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XVIII. /On Myostoma, a new genus of the Burmanniacex. 
By JoHN Megs, Esq., F.R.S. & L.S., Commend. Ord. Imp. Bras. Rose. 
(Plate LVII.) 
Read June 7th, 1866. 
Ix April 1847, I communicated to the Linnean Society the account of a new Brazilian 
genus of the Burmanniaceæ, which was published in the Twentieth Volume of the 
Society’s Transactions, under the name of Ophiomeris. I showed that in its more essential 
characters it accorded with the Indian genus Thismia; and in order to include these two 
genera in the family, I proposed to form a third tribe, Thismiee, distinguished from Bur- 
manniee and Dictyostegieæ by having an apterous perianth with a 6-lobed border (each 
alternate lobe being contracted into a long subulate spur), and a succulent capsule 
which opens by a circumscissile line. I have now to describe a third genus of the This- 
miee, which is also of Brazilian origin, its chief peculiarity consisting in the shape and 
condition of the three inner segments of the border of the perianth, which do not open 
in the usual manner, but remain constantly closed, for which reason the name of Myo- 
stoma is given to it*. 
In the regular form of the perianth it resembles Thismia : the tube is not gibbous ; and 
its contracted mouth is in the vertex, not excentrically placed on one side as in Ophio- 
meris. The perianth is succulent, infundibuliform, regularly ventricose towards the 
summit, where it is suddenly contracted into a short eylindrical mouth, which is termi- 
hated by three short erect teeth ; these teeth, or rather claws, belonging to the segments, 
lave the same breadth as their sinuated intervals, and they suddenly become expanded 
into three orbicular very convex segments three times the breadth of the claws, each 
being cordately expanded below into two rounded connivent auricular lobes vie pat 
the claws; these segments, arching over the centre, remain imbricately closed, an 
m entirely conceal the mouth. The other three alternate segments are fleshy, ex- 
tremely narrow, with their margins revolutely coiled back, so that they assume a maa 
form; they are external, as in Thismia, not spirally coiled within the tube in æstiva 
: i ed portion of the tubular 
as in Ophiomeris ; they arise immediately below the contract : : 
mouth, beneath each ts thus unease on a lower level with the m pite 
segments ; they are nearly the length of the tube of the perianth, at first mem 5 cnt 
wntally, then curving downwards. The six equal stamens are, Jd ve app ; th 
"ler, and not united into a broad free annular ring as in 7. OP ait de 
ents, opposite the segments, and pendently attached immediately idelv separated ; 
ed mouth of the perianth, are short, somewhat filamentous, and wide os zm = ; 
each connective is a cuneiform plate, about the length of the filament, wi g 
* From piw, occludo, and grópa, 08. 
Deum Z 38 
