204 DTJBLIN NATTTEAL HiaiORT SOCIETY. 



lobes ; ends straight, or convex, or having at the middle of the rounded 

 ends a very slight concavity. 



General Generic Description: The fronds are simple, as long as 

 or longer than broad, compressed, without inflations, deeply divided 

 into two segments by a constriction, forming a broad acute-angled notch ; 

 each segment constiicted by a broad notch or sinuosity upon each side 

 into two subdivisions fonning three lobes, the basal lobes broadest within 

 and attenuated outwards, not radial, but extending horizontally and 

 parallel in their direction with those of the opposite segment ; the end- 

 lobe expanded laterally into two attenuated projections, which are hori- 

 zontally disposed and parallel in their direction with that of basal lobes, 

 so that the entire frond is of a pinnatifid character ; the ends of the 

 fronds convex, straight, or having at the middle a very slight concavity 

 or depression, not emarginate. 



Tetrachastrum mucronatum (sp. nov.). 



Specific Characters : Frond longer than broad ; ends rounded, hav- 

 ing a slight centrtd concavity ; end lobe having its lateral projections 

 terminated by a mucro; basal lobes broadly and bluntly triangular, 

 having at their margin at each side either one, two, or three minute 

 mucro-like spines ; empty frond punctate, the puncta scattered. 



Symbol : al, c^ parallel {vide supra). 



Locality : Bog near Carrickmore, Co. Tyrone. 



Measurement : Length of frond, y^y ; greatest width, g^j ; width 

 of neck, 373-; diameter at constriction, ^^q ' gi'^^^^st depth, -^^ of an 

 inch. 



Plate I. — Fig. 5, front view with endochrome ; Fig. 6, empty frond ; 

 Fig. 7, outline of side view ; Fig. 8, outline of transverse view. 



General Description: The frond in this species is large, smooth, 

 entire, about one-fourth longer than broad ; in the front-view divided 

 into two segments by a deep constriction forming an acute-angled, 

 straight- sided notch, not linear, but broadest at the outside. The seg- 

 ments are constricted about two-thirds of the way from the base by a 

 rounded sinuosity, causing the basal lobes to be of a bluntly triangular 

 outline, straight on the lower, turgid or convex on the upper margin, 

 and furnished thereon with one, two, or three minute mucro-like spines, 

 one always at each basal angle. The basal lobes slope upwards to form 

 a broad neck, uniting the terminal lobe to the basal portion : supposing 

 the end to be absent , the frond would be orbicular. The lateral projec- 

 tions of the end-lobe have their extremities tipped by a mucro, and 

 somewhat proj ected downwards. Ends of the fronds convex with a gentle 

 central concavity. In the side-view the frond is smooth, about four 

 times longer than its greatest depth ; the central constriction is rather 

 deep ; the segments in this view ovate, turgid near the constriction, 

 somewhat tapered towards the ends, which are rounded. The transverse 

 view is broadly fusiform ; the endochrome rich green, with scattered 

 granules. The empty frond is punctate, the puncta scattered. 



