150 ZOOPHYTOLOGY. 
2. Menipea, Lamx. 
Cells oblong, abbreviated, or elongated and attenuated downwards ; im- 
perforate behind with a sessile lateral avicularium (frequently absent), and 
with one or two sessile avicularia (also frequently absent) on the front of 
the cell. Ovicell globular, immersed in the internode. 
This genus requires careful revision. It is said to be 
distinguished from Emma (Gray) by the structure of the 
cell-mouth, which is subtriangular in the latter genus, the 
opening being partially filled up by a tubercular calcareous 
plate ; and by the position of the lateral avicularium, which 
in Emma is entirely below the cell-aperture; while in Me- 
nipea it is seated, when present, on the upper and outer angle 
of the cell. 
The two new species are so completely intermediate that I 
believe I am justified in unitnmg the Emme with the true 
Menipez into what I conceive to be a most natural generic 
group. MM. ternata (Ellis) may be taken as a type of the 
genus thus constituted. MM. Fuegensis (Busk) approaches it 
closely. The avicularia are still at the upper angle of the 
cell, and the cell-lip is still simple. The operculum, however, 
is reduced to a curved spine. In M. Buskii the lip is more 
projecting, and the calcareous plate which partially covers 
the cell-mouth is tuberculated. The lateral avicularium is 
slightly depressed, though still opposite the upper third of 
the aperture. The opercular spine is again expanded. 
M. tricellota closely resembles the last in habit, but the 
tuberculated plate round the mouth is still more fully deve- 
loped, the lip is more elevated, and the much smaller lateral 
avicularium is below the cell-mouth. The operculum is 
again reduced to a rudimentary spine. 
M. cyathus is binate, the cell-mouth large and simple, as 
in M. ternata; the lateral avicularium very large half way 
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, MW. cirrata 
(Lamx.), 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 aperture, 
the lower part calcareous and fixed, the upper portion a 
movable, crescentic, horny operculum, closing over the true 
