266 HISTORY OF BRITISH ZOOPHYTES. 
II. Hypocrerta. 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- 
hiated.— Dr. Johnston. 
I. POLYZOA INFUNDIBULATA. 
The families and genera are thus arranged :— 
* Polypidoms calcareous; the cells tubular, with a round 
terminal aperture, uncovered with an operculum. Tv- 
BULIPORINA. 
Family I. Polypidoms multiform, massive or crustaceous. 
TUBULIPORIDA. 
Polypidom wart-like, with a defined base; the cells 
sub-erect, aggregated, or imperfectly rowed. Tusu- 
LIPORA. 
Polypidom crustaceous, undefined; the cells horizontal, 
semi-alternate. D1asTopora. 
Polypidom erect, branched; the cells opening all round, 
semi-alternate or irregular. PusruLipora. 
Polypidom dichotomous; the segments free; cells in 
alternating cross-rows on one surface. JDMONEA. 
