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 tooth-like rostratum. 



End projections pouting and rounded eleyans. 



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 vpith straight or concave sides ; neck very 



long insigne. 



Transverse \ievF with inflated or lobed middle 9 



9. Segments distinctly 5-lobed pinnatnm. 



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 ampuUaceum. 



Segments pyramidal, not inflated affine. 



12. End margin truncate, with acute angles hinale. 



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 jomed to the basal portion by a neck. 16 

 Margins sinuated but not lobed suhlobatum. 



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 lialfsii. 



Frond not lenticular 4 



