MADREPORES. 



1 75 



ordinary height, becoming contracted about the middle, like an hour- 

 glass. When the creature is fully expanded, the tentacula become 

 distended and elongated to about the length of the transverse 

 diameter of the body ; and they are generally darker at their ex- 

 tremities than towards the base. The present species possesses a 

 power of considerably altering its shape ; sometimes the mouth is 

 depressed, and at others it is elevated into an obtuse cone. " This is 

 one of the most inactive of its order," says Mr. A. Couch ; " for, 

 whether in a state of contraction or expansion, it will remain so for 



Fig. 59. Zoanthus socialis 



), magnified. 



many days without apparent change. In its expanded state a touch 

 will make it contract, and it will commonly remain so for many 

 days." The trailing connecting-band is flat, thin, narrow, glandular, 

 and of the same texture as the polyp, sometimes enlarging into 

 small papillary eminences, which, as they become enlarged, become 

 developed into polyps. 



The genus Caryophillia (Lamarck), from /captW, a nut, and $\>\\ov, a 

 leaf, has the polypidom permanently fixed, simple, striated longitudi- 

 nally, and the summit hollowed into a lamellated star-like cup ; the 

 animal, actinia-like, is provided with a simple or double crown of ten- 

 tacula, projecting from the surface of star-like, cylindrical, cone-shaped 



