214 ACTINOZOi. 



Family 3. Pennatulid^. 



Corallum sclerobasic, tissue secretions also 

 being sometimes present. Coenosarc free. 



Family 4. Gtokgonid^. 



Corallum sclerobasic, sulcate, with or with- 

 out additional tissue secretions. Coenosarc 

 shrub-like, attached by its expanded proximal 

 extremity. 



4. Order 3 : Rugaisa. — Among the Rugosa 

 a highly developed sclerodermic skeleton occurs, 

 each corallite beiug very distinct, and presenting, 

 in many cases, both septa and tabulae. Some 

 Rugosa are simple, the corallite often attaining a 

 considerable size ; others are composite, increasing 

 either by lateral or calicular gemmation, these 

 two processes, but especially the latter, checking 

 to a greater or less extent the growth of the 

 primitive corallite. A true coenenchyma is ab- 

 sent. 



In Stauria, Holocystis, and Polycoelia four of 

 the septa admit readily of being distinguished, 

 by their greater development, from the others, but 

 in Cyathaxonia only one primary septum or 

 chamber remains conspicuous. So, also, of Za- 

 phrentis and its more immediate allies {jig. 38). 

 In other genera the septa radiate, in about an 

 equal manner, from the inner surface of the theca. 

 In many Rugosa they are incomplete, that is, 

 " do not extend from the bottom to the top of the 

 corallite, in the form of uninterrupted laminae." 



The tabulse exhibit various grades of develop- 

 ment, and, in some species, are wanting altogether. 



In a few Rugosa the columella is cylindrical, 

 and of large size ; in others, styliform or lamellar : 



