138 CLASS II.— ORDER II. 



HALIMEDA. 



PoLYPiDOMS plant-like and articulated; articula- 

 tions flat or compressed, very rarely cylindrical, g.ene- 

 rally fan-shaped ; axe fibrous ; rind cretaceous, and 

 usually rather thin. 



The Halimedas are unlike any genera of the pre- 

 sent order ; the interior and exterior substances can 

 alone establish their place in it. 



They are found in the seas of the warmer latitudes ; 

 they sometimes, though rarely, appear on the southern 

 shores of the Mediterranean, increasing in number as 

 you approach the equatorial seas. They are abun- 

 dant in the Antilles. 



The Corallinas surpass them in variety and bril- 

 liancy of hues ; although green in the bosom of the 

 sea, they become white on exposure to light and air. 



They rarely exceed a decimetre in height, and 

 are never below five centimetres. 



The Halimedas are sometimes parasites on the 

 Thalassiophytes, but more frequently adhere to 

 rocks or solid sands by numerous fibres of unequal 

 length. 



They are found mixed with the Corallina of Cor- 

 sica, and appear in no wise to alter the anthelminthic 

 and absorbent qualities of that Polypidom. 



NECKLACE-FORMED. 



1. Halimeda monile, Low^er articulations com- 

 pressed, convex, cuneiform, and oblong ; the upper 

 ones nearly cylindrical. 



American seas. 



