198 BRITISH DESMIDIE^. 



5. Ends protuberant or pouting ; angles usually terminated by 



a spine 6 



End straight or convex 7 



6. End projections angular and tootb-like rostratum. 



End projections pouting and rounded elegans. 



7. End lobe distinct, dilated, and connected to the basal por- 



tion by a distinct neck 8 



End lobe obscure, not dilated 12 



8. Transverse view with straight or concave sides ; neck very 



long insigne. 



Transverse view with inflated or lobed middle 9 



9. Segments distinctly 5-lobed pinnatum. 



Segments not 5-lobed 10 



10. Neck of segments included between the process-like elon- 



gations of middle lobes , humerosum. 



Neck exserted 11 



1 1 . Segments inflated at the base ampullaceum. 



Segments pyramidal, not inflated affine. 



1 2. End margin truncate, with acute angles binale. 



Ends rounded 13 



13. Segments cuneiform, not lobed cuneatum. 



Segments either lobed or contracted upwards into a neck 



(not cuneiform) 14 



14. Transverse view with one protuberance on each side ansatum. 



Transverse view with three protuberances on each side circulare. 



Transverse view with four protuberances on each side Didelta. 



15. End lobe distinct, dilated and joined to the basal portion by a neck. 16 

 Margins sinuated but not lobed sublobatum. 



16. Protuberances smooth ; end margin straight pectinatum. 



Protuberances granulated ; end margin concave gemmatum. 



8. COSMARIUM. 



1 . Constriction forming a linear notch on each side ; end view 



not circular 2 



Constriction not forming notches at the sides ; end view circular. . 24 



2. Segments smooth, entire 3 



Segments crenate or margined by pearly granules 9 



3. Frond lenticular JRalfsii. 



Frond not lenticular 4 



