MANUAL OF NATURAL HISTORY. 357 



12. Family. — Mushroom-Corals (Agariciidse). Poly- 

 pary hard ; polyp-cells shallow, not circum- 

 scribed, but scattered and united to one 

 another by laminae on the star-bearing sur- 

 face of the coral ; animal growing laterally, 

 forming a leaf-like frondose mass. 



III. ORDER. — Asteroid-Polyps (Asteroida). 



Polyps compound ; tentacles eight, fringed ; sto- 

 mach membranous, with internal appendages; ovules 

 produced interiorly ; polypary free or fixed, fleshy, 

 strengthened by a horny or calcareous axis, covered 

 with a gelatinous crust. 



1. Family. — Alcyonians (Alcyoniidse). Polypary 



fixed, coriaceous or fleshy, strengthened with 

 calcareous spicula ; polyp-cells subcutaneous, 

 scattered over the surface. 



2. Family. — Sea-Pens (Pennatulidse). Polypary 



free, pennate, fleshy ; axis bony, simple, con- 

 tinuous ; skin spiculiferous ; polyps with eight 

 pinnate tentacles, arranged along margin of 

 pinnae. 



3. Family. — Umbellate - Corals (Umbellulariidae). 



Polypary free, simple, elongated, with the 

 polyps at the summit ; axis stony, inarticu- 

 late, covered with a fleshy cortex; polyps 

 large, terminal, arranged in an umbellate 

 manner at the end of the polypary. 



4. Family. — Calcareous-Corals (Coralliidse). Poly- 



pary fixed, arborescent, calcareous; covered 



