There 

 are often cross-plates or table- 

 like platforms across the lower 

 part of the hard parts extend- 

 ing clear across the body ; these 

 are called tabulae. Around the 

 mouth of the polyp, as the ani- 

 mal is called, there is a row of 

 tentacles, or feelers, which are 

 used to create currents of water 

 and assist in securing food. 



Corals very often increase by 

 budding ; that is, by a little 

 bud-like projection growing out 

 of one side of a coral and in a 



Fig. 1. 



Transverse section of a simple coral 

 (after Nicholson), s, septum ; c, columella. 



