86 welwitsch's African freshwater alg.e. 



presslone mediana ad apicem et intra marginem verruca qiiadii- 

 granulata utrobique, verruca trigranulata intra angulum basalem 

 unumquemque, verruca majori triloba in centro ; a vertice visae 

 rectangulari-oblongae verruca lata emarginata in medio utrobique, 

 aagulis emarginatis, polis unidentatis. Long. 34-5 /x; lat. 27 /a ; 

 lat. apic. 18 /x; lat. isthm. 8 // ; crass. 15 /a. 



Huilla. In paludibus exsiccandis; April 1860. No. 17G. 



This approaches F. divarkatum Lund, (in ]<!oi-a Acta R. Soc. 

 Sclent. Ups. ser. 3, viii. (1871) no. ii. 21, t. ii. f. 5), but differs from 

 it in its broader apex with a very shallow notch, its trilobed median 

 wart, in the two quadrigranulate warts within the apex, and in the 

 trigranulate wart within each basal angle, which latter feature 

 causes the vertical view to be rectangular- oblong. 



10. MiCRASTERIAS Kg. (1827). 



1. M. ARCUATA Bail, in Sniithson. Contrib. ii. Art. 8, 37, t. i, f. G 

 (1851) ; Nordst. iu O/vers. K..Vet.-Akad. Fork. no. 3 (1877), 22-23, 

 li. 1-2. Long. 77 /x ; lat. 90 /x; lat. isthm. 18 /x. 



Huilla. In paludibus exsiccandis ; April 1860. No. 176. 



Var. suBPiNNATiFiDA, var. n. (tab. 366, fig. 7). Var. robustior 

 quam forma tjpica ; lobis lateralibus crassioribus prsesertim ad 

 basin, marginibus superioribus subrectis et horizontalibus, mar- 

 giuibus inferioribus subsigmoideis ; processibus loborum polarum 

 crassioribus et horizontalibus, apicibus leviter retusis in medio. 

 Long. 59-62 ju ; lat. (c. spiu.) 65-68 /x ; lat. isthm. 9-5-13-5 /x. 



Huilla. In paludibus exsiccandis ; April 1860. No. 176. Inter 

 JJtriculariam eralcarataiii, Morro de Lopollo ; April 1860. No. 179. 



This variety appears to connect AI. arcuata with M. pinnatifida ; 

 its lobes are thicker and more horizontal than in typical examples 

 of the former, and the basal ones much resemble those of the latter. 

 The lobes, however, are not so thick and have not the same form 

 as those of M. pmnatijida, the apex of the polar lobe is refuse in 

 the middle, and the lobes all possess that small terminal sharp 

 spine characteristic of all specimens of M. arcuata. 



2. M. TROPICA Nordst. in Vidensk. Medd. Naturh. Foren. Kjohen. 

 1869, no. 14-15, 219, t. ii. f. 15 (1870). il/. eximnsa var. y. Wallich 

 in Ann. Mag. Nat. Hist. ser. 3, v. 276-7, t. xiii. f. 9 (1860). 



Forma. Apical processes almost horizontal ; also with two 

 large granules, one on each side of the extremity of each shius. 

 Long. 136 /x; lat. bas. 116 /x ; lat. apic. 87 /x ; lat. isthm. 20 /x 

 (tab. 366, fig. 1). 



Huilla. In paludibus exsiccandis ; April 1860. No. 176. 



This form has the four larger granules (or papillae) possessed by 

 var. (juianense Eacib. (in Flora (1895), Ixxxi. 34, t. iii. f. 15), but 

 has not the teeth at their apex. 



Var. ELEGANs, var. n. (tab. 366, fig. 2). Var. processibus 

 tenuioribus graciUoribusque marginibus minutius denticulatis, 

 denticulis numerosioribus intra inargines ; membrana delicate 

 punctata. Long. 112 /x ; lat. bas. 103 /a; lat. apic. 56 ju ; lat. 

 isthm. 17 /x. 



