in an early stage of growth, traverses the centre of the tube, but which dis- 

 appears on the inflation of the branch. Favellce, lying beneath the peri- 

 pheric layer, are scattered over the branches ; and cruciate tetratipores are 

 dispersed among the filaments of the periphery, on separate individuals. 

 The colour of the frond is a full rosy-red, paler in the tetraspore-bcaring in- 

 dividuals, which are also more succulent than those that produce favellse. 

 The siihstatice is very soft, gelatinous and full when recent ; the frond closely 

 adheres to paper in drying, and shrinks to a mere film. 



This appears to be a rare species. As yet I have only seen 

 two specimens, given me by William Archer, Esq., of Cheshmit, 

 Tasmania; one of them producing /«y<?//<:e, the other tetraspores. 

 The general habit and fructification agree sufficiently with Ha- 

 lymenia, but the structure of the periphery is rather more com- 

 plex. Still, there is nothing so discordant as to force us to 

 construct a genus for our present plant. Externally there is a 

 striking resemblance to two Algae of very difierent structure and 

 affinities, namely, our Bindera splacUnoides (Plate CXI.), and the 

 Chrppnenia Enteromorpha of the Keys of Florida. These three 

 have the same colour, substance, and ramification, so much so, 

 that, structure and fruit apart, they could with difficulty be dis- 

 tinguished : affording another evidence of the necessity of exa- 

 mining the intimate structure of Algae, before deciding on their 

 affinities. 



Fig. 1. Halymenia saccata, — the no.tural size. 2. Portion of the periphery, 

 with imbedded tetraspores. 3. A tetraspore. 4. Portion of periphery, 

 with an immersed /aye/Za.- — variously magnified. 



