432 



EErORT OF THE StATE GeOLOGIST. 



Simple — consisting of a basal cup without a beak, to which 

 the flagellum or seta is articulated, usually by a double joint, 

 admitting of motion in only one plane. 



Compound — in which the seta is continuous with or articu- 

 lated to a basal mandible, and the cup or receptacle has a more 

 or less distinct beak. 



The use of these appendages is not known. Busk says: "These 

 whip-like appendages serve as defensive and cleansing organs, and 

 may be observed in almost constant motion, sweeping slowly and 

 carefully over the surface of the colony and removing whatever 

 might be detrimental," but as is the case with avicularia, only a 

 portion of the Bryoz^a are furnished with these appendages. 



Fig. 12. Showing various forms of mandibles (after Busk). 



The two kinds of appendages are frequently coexistent on the 

 same colony, as shown in figure 8, and surely it is not neces- 



