122 BIOLOGY OF THE RICHMOND RIVER, 



Var. AUSTRALICA, n.var. (PI. v., f.l4). 



Valvse elliptico-lanceolatse, apices versus paullulo cuneatse, api- 

 cibus modice subrostratis ; lateribus in mediis valvis paullulo 

 deplanatis ; striis crassis baud punctatis, apices versus saepe 

 carentibus. 



Long. 76; lat. 28 fi. 



This variation combines in itself the characteristics of several 

 forms. There is a general resemblance, especially in the sub- 

 rostrate apex, to Tryhl. {Nav.) punctata; in size, however, it 

 agrees with Tryhl. Hantzschiana, while in shape it leans some- 

 what to T. ovata. 



Tryblionella cruciata, n.sp. (PI. v., f.l5). 



Valvse late-lineares, in medio inflatae, apicibus late-rotundatis. 

 Striis transversis, 8 in 10 /x, evddenter punctatis. 



Long. 48; lat. valv. centr. 1 6, ap. 1 1 /x. 



Only one frustule noted, and the only one, too, among numbers 

 of the others, in which the striae were distinctly punctate. If 

 Tryhl. punctata had been present, I would have made it a form 

 of that species. 



Lismore, all six forms (1); var. Victorice (1, 3, 6, 12); var. ovata 

 (1, 11,18); var. calida {3, 20). 



It is noticeable that these six forms of Tryblionella were all 

 found in the same sample(l) out of a few heads of Myriophyllum 

 gathered in one place. I cannot but consider them, therefore, 

 all forms of one species. On account of its punctate striae, how- 

 ever, Tr. cruciata has been kept separate. Following W. Smith, 

 and Grunow (originally), I have classed these forms together 

 under the old genus Tryhlionella. Why should Hantzschia and 

 Stenopterohia (whose forms much more resemble Nitzschice) be 

 separated from Nitzschia and these forms remain? The structure 

 of the frustule is on the lines of Surirella; the pseudoraphe, the 

 costae radiating more and more towards the apices where they 

 are often absent or more delicate, the submarginal keel 07i hoth 

 sides of the connecting zone (as also in Stenopterohia)^ the carinal 

 dots originating near the apices and getting more complex as 

 they approach the centre, all these remind one of Surirella. Also 



