76 HISTORY OF BRITISH ZOOPHYTES. 



generally strengthened with a horny or calcareous axis, 

 enveloped with tlie gelatinous or creto-gelatinous crust, 

 in which the polypes are immersed, and wliich open on 

 the surface in a starred fashion with eight rays. 

 III. Heliaxthoida. — Polypes single, free, or permanently 

 attached, fleshy, naked, or encrusted with a calcareous 

 poli/pidom, the upper surface of which is crossed with 

 radiating lamella?; mouth encircled with tubulous 

 tentacula; stomach membranous, plaited ; intestine ; 

 anus ; oviparous ; the ovaries internal. 



