eC 2p nye be ee 
Evans: HEpATICAE OF PuERTO RIco 223 
haps the most striking peculiarities of the species, aside from these 
wings and the short but distinct beak of the perianth, are the small 
and deeply bifid underleaves, which are usually unidentate on the 
sides, and the narrow bracteoles, which are destitute of marginal 
denticulations, 
Among the other Puerto Rico species of Prionolejeunea, P. 
innovata and P. aemula bear some resemblance to the species just 
described. In P. cxnovata, however, the underleaves are larger 
and less deeply bifid, the female branch bears a subfloral innova- 
tion, the bracteole is broader and is crenulate or denticulate on the 
margin, the perianth is less deeply emarginate and the apical beak 
is obsolete. In F. aemula the lobes of the leaves are much more 
abruptly dilated, the margins are more regularly denticulate, the 
underleaves have blunter divisions and are usually crenulate on 
their margins, the bracteole is distinctly denticulate, the beak of the 
perianth is obsolete, and the wings are less conspicuously toothed. 
Prionolejeunea exauriculata sp. nov. 
_ Dull yellowish green, becoming brownish upon drying, grow- 
ing in depressed and intricate mats: stems 0.09 mm. in diameter, 
‘Prostrate, sparingly branched, the branches widely spreading : 
leaves contiguous or loosely imbricated, the lobe obliquely 
Spreading, plane or slightly convex, sometimes reflexed at the 
apex, somewhat falcate, 0.5 mm. long, 0.4 mm. wide, outer part 
, acute to rounded sinus, margin entire 
°r vaguely crenulate from projecting cells, rarely unidentate on the 
