G. ISIS. 233 



Their height varies from one to four decimetres. 

 They originate in the Indian and Australasian seas. 



VERTICILLATED. 



1. MopSRA verticillata. Branches pinnated ; twigs 

 simple, and long ; polypi recurved like a hook. — 

 Plate 18. fig. 2. 



Australasia. 



DICHOTOMOUS. 



2. Mo PS E A dkhotoma. Branches slender, cylin- 

 drical, almost filiform, and dichotomous at each arti- 

 culation ; polypi mammiform in the higher branches, 

 tuberculous in the middle ones, and superficial in the 

 lower; rind smooth upon the stem. 



Indian Ocean. 



ISIS. 



A TREE-FORMED Polypidom; rind very thick, 

 friable, not adhering to the axe, from which it easily 

 detaches ; cells dispersed and superficial. 



The Isideas, like all the corticiferous Polypidoms, 

 are composed of two parts, one central, called the axe, 

 and an envelope of a fleshy consistency, called the 

 rind, as in the Gorgonias. In this genus, however, 

 the articulations which mark the order are alter- 

 nately stony and horny, varying in their height and 

 their diameter : the first are white, slightly trans- 

 lucent, marked with longitudinal furrow^s of greater 

 or less depth, sometimes larger and frequently 



Cor. 2 G 



