fastigiate, many times dichotonious, with luirrow, but rounded axils, and 

 erect or suberect laciiiife. Lacinise linear, 1^-2 lines wide, truncate or emar- 

 giuate, slightly tliickened at the margin, and more or less concave or sub- 

 canaliculate on one side. Cijstocarps very convex, constricted at base, se- 

 veral clustered round the apex, as large as poppy-seed, dark-red, with a very 

 thick pericarp and densely compacted nucleus. Tdraspores lodged in shield- 

 like, llat nemathecia, placed immediately under the slightly dilated apices, 

 cruciate, vertical. Substance of the frond rather rigid and thick ; central 

 cellules large and in few rows. The colour is a full and rather dark red, be- 

 coming brownish in drying. The frond shrinks in drying, and imperfectly 

 adheres to paper. 



This species is placed by J. Agardh in Acropeltis, of which it 

 certainly has the tetrasporic fruit ; but the structure of frond, and 

 general habit, are those of Rhodpnenia. The cystocarpic fruit 

 of AcropeUis being unknown, it is premature to say whether it 

 has good claims to be kept up as a genus or not. But for the 

 nature of its medullary layer, there seems nothing to prevent its 

 being referred to Rhodpnenia. 



The present species is very common at Rottnest Island, but 

 has not yet been found on other parts of the Australian coasts. 

 Another species, erroneously referred by me to R. corallina, and 

 which seems very near R. Pcdwdta, is abundant in several 

 places, from one end of the Australian continent to the other. 



Fig. 1, Ehodymbnia australis, — the natural she. 2. Apices, bearing cysto- 

 carps. 3. Vertical section of a cystocarp. 4. Apices, bearing nematliecia. 

 5. Cross section of lamina and «e/;/a/Z!eatfw,. 6. A tetraspore. 7. Longi- 

 tudinal section of lamina ; the latter figures variously inar/nifed. 



