ALCYONARIA: RENILLID^. 519 



According to Professor Verrill, Polyps embrace three 

 orders, Alcyonaria, Actinaria, and Madreporaria. 



SUB-SECTION I. 



THE ORDER OF ALCYONARIA. 



This Order contains polyps which have well-developed 

 actinal, mural, and abactinal regions ; eight long, pin- 

 nately-lobed tentacles around a narrow disk ; and which 

 are compound by budding. It comprises three sub-orders, 

 Pennatulacea, Gorgonacea, and Alcyonacea. 



The Sub-Order Pennatulacea, or Sea-Pens, includes 

 polyps which form free, moving communities, and con- 

 tains four families, Pennatulidae, Pavonaridae, Vere- 

 tillidae, and Renillidae. 



RENILLID^E. This Family contains polyps which are 

 arranged symmetrically on the upper surface of a more 



Fig. 507- 



Fig. 508. 



R. Dance, Verrill. 

 Single polyp enlarged 



Renilla, 7?. Dana, Verrill. 



or less flattened disk, to the lower surface of which there 

 is attached a hollow locomotive organ in the form of a 

 peduncle. The Genus Renilla is the principal one. 

 R. reniformis, Cuv., is found on the coast of North and 



