BY G. 1. PLAYFAIK. 535 



Long. 56-75; lat. 14-16 /x. 



Syn., Nav. Hitchcockii Ehr., cf. Donkin, Br. Diats., PI. v., f.4, 

 whose figure works out at long. 70 jx. Closely connected is K. 

 incurva Greg., (Donkin, I.e., PI. vi., f.2, and O'Meara, Irish Diats., 

 PI. 31, f.56) All the Crassinerves-group of the genus Navicida 

 should be united with Vanheu7-ckia, the inci'assate columella 

 (whether simple or divided) being characteristic; and I am de- 

 cidedly of opinion that they are all immature forms of Stauroneis. 

 Here they are always found in company with varieties of that 

 genus. 



Genus Stenopierobia Breb. 

 Sten. ANCEPs(Lewis) Hreb. (PL Ivi., f.l9). 

 Long. 133-168; lat. 8-9 ja. 



Not Sten. anceps Heribaud, Diats. d'Auvergne, PI. v., f.4. The 

 form given by Lewis, Proc. Acad. Nat. Sci. Philad. 1864, is 

 identical \y\th. Nitzschia frmiconica Reinsch, Mittelfr., Pl.i., f.la, 

 but lacks the alse in side-view. The dimensions of our specimens 

 tally exactly with those of Reinsch. 



Var. iNTKi<MEDiA( Lewis) mihi. (PL Ivi., f.20). 



Long. 250; lat. centr. 10, subsp. 8; crass. 12 /x. 



This is, as far as my observations go, the full-grown form of 

 the species. It narrows gradually from the centre to the ends, 

 which are slightly dilated. I have ntjt noted this form in the 

 Sydney Water-Supply, but have obtained the f rustules in quantity, 

 alive, from the swamps at Gardener's Road, Botany. It has 

 always been considered a fossil species. 



National Herbarium samples 108, 131, 142, 155. 



Var. Hekibaudii mihi. (PL Ivi., f.21, 22). 



Long. 80-134; lat. 6-8 /x. 



Syn., Stenopterohia anceps Heribaud, I.e., PL v., f.4, non Lewis. 

 Quite distinct in appearance from Lewis' form, into which it 

 develops. O. Miiller, in Bacillariales aus den Hochseen des Ries- 

 engebirges, T.iii., f.3o-37, gives illustrations of the structure. Cf. 

 also Gutwinski, De Algis in insula Java collectis, PL xL, f.G6. 



