found at Port Natal, South Africa, but which is now known to 

 exist in Western Australia, and is particularly abundant in rock- 

 pools at Newcastle, New South Wales. An earlier manuscript 

 generic name, Hemitrema, was given it by Dr. R. Brown, but not 

 having been duly published, it has yielded to that here adopted. 

 A second species of the genus was collected by me at Ceylon ; 

 and subsequently I added two more from the Australian coast, 

 and one from the shores of the Friendly Islands. Thus we 

 are acquainted with five species of this curious genus, which 

 ranges through a moietv at least of the Indian and Pacific 

 Oceans. 



The subject of our Plate was first found by me in January, 

 1854, at King George's Sound, and supposing it to be the only 

 Australian type of the genus, I named it M. australis. Much 

 finer specimens, from one of which our drawing is taken, have 

 since been received from Mr. Clifton, but as yet I have seen 

 none in which the frond is not much lacerated. Fragments of 

 very large size of what must either be this species or a new one, 

 have been picked up at Georgetown, Tasmania, both by Mr. 

 Gunn and the Rev. J. Fereday, but not in a sufficiently perfect 

 state (wanting the base of the frond) to enable us to recog- 

 nize them specifically. 



M. australis is chiefly to be known from M. elegans by the 

 cartilaginous stipes and thicker base of the frond. It is a larger 

 and more luxuriant species, and has a broader fringe. 



In a young state the several species of this genus are not to 

 be distinguished by any character, either of structure or habit, 

 from Nitophylla, and yet their fruit is formed on so different a 

 type that they cannot be placed in the same family. 



Fig. 1. Maktensia australis, — the natural size. 2. Small portion of the net- 

 work, showing the toothed margin, and the areolation of the surface. 3. 

 Some bars of the net, containing tetraspores. 4. Tetraspores : — the latter 

 figures variously magnified. 



