G. MELOBESIA. 141 



of America ; from liieir rarity in collections, it is pro- 

 bable they arc not very numerous. 



FAN.SHAPED. 



1. Udotea flabellata. Stem simple, with a fibrous 

 root ; expansions divided in fan-shaped branches, 

 which are r&,rely proliferous. Plate 12. fig. 1. 



Equatorial seas of America. 



CONGLUTINATED. 



2. Udotea conglutinata. Stem simple, with a fibrous 

 root ; expansion plain, and fan-shaped. 



Coasts of the Bahamas. 



MELOBESIA. 



Stony Polypidom, found in thin patches of greater 

 or less expansion on the surface of the Thalassio- 

 phytes ; cells very small, and placed at the summit 

 of small tubercles dispersed upon the patches. 



The Melobesias form patches of various sizes, 

 sometimes round and regular, and at others irre- 

 gular ; some wholly cover the marine plants with a 

 calcareous layer, so as entirely to conceal their 

 form and colour ; whilst others merely appear like 

 powder or mouldiness on the surface of the plants, 

 according to the size of the patches, which resemble 

 small scales or atoms of dust. On these patches 

 may be discerned projecting tubercles, having in their 

 centre a small hole, or cell, which serves as a dwell- 



