| 1. | Lemmas hairy | E. gulliveri (QLD) E. gulliveri var. squarrulosa |
| Lemmas not hairy | 2 | |
| 2. | Spikelets 14-30mm long (excluding awns); lowest lemma 4-7mm long |
3 |
| Spikelets 2-11(-14)mm long (excluding awns); lowest lemma 1.5-4mm long |
5 | |
| 3. | Spikelets 25-30mm long | E. blakei (NT QLD) |
| Spikelets 14-20mm long | 4 | |
| 4. | Spikelets appressed to inflorescence branches |
E. danesii (NT WA QLD) E. appressa |
| Spikelets laxly dispersed | E. laxa (NT QLD) | |
| 5. | Lemmas distinctly scabrid all over | E. scabrida (NT WA QLD) |
| Lemmas smooth or slightly scabrous | 6 | |
| 6. | Spikelets 2-4mm wide | 7 |
| Spikelets 0.5-1.5mm wide | 8 | |
| 7. | Lemmas narrowly acuminate to aristate | E. anomala (QLD) |
| Lemmas with a distinct awn at least 2mm long |
E. confusa (NT QLD) | |
| 8. | Florets 8-25, all similar, mainly bisexual; awns 0.5-1.5mm long |
E. lasioclada (NT WA QLD) E. eragrostoides, E. subaristata, Ectrosiopsis lasioclada |
| Florets 2-9, lower bisexual or male, upper sterile; awns up to 12mm long |
9 | |
| 9. | Lowest lemma 3-3.5mm long | 10 |
| Lowest lemma 1.5-3mm long | 11 | |
| 10. | Perennial | E. schultzii var. schultzii (NT WA QLD) |
| Annual | E. schultzii var. annua (NT QLD) | |
| 11. | Spikelets 2-3mm long; inflorescence open |
E. agrostoides (NT WA QLD) |
| Spikelets 3-7mm long; inflorescence ±congested |
E. leporina (NT WA QLD) E. leporina var. longiglumis, E. leporina var. micrantha, E. leporina var. pauciflora, E. leporina var. spadicea |
Key to Ectrosia derived from Hubbard 1936; Nightingale & Weiller 2005
Taxonomic name: