418 ZOOPHYTES. 



G. 1. ISAURA. Simple and not budding. 



G. 2. ZOANTHA. Budding and forming lines of polyps. 



G. 3. PALYTHOA. Budding, and forming incrusting plates or convex 

 masses. 



The species of Palythoa, in which the surface is very prominently 

 mammillate when unexpanded, have been made into a separate genus ; 

 but the transitions from the species in which the union is basal, to 

 those which coalesce by their sides to their very summits, is so gra- 

 dual, that it is deemed preferable to retain all in a single genus. 



GENUS ISAURA. SAVIGNY. 



Zoanthidce non gemmates., simplicissimcB. 

 Non-budding, simple, Zoanthidse. 



The genus Isaura, as instituted by Savigny, comprised also, in part, 

 the budding Zoanthidse. Ehrenberg considers the group identical 

 with the genus Hughea of Lamouroux, and adopts this name, as Sa- 

 vigny's, though of earlier date, had been used for a genus of plants. 

 Ellis's figure (Ellis and Solander, tab. 1, fig. 3), for which Lamour- 

 oux's genus was formed, represents a simple polyp, having a small 

 disk and fifteen to twenty rays, without the radiated margin to the 

 disk that characterizes the Zoanthidse. Its characters are too little 

 known to be received, without farther examination, as the type of the 

 genus. 



Arrangement of the Species. 



1. I. Hemprichii. *3. I. aster. 



2. I. Savignii. *4. I. speciosa. 



1. ISAURA HEMPRICHII. (Ehrenberg.) Dana. 

 I. semipotticaris, nigro-fusca; disci radiis 20-24. 

 Half an inch high, nearly black ; rays of the disk 20 to 24. 



Red Sea, near Tor. Ehrenberg. 

 Hugliea Hemprichii, Ehrenberg, G. x., sp. 1. 



