BRITISH DESMIDIE^. 203 



33. End view with broad, emarginate or bifid lobes enorme. 



End view with the angles either rounded or tapering into lobes . . 34 



34. Spines scarcely distinguishable from the associated granules . . asperum. 

 Spines distinct 35 



35. End \-iew vsith convex sides and rounded angles, and fringed 



with stout forked spines spongiosum. 



End Adew with concave sides ; angles not rounded 36 



36. Each angle in end view terminated by a spine with two 



accessory spines spinosum. 



Each angle in end view tapering into a process tipped by 



three or four acute points or spines 37 



37. Each side in end view with two slender forked spines, with 



or without other spines ; rays slender vestitum. 



End view without slender forked spines at the sides ; rays short, stout. 38 



38. Rays curved in end view contr over sum. 



Rays straight in end view aculeatum. 



12. DiDYMOCLADON. 



., furcigerus. 



13. Tetmemorus. 



1 . Frond fusiform in the front view ; puncta distmct, scattered, granulatus. 

 Frond not fusiform in the front view ; piuicta either very in- 

 distinct or in longitudinal rows 2 



2. Puncta distinct, in longitudinal rows Brebissonii. 



Puncta either wanting or indistinct and scattered Icevis. 



14. Penium, 



1 . Frond granulate or striate 2 



Frond smooth 3 



2. Granules arranged in longitudinal rows margaritaceum. 



Granules scattered CyUndrus. 



3. Endochrome transversely divided into four portions .... interruptum. 

 Eudochrome not divided into more than two portions 4 



4. Frond lanceolate, fusiform or elliptic 5 



Frond cylindrical 6 



5. Frond elliptic ; fillets undulating Digitus. 



Frond lanceolate or fusiform ; fillets straight dosterioides. 



6. Ends truncate truncatum. 



Ends rounded 7 



