268 HISTOllY OP BRITISH ZOOPHYTES. 



Polypidom crustaceous; cells in a single layer. 



LEPRALIA. 

 Polypidom crustaceous; cells quincuncial. MEM- 



BRANIPORA. 



Family V. Polypidoms multiform, composed of oblong 

 sub- quadrangular cells, disposed in semi-alternating 

 series j the cells conjunct, horizontal to the plane of 

 axis, with a subterminal or lateral aperture, usually 

 covered with an ovarian capsule. ESCHARHLE. 

 Polypidom foliaceous or membranous, composed of 

 several series of oblong sub-quadrangular cells, on 

 two planes, or one only. FLUSTRA. 

 Polypidom membrano-calcareous, frondescent; the cells 

 immersed, in a double layer placed back to back, 

 like the cells in honey-comb. ESCHARA. 

 Polypidom calcareous, frondescent, netted; the cells 



on the upper side only. RETEPORA. 

 Polypidom dichotomous, with jointed cylindrical 

 branches; cells immersed, rhomboid. SALICORNIA. 

 *** Polypidoms sponge-like, fleshy, polymorphous ; the 

 cells irregular in disposition, immersed, with a con- 

 tractile aperture ; no external ovarian capsules. HAL- 

 CYONELLEA, Ehretib. Cor all. 153. 



