88 DUBLIN UNIVERSITY 



M. tricellata closely resembles the last in habit, but the tuberculated 

 plate round the mouth is still more fully developed, the lip is more ele- 

 vated, and the much smaller lateral avicularium is below the cell-mouth. 

 The operculum is again reduced to a rudimentary spine. 



M. cyathm is binate, the cell-mouth large and simple, as in M. ter- 

 nata ; the lateral avicularium very large halfway down the cell-mouth. 

 The operculum once more expanded and branched. It almost requires 

 a microscope to distinguish M. crystallina ( Gray) from the last, they are 

 so similar in habit and general appearance ; but in M. crystallina the 

 expanded operculum is again absent, the lateral avicularia are reduced 

 in size, and seated near the base of the cell, and the cell-mouth is again 

 contracted by a granular calcareous plate. 



The right of this genus to the name of Menipea depends upon the 

 retention in it of the six-celled species, Jf. cirrata(Zamx.), of the propriety 

 of which I think there can be little doubt. The general character is still 

 remarkably the same. In M. cirrata a smooth plate covers the cell aper- 

 ture, the lower part calcareous and fixed, the upper portion a movable, 

 crescentic, horny operculum, closing over the true opening. I have not 

 seen M. Patagonica {Bush), and from the figure I am more doubtful as 

 to its position. All the species are distinguished by the presence of one 

 or more sessile avicularia on the front of the cells, and by the remarkable 

 hollow curved spines attached round the upper lip of the cell-mouth by 

 horny joints. 



This group does not seem to " fruit" freely. I do not know the ovi- 

 cell even in our common British species, M. ternata {Ellis) ; but fortu- 

 nately Dr. Harvey's collection contains a branch of M. Buskii from 

 Bass's Strait, bearing several : globular, the surface granulated, im- 

 mersed among the cells in the middle of the internode. One can scarcely 

 doubt that all these closely allied forms have similar reproductive organs, 

 and, if so, the ovicells will give an excellent generic character. 



M. triseriata (Busk) and M. multiseriata (Busk), which have their 

 ovicells galeate and superior, like those of Scrupocellaria, must seek other 

 congeners. 



I do not consider it necessary to subdivide the genus. 



1. — M. cyathus, n. 8. Plate IX., Figs. 1, 1* 



Cells very short and round; two in each internode, one a little 

 above the other cell-mouth ; large, oval, oblique ; rim slightly thickened, 



