FOSSIL HYDROZOA. 155 



attached to some foreign body by its base ; sometimes it 

 forms a crust-like investment to shells (Hydradinia) ; some- 



Fig. 46. Recent Corynida. A, Portion of the colony of J'erigonimus minulus, with poly- 

 ]>ites and reproductive buds, enlarged about 25 diameters ; B, A single polypite of Bimeria 

 rcstita, greatly enlarged, showing the extension of the polypary upon the bases of the 

 tentacles. (After Allman.) 



times it is rooted in the sand of the sea-bottom. Usually 

 the polypary is horny in texture, but forms of Hydractinia 



