380 Transactions of the Society. 



Artificial Key. 



1. Outline polygonal polygonum. 



„ circular 2 



2. Processes absent 3 



„ present 4 



S. Primary rays indistinct, markings round, interspaces hyaliuo suspectus. 



„ „ distinct, markings polygonal, in contact .. .. apedicellatus. 



4. A prominent broad crescentic band on peripheral side of 



processes Kiltoni. 



No sueb band 5 



5. Surface Hat to border (J 



„ „ to zone of processes 7 



„ „ from centre for a portion of radius within zone 



of processes, centre not depressed 8 



„ depressed at centre 9 



6. A hyaline band at outer edge of central space with short 



extensions into apices of compartments ; markings unre- 

 solved ex/gnus. 



No such band ; markings polygonal, minute but larger, clear 



area at base of processes large barbadensis. 



7. Reticulum coarse, meshes radial, primary rays undifferenti- 



ated; opaque Argus. 



Meshes within processes large, rounded, outermost band much 

 larger than the others, with division lines radial. Markings 

 more distinct, frequently oval and oblique Thumii. 



No reticulum 10 



10. Apiculate ; primary rays distinct ; processes hourglass- 



shaped, clear space at their base minute scaber. 



Non-apiculate 11 



11. A dark band at zone of processes more sharply defined on 



inner than on outer side; primary rays distinct ; processes 

 small, subcylindrical, clear space at their base absent .. .. Sturlii. 

 No such band 12 



12. Markings concentric Browneii. 



„ non-concentric 13 



13. Markings rounded with punctate interspaces 14 



„ round, granular, interspaces hyaline ; central space 

 absent; striated border wide; processes nu- 

 merous (14) minutus. 



„ polygonal, without interspaces 15 



14. Processes large, faint space at base punctate ; lurid Comberi. 



„ with space at base semicircular, hyaline ; valve 

 transparent, edge of central area somewhat con- 

 cave between processes hyalinus. 



„ minute, space at their base absent Beeveriae. 



15. Processes minute, subclavate, clear space at their base absent .. elegans. 



„ larger, subcylindrical, free ends truncate, space at 



their base small compactus. 



„ large, with median constriction, and free ends 



rounded; border hyaline parvulus. 



„ small, constriction wide, median, clear space at their 

 base small, outline of central portion of valve 

 concave outwards between processes prominens. 



8. A basin-like deep depression at middle of compartments . . .. excuvatus. 

 Depression wide, shallow ; markings in interrupted rows 



arranged in radial fasciculate patches with wide irregular 

 hyaline radial interspaces anitus. 



A clear angular zone a short distance within processes .. .. patens. 



No such depression or clear zone 10 



16. Without large cuneate inflations 17 



Such inflations present 18 



17. Processes large, proximal portion much smaller than distal, 



inserted far in on valve, clear space at their base large, border 



strias punctate Rattrayii. 



