250 DESCRIPTION OF {^Polygastrica. 



neck broad. End \'icw bilobed. Empty frond punctate. Sporangia 

 orbicular, with subulate spines. Length 1-1 85th. 



ExJASTKTJM ansatum (Ehr.) — Segments inflated at the base, and 

 tapering upwards to the notched but not dilated extremity ; trans- 

 verse view cruciform. The end view has two circular and entire 

 lobes. Empty frond punctate. Length l-315th. 



E. circulare. — Segments three-lobed, mostly with five basal 

 tubercles ; four of them usually disposed semi-cu'cularly about the 

 fifth; end notched, scarcely dilated. Length 1- 320th. 



E. pectinatum. — Segments three-lobed; terminal lobe dilated, 

 scarcely emarginate ; lateral lobes emarginate, horizontal ; end view 

 two-lobed at each end, and two lobules on each side. Neck short 

 and broad. (P. 13. f. 10.) Empty frond pimctate. It differs 

 from aU the preceding, m the absence of a terminal notch, in the 

 lobules of the end lobe, and in having the ends emarginate in the 

 transverse view. Sporangia orbicular mth conical tubercles, or 

 short obtuse spines. (P. 13. f. 30.) Length l-362nd. Boggy pools. 



E. gemmatum may be known from all in this section, except E. 

 pectinatum, by the absence of a linear terminal notch ; and from that 

 species by the smallness of the end lobe, and the outward direction of 

 its angles, and by the miuute granulation of the projecting parts. 

 Length 1 -442nd. 



3. Frond without a distinct terminal lohe, and frequently having a 

 processor an acute angle at the corners of the terminal portion. 



E. rostratum, minute, oblong; ends protuberant, emarginate, and 

 angular, with a horizontal spiue on each side ; neck, attaching the 

 terminal lobe of each segment, short and broad. The angular and 

 less prominent ends distinguish it from E. elegans. Sporangia 

 spinous. Length 1 -649th to 1 -508th. 



E. elegans, very miuute, oblong ; ends emarginate, pouting and 

 rounded. 



Var. fa. J — Segments slightly constricted beneath the end lobe, 

 which has on each side a short horizontal spine. 



Var. fhj itierme ; segments sinuatcd rather than lobed, and without 

 spines. 



Var. fc.J — Segments as in fh), but with two or more spines, 

 directed obliquely outwards. Length l-421st to l-884th. 



E. hinale. — Segments concave, or truncate at the end ; not pro- 



