ALGiE FROM CENTRAL AFRICA. 879 14. CosMARiuM PECTiNoiDES WoUg, Desm. U. S. 88, pi. xiv. figs. 12-13. Long. 57 /a; lat. 43 /x; lat. isthm. 15 /x; crass. 27 /a (Fig. 9). Mwangadan Eiver, S. of Fuladoga. The nearest species to this is C. binum Nordst. in Wittr. & Nordst. Alg. Exsicc. 1880, no. 383, which differs chiefly in its linear sinus, its rectangular basal angles, and its truncate apex. The close resemblance between these two species seems to have escaped the notice of some previous observers who have had occasion to refer to C. binum. 15. C. Mwangadanense, nov. sp. (Fig. 11). C. submediocre, li-plo longius quam latum, profunde constrictum, sinu linear! extremo subampliato ; semicellulae subsemicirculares cum apicibus truncatis, angulis basalibus rotundatis, lateribus leviter biundulatis, elevationibus granulatis, granulis intra marginem subter elevationi- bus, in centro cum tumore magno granulorum majorum ; a vertice visas latae ellipticae, cum tumore ad medio utrobique. Long. 49 /x ; lat. 41 fx; lat. isthm. 11-5 /x. Mwangadan Eiver, S. of Fuladoga. The isolated patches of granules of this species are very charac- teristic. 16. C. suBcosTATUM Nordst. in Wittr. & Nordst. Alg. et (Edog. in Ital. et Tyrol. 37, taf. xii. fig. 13. Forma minor (Fig. 15). Forma minor, crenis lateralibus pauci- oribus. Long. 21-5-23 /x; lat. 18-19 /x; lat. isthm. 4-2-4-8 /x; crass. 11-5 /x. Mwangadan River, S. of Fuladoga. 17. C. Blyttii Wille, Bidrag til Kundsk. om Norges Ferskv. Alg. 25, tab. i. fig. 7. Long. 21 fi ; lat. 19 fx ; lat. isthm. 6 /x. G. Las- chan, Leikipia. 18. 0. PUNCTULATUM Brcb. var. ornatum Istv. Schaar. Diag. Algar. Nov., Notarisia, 1886, 237. Forma cum granulis radiatim dis- positis. Long. 21 /x ; lat. 18 /x ; lat. isthm. 6 /x. Mwangadan River, S. of Fuladoga. 19. C. Phaseolus Br^b. ; Ralfs, Brit. Desm. 106, tab. 32, fig. 5. Long. 27 /x ; lat. 26 /x ; lat. isthm. 7*5 /x ; crass. 14-5 /x. Mwanga- dan River, S. of Fuladoga. 20. C. trochiscum, nov. sp. (Fig. 12). C. parvum, IJ-plo longius quam latum, profundissime constrictum, sinu angusto- lineari extremo ampliato ; semicellulaB oblongo-rectangulares, an- gulis leviter rotundatis, angulis superioribus subincrassatis ; a vertice visaB ellipticsB, tumoribus parvis binis ad medium utrobique ; membrana glabra. Long. 22-5 /x; lat. 21 /x; lat. isthm. 4*5 /x; crass. 13 /x. Mwangadan River, S. of Fuladoga. 21. C. RECTANGULARE Grun. in Rabh. Fl. Europ. Alg. iii. 166. C. gotlandicum Wittr. Om Gott. och OL Sotv. Alg, 60, t. iv. fig. 14. Var. AFRioANUM, n. var. (Fig. 14). Var. semicellulis multe alti- oribus, lateribus inferioribus divergentibus, lateribus superioribus longioribus, apicibus angustioribus, isthmo angustiori. Long. 31-35 /x; lat. 24-25 /x; lat. isthm. 6-7*5 /x; crass. 15 /x. Mwanga- dan River, S. of Fuladoga. It differs from C. rectangulare Grun. var. Cambrense (Turn.) 3 2
