TRIBE II. CARYOPHYLLACEA. 423 



The Palythose form incrusting plates or convex masses. When 

 the polyps are united by their bases only, the plates are thin, and the 

 polyps when contracted form rounded or cylindrical prominences over 

 the surface ; but as the union becomes more general, and they coa- 

 lesce by their sides above as well as at base, the plates are thicker and 

 the polyps less prominent ; and when the coalescence extends quite 

 to their summits, the unexpanded zoophytes are convex, with nearly 

 a flat surface. 



The genus Palythoa was separated from Zoantha by Lamouroux. 

 Lesueur subsequently subdividing the Zoantb.83, instituted the two 

 genera Mammittifera and Corticifera, the first including the Palythoa?, 

 with mammilliform prominences when contracted ; and the second, 

 those in which these prominences are obsolete or nearly so. Schweig- 

 ger's genus Cavolinia, and Oken's Tethya, fall into this group. 



Arrangement of the Species. 



I. Polyps united only at base, forming when contracted very prominent mammilla; 

 over the surface. 



1. P. denudata. 3. P. nymphcea. 



2. P. auricula. 4. P. fuliginosa. 



II. Polyps united nearly to their summits ; surface of the contracted zoophyte mam- 

 millate. 



5. P. mammillosa. 6. P. ocellata. 



III. Polyps united quite to their summits; surface of the zoophyte scarcely at all 

 mammillate. 



7. P. glareola. 9. P. argus. 



8. P. flavo-viridis. *10. P. csesia. 



I. Palythoce basi tantum coadunake. 



1. PALYTHOA DENUDATA. (Cavotini.} Dana. 



P. purpurea, polypis basi tantum coadunatis, valde prominentibus, cylin- 

 dricis et davatis ; 1-2'" crassis et 6-9'" longis ; tentaculis triseriatis, 

 serie extimd minore. 



Purple ; the polyps united only at base, very prominent, cylindri- 

 cal, and clavate, 1 to 2 lines thick, and 6 to 9 high ; tentacles in 

 three series, the outer smallest. 



