20O HISTORY OP BRITISH ZOOPHYTES. 



II. HYPOCREPIA. Lacustrine or fresh-water. Polypes 

 compound; the mouth surrounded with ciliated retractile 

 tentacula, interrupted or depressed on one side, so as 

 to assume a crescentic or horse-shoe form : ova unci- 

 liated. Dr. Johiiston. 



I. POLYZOA INFUNDIBULATA. 



The families and genera are thus arranged : 

 Polypidoms calcareous ; the cells tubular, with a round 

 terminal aperture, uncovered with an operculum. Tu- 



BULIPORINA. 



Family I. Polypidoms multiform, massive or crustaceous. 



TuBULIPORIDyE. 



Polypidom wart-like, with a denned base; the cells 

 sub-erect, aggregated, or imperfectly rowed. TUBTJ- 



LIPORA. 



Polypidom crustaceous, undefined; the cells horizontal, 



semi-alternate. DIASTOPORA. 

 Polypidom erect, branched; the cells opening all round, 



semi-alternate or irregular. PUSTULIPORA. 

 Polypidom dichotomous ; the segments free ; cells in 



alternating cross-rows on one surface. IDMONEA. 



