A Revision of the Genus Aulacodiscus Ehrb. By J. Rattray. 381 



Processes small or minute 19 



19. Markings quadrate, pearly, concentric on elevated area . . . . neglectus. 



„ non-concentric 20 



20. Markings rounded with brown central dot, rows on compart- 



ments parallel pulcher. 



„ rounded in wide rows with hyaline interspaces, 



towards centre polygonal dispersus. 



„ angular, rows parallel, primary rays with rows 



diverging widely at outer ends umbonatus. 



„ polygonal, not pearly, processes with proximal 



portion smaller than distal, primary rays diverging 



but slightly lucidus. 



„ pologonal, not pearly, processes placed near the 



semiradius with large clear space at their base, 



central space indistinct coronatus. 



„ in radial rows or irregular 21 



21. Markings on elevated portion large, round, irregularly placed, 



outside of this much smaller and radial ; pro- 

 cesses with wide shallow constriction probabilis. 



„ more equal; primary rays distinct 22 



22. Markings round, interspaces hyaline ; processes with sharp 



median constriction simplex. 



„ polygonal, without interspaces 23 



23. Markings small (6 in - 01 mm.); primary rays cruciform; 



processes with free ends protuberant concinnus. 



Markings larger (4 in 0*01 mm.); processes clavate, free ends 



simply rounded radiosus. 



Markings still larger (2 to 3 in 0" 01 mm.); processes with 



sharp median constriction, and no clear space at their base cellulosus. 

 18. Inflations wide, cuneate, sides convex, inner ends sharply 



circumscribed formosus. 



Inflations with inner ends merging into raised central area . . 24 



24. Inflations rising gently on inner portion, steeply near processes mammosus. 



„ more uniform.. 25 



25. Rows parallel on compartments, valves transparent . . . . gracilis. 



„ radial 26 



26. Primary rays on a level with central area, cruciform, more 



conspicuous than rest of valve, sides of inflations indistinct quadrans. 



Primary rays rising slightly outwards 27 



27. Inflations long, sides convex, more conspicuous in outer portion 



where the oblique markings are distinct Janischii. 



Inflations with sides more straight, the oblique markings less 



obvious 28 



28. Markings rounded, processes narrow, cylindrical inflatus. 



„ polygonal, processes with a constriction 29 



29. Non-apiculate carruthersianus. 



Apiculate 30 



30. Outer ends of inflations sharply denned 31 



„ „ merging gradually into peripheral area 32 



31 . Proximal portion of processes larger than distal, markings sub- 



pearly, protuberances on border large ductus. 



Proximal portion of processes much smaller than distal, 



markings more delicate Petersii. 



32. A distinctly defined broad apiculate zone at border, apiculi on 



inflations small macraeanus. 



No such zone, apiculi on inflations large aucMandicus. 



„ „ „ „ few, minute Wittii. 



9. Non-crateriform 33 



Crateriform 34 



33. A prominent deeply serrated ridge on zone of, and between 



processes Lahuseni. 



No such ridge 35 



35. A large, distinctly defined, elliptical or triangular, finely 



areolate central area 36 



No such area 37 



